Commit 7b0542d08b

Andrew Kelley <superjoe30@gmail.com>
2017-04-27 01:17:05
build system: consolidate duplicate code and more
* add ability to add assembly files when building an exe, obj, or lib * add implicit cast from `[N]T` to `?[]const T` (closes #343) * remove link_exe and link_lib in favor of allowing build_exe and build_lib support no root zig source file
1 parent 09bc4d6
src/all_types.hpp
@@ -1296,6 +1296,7 @@ struct CodeGen {
     LLVMBuilderRef builder;
     ZigLLVMDIBuilder *dbuilder;
     ZigLLVMDICompileUnit *compile_unit;
+    ZigLLVMDIFile *compile_unit_file;
 
     ZigList<Buf *> link_libs; // non-libc link libs
     // add -framework [name] args to linker
@@ -1468,6 +1469,7 @@ struct CodeGen {
 
     Buf global_asm;
     ZigList<Buf *> link_objects;
+    ZigList<Buf *> assembly_files;
 
     ZigList<TypeTableEntry *> name_table_enums;
 
src/analyze.cpp
@@ -2851,9 +2851,7 @@ void preview_use_decl(CodeGen *g, AstNode *node) {
     node->data.use.value = result;
 }
 
-ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package,
-        Buf *abs_full_path, Buf *src_dirname, Buf *src_basename, Buf *source_code)
-{
+ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package, Buf *abs_full_path, Buf *source_code) {
     if (g->verbose) {
         fprintf(stderr, "\nOriginal Source (%s):\n", buf_ptr(abs_full_path));
         fprintf(stderr, "----------------\n");
@@ -2894,7 +2892,10 @@ ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package,
         ast_print(stderr, import_entry->root, 0);
     }
 
-    // TODO: assert that src_basename has no '/' in it
+    Buf *src_dirname = buf_alloc();
+    Buf *src_basename = buf_alloc();
+    os_path_split(abs_full_path, src_dirname, src_basename);
+
     import_entry->di_file = ZigLLVMCreateFile(g->dbuilder, buf_ptr(src_basename), buf_ptr(src_dirname));
     g->import_table.put(abs_full_path, import_entry);
     g->import_queue.append(import_entry);
src/analyze.hpp
@@ -40,8 +40,7 @@ void find_libc_lib_path(CodeGen *g);
 bool type_has_bits(TypeTableEntry *type_entry);
 
 
-ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package,
-        Buf *abs_full_path, Buf *src_dirname, Buf *src_basename, Buf *source_code);
+ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package, Buf *abs_full_path, Buf *source_code);
 
 
 // TODO move these over, these used to be static
src/codegen.cpp
@@ -55,7 +55,7 @@ PackageTableEntry *new_package(const char *root_src_dir, const char *root_src_pa
     return entry;
 }
 
-CodeGen *codegen_create(Buf *root_source_dir, const ZigTarget *target) {
+CodeGen *codegen_create(Buf *root_src_path, const ZigTarget *target) {
     CodeGen *g = allocate<CodeGen>(1);
 
     codegen_add_time_event(g, "Initialize");
@@ -81,9 +81,17 @@ CodeGen *codegen_create(Buf *root_source_dir, const ZigTarget *target) {
     // reserve index 0 to indicate no error
     g->error_decls.append(nullptr);
 
-    g->root_package = new_package(buf_ptr(root_source_dir), "");
-    g->std_package = new_package(ZIG_STD_DIR, "index.zig");
-    g->root_package->package_table.put(buf_create_from_str("std"), g->std_package);
+    if (root_src_path) {
+        Buf *src_basename = buf_alloc();
+        Buf *src_dir = buf_alloc();
+        os_path_split(root_src_path, src_dir, src_basename);
+
+        g->root_package = new_package(buf_ptr(src_dir), buf_ptr(src_basename));
+        g->std_package = new_package(ZIG_STD_DIR, "index.zig");
+        g->root_package->package_table.put(buf_create_from_str("std"), g->std_package);
+    } else {
+        g->root_package = new_package(".", "");
+    }
     g->zig_std_dir = buf_create_from_str(ZIG_STD_DIR);
 
     g->zig_std_special_dir = buf_alloc();
@@ -757,7 +765,7 @@ static LLVMValueRef get_safety_crash_err_fn(CodeGen *g) {
 
 static void gen_debug_safety_crash_for_err(CodeGen *g, LLVMValueRef err_val) {
     LLVMValueRef safety_crash_err_fn = get_safety_crash_err_fn(g);
-    LLVMBuildCall(g->builder, safety_crash_err_fn, &err_val, 1, "");
+    ZigLLVMBuildCall(g->builder, safety_crash_err_fn, &err_val, 1, LLVMFastCallConv, false, "");
     LLVMBuildUnreachable(g->builder);
 }
 
@@ -3655,6 +3663,10 @@ static LLVMValueRef build_alloca(CodeGen *g, TypeTableEntry *type_entry, const c
 }
 
 static void do_code_gen(CodeGen *g) {
+    if (g->verbose) {
+        fprintf(stderr, "\nCode Generation:\n");
+        fprintf(stderr, "------------------\n");
+    }
     assert(!g->errors.length);
 
     codegen_add_time_event(g, "Code Generation");
@@ -4602,8 +4614,9 @@ static void define_builtin_compile_vars(CodeGen *g) {
     add_compile_var(g, "panic_implementation_provided", create_const_bool(g, false));
 }
 
-static void init(CodeGen *g, Buf *source_path) {
-    g->module = LLVMModuleCreateWithName(buf_ptr(source_path));
+static void init(CodeGen *g) {
+    assert(g->root_out_name);
+    g->module = LLVMModuleCreateWithName(buf_ptr(g->root_out_name));
 
     get_target_triple(&g->triple_str, &g->zig_target);
 
@@ -4674,23 +4687,25 @@ static void init(CodeGen *g, Buf *source_path) {
     g->const_void_val.type = g->builtin_types.entry_void;
 }
 
-void codegen_parseh(CodeGen *g, Buf *src_dirname, Buf *src_basename, Buf *source_code) {
+void codegen_parseh(CodeGen *g, Buf *full_path) {
     find_libc_include_path(g);
-    Buf *full_path = buf_alloc();
-    os_path_join(src_dirname, src_basename, full_path);
+
+    Buf *src_basename = buf_alloc();
+    Buf *src_dirname = buf_alloc();
+    os_path_split(full_path, src_dirname, src_basename);
 
     ImportTableEntry *import = allocate<ImportTableEntry>(1);
-    import->source_code = source_code;
+    import->source_code = nullptr;
     import->path = full_path;
     g->root_import = import;
     import->decls_scope = create_decls_scope(nullptr, nullptr, nullptr, import);
 
-    init(g, full_path);
+    init(g);
 
     import->di_file = ZigLLVMCreateFile(g->dbuilder, buf_ptr(src_basename), buf_ptr(src_dirname));
 
     ZigList<ErrorMsg *> errors = {0};
-    int err = parse_h_buf(import, &errors, source_code, g, nullptr);
+    int err = parse_h_file(import, &errors, buf_ptr(full_path), g, nullptr);
     if (err) {
         fprintf(stderr, "unable to parse .h file: %s\n", err_str(err));
         exit(1);
@@ -4719,7 +4734,7 @@ static ImportTableEntry *add_special_code(CodeGen *g, PackageTableEntry *package
         zig_panic("unable to open '%s': %s", buf_ptr(&path_to_code_src), err_str(err));
     }
 
-    return add_source_file(g, package, abs_full_path, g->zig_std_special_dir, code_basename, import_code);
+    return add_source_file(g, package, abs_full_path, import_code);
 }
 
 static PackageTableEntry *create_bootstrap_pkg(CodeGen *g) {
@@ -4736,23 +4751,27 @@ static PackageTableEntry *create_zigrt_pkg(CodeGen *g) {
     return package;
 }
 
-void codegen_add_root_code(CodeGen *g, Buf *src_dir, Buf *src_basename, Buf *source_code) {
-    codegen_add_time_event(g, "Semantic Analysis");
-
-    Buf source_path = BUF_INIT;
-    os_path_join(src_dir, src_basename, &source_path);
+static void gen_root_source(CodeGen *g) {
+    if (buf_len(&g->root_package->root_src_path) == 0)
+        return;
 
-    buf_init_from_buf(&g->root_package->root_src_path, src_basename);
+    codegen_add_time_event(g, "Semantic Analysis");
 
-    init(g, &source_path);
+    Buf *rel_full_path = buf_alloc();
+    os_path_join(&g->root_package->root_src_dir, &g->root_package->root_src_path, rel_full_path);
 
     Buf *abs_full_path = buf_alloc();
     int err;
-    if ((err = os_path_real(&source_path, abs_full_path))) {
-        zig_panic("unable to open '%s': %s", buf_ptr(&source_path), err_str(err));
+    if ((err = os_path_real(rel_full_path, abs_full_path))) {
+        zig_panic("unable to open '%s': %s", buf_ptr(rel_full_path), err_str(err));
+    }
+
+    Buf *source_code = buf_alloc();
+    if ((err = os_fetch_file_path(rel_full_path, source_code))) {
+        zig_panic("unable to open '%s': %s", buf_ptr(rel_full_path), err_str(err));
     }
 
-    g->root_import = add_source_file(g, g->root_package, abs_full_path, src_dir, src_basename, source_code);
+    g->root_import = add_source_file(g, g->root_package, abs_full_path, source_code);
 
     assert(g->root_out_name);
     assert(g->out_type != OutTypeUnknown);
@@ -4787,27 +4806,33 @@ void codegen_add_root_code(CodeGen *g, Buf *src_dir, Buf *src_basename, Buf *sou
         exit(1);
     }
 
-    if (g->verbose) {
-        fprintf(stderr, "\nCode Generation:\n");
-        fprintf(stderr, "------------------\n");
-
-    }
-
-    do_code_gen(g);
 }
 
-void codegen_add_root_assembly(CodeGen *g, Buf *src_dir, Buf *src_basename, Buf *source_code) {
-    Buf source_path = BUF_INIT;
-    os_path_join(src_dir, src_basename, &source_path);
+void codegen_add_assembly(CodeGen *g, Buf *path) {
+    g->assembly_files.append(path);
+}
 
-    init(g, &source_path);
+static void gen_global_asm(CodeGen *g) {
+    Buf contents = BUF_INIT;
+    int err;
+    for (size_t i = 0; i < g->assembly_files.length; i += 1) {
+        Buf *asm_file = g->assembly_files.at(i);
+        if ((err = os_fetch_file_path(asm_file, &contents))) {
+            zig_panic("Unable to read %s: %s", buf_ptr(asm_file), err_str(err));
+        }
+        if (g->zig_target.arch.arch == ZigLLVM_x86 || g->zig_target.arch.arch == ZigLLVM_x86_64) {
+            buf_append_str(&g->global_asm, ".intel_syntax noprefix\n");
+        }
+        buf_append_buf(&g->global_asm, &contents);
+    }
+}
 
-    assert(g->root_out_name);
+void codegen_build(CodeGen *g) {
     assert(g->out_type != OutTypeUnknown);
+    init(g);
 
-    buf_init_from_str(&g->global_asm, ".intel_syntax noprefix\n");
-    buf_append_buf(&g->global_asm, source_code);
-
+    gen_global_asm(g);
+    gen_root_source(g);
     do_code_gen(g);
 }
 
src/codegen.hpp
@@ -14,7 +14,7 @@
 
 #include <stdio.h>
 
-CodeGen *codegen_create(Buf *root_source_dir, const ZigTarget *target);
+CodeGen *codegen_create(Buf *root_src_path, const ZigTarget *target);
 
 void codegen_set_clang_argv(CodeGen *codegen, const char **args, size_t len);
 void codegen_set_is_release(CodeGen *codegen, bool is_release);
@@ -49,13 +49,13 @@ void codegen_set_test_name_prefix(CodeGen *g, Buf *prefix);
 void codegen_set_lib_version(CodeGen *g, size_t major, size_t minor, size_t patch);
 void codegen_add_time_event(CodeGen *g, const char *name);
 void codegen_print_timing_report(CodeGen *g, FILE *f);
+void codegen_build(CodeGen *g);
 
 PackageTableEntry *new_package(const char *root_src_dir, const char *root_src_path);
-void codegen_add_root_code(CodeGen *g, Buf *source_dir, Buf *source_basename, Buf *source_code);
-void codegen_add_root_assembly(CodeGen *g, Buf *source_dir, Buf *source_basename, Buf *source_code);
+void codegen_add_assembly(CodeGen *g, Buf *path);
 void codegen_add_object(CodeGen *g, Buf *object_path);
 
-void codegen_parseh(CodeGen *g, Buf *src_dirname, Buf *src_basename, Buf *source_code);
+void codegen_parseh(CodeGen *g, Buf *path);
 void codegen_render_ast(CodeGen *g, FILE *f, int indent_size);
 
 void codegen_generate_h_file(CodeGen *g);
src/ir.cpp
@@ -6043,6 +6043,21 @@ static ImplicitCastMatchResult ir_types_match_with_implicit_cast(IrAnalyze *ira,
         }
     }
 
+    // implicit [N]T to ?[]const N
+    if (expected_type->id == TypeTableEntryIdMaybe &&
+        is_slice(expected_type->data.maybe.child_type) &&
+        actual_type->id == TypeTableEntryIdArray)
+    {
+        TypeTableEntry *ptr_type =
+            expected_type->data.maybe.child_type->data.structure.fields[slice_ptr_index].type_entry;
+        assert(ptr_type->id == TypeTableEntryIdPointer);
+        if ((ptr_type->data.pointer.is_const || actual_type->data.array.len == 0) &&
+                types_match_const_cast_only(ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
+        {
+            return ImplicitCastMatchResultYes;
+        }
+    }
+
     // implicit number literal to typed number
     // implicit number literal to &const integer
     if (actual_type->id == TypeTableEntryIdNumLitFloat ||
@@ -7093,6 +7108,29 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         }
     }
 
+    // explicit cast from [N]T to ?[]const N
+    if (wanted_type->id == TypeTableEntryIdMaybe &&
+        is_slice(wanted_type->data.maybe.child_type) &&
+        actual_type->id == TypeTableEntryIdArray)
+    {
+        TypeTableEntry *ptr_type =
+            wanted_type->data.maybe.child_type->data.structure.fields[slice_ptr_index].type_entry;
+        assert(ptr_type->id == TypeTableEntryIdPointer);
+        if ((ptr_type->data.pointer.is_const || actual_type->data.array.len == 0) &&
+                types_match_const_cast_only(ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
+        {
+            IrInstruction *cast1 = ir_analyze_cast(ira, source_instr, wanted_type->data.maybe.child_type, value);
+            if (type_is_invalid(cast1->value.type))
+                return ira->codegen->invalid_instruction;
+
+            IrInstruction *cast2 = ir_analyze_cast(ira, source_instr, wanted_type, cast1);
+            if (type_is_invalid(cast2->value.type))
+                return ira->codegen->invalid_instruction;
+
+            return cast2;
+        }
+    }
+
     // explicit cast from []T to []u8 or []u8 to []T
     if (is_slice(wanted_type) && is_slice(actual_type) &&
         (is_u8(wanted_type->data.structure.fields[slice_ptr_index].type_entry->data.pointer.child_type) ||
@@ -10880,8 +10918,7 @@ static TypeTableEntry *ir_analyze_instruction_import(IrAnalyze *ira, IrInstructi
             return ira->codegen->builtin_types.entry_invalid;
         }
     }
-    ImportTableEntry *target_import = add_source_file(ira->codegen, target_package,
-            abs_full_path, search_dir, import_target_path, import_code);
+    ImportTableEntry *target_import = add_source_file(ira->codegen, target_package, abs_full_path, import_code);
 
     scan_decls(ira->codegen, target_import->decls_scope, target_import->root);
 
src/link.cpp
@@ -33,9 +33,11 @@ static const char *get_libc_static_file(CodeGen *g, const char *file) {
 
 static Buf *build_o(CodeGen *parent_gen, const char *oname) {
     Buf *source_basename = buf_sprintf("%s.zig", oname);
+    Buf *full_path = buf_alloc();
+    os_path_join(parent_gen->zig_std_special_dir, source_basename, full_path);
 
     ZigTarget *child_target = parent_gen->is_native_target ? nullptr : &parent_gen->zig_target;
-    CodeGen *child_gen = codegen_create(parent_gen->zig_std_special_dir, child_target);
+    CodeGen *child_gen = codegen_create(full_path, child_target);
     child_gen->link_libc = parent_gen->link_libc;
 
     child_gen->link_libs.resize(parent_gen->link_libs.length);
@@ -60,15 +62,7 @@ static Buf *build_o(CodeGen *parent_gen, const char *oname) {
     codegen_set_mmacosx_version_min(child_gen, parent_gen->mmacosx_version_min);
     codegen_set_mios_version_min(child_gen, parent_gen->mios_version_min);
 
-    Buf *full_path = buf_alloc();
-    os_path_join(parent_gen->zig_std_special_dir, source_basename, full_path);
-
-    Buf source_code = BUF_INIT;
-    if (os_fetch_file_path(full_path, &source_code)) {
-        zig_panic("unable to fetch file: %s\n", buf_ptr(full_path));
-    }
-
-    codegen_add_root_code(child_gen, parent_gen->zig_std_special_dir, source_basename, &source_code);
+    codegen_build(child_gen);
     const char *o_ext = target_o_file_ext(&child_gen->zig_target);
     Buf *o_out = buf_sprintf("%s%s", oname, o_ext);
     codegen_link(child_gen, buf_ptr(o_out));
src/main.cpp
@@ -19,29 +19,19 @@
 static int usage(const char *arg0) {
     fprintf(stderr, "Usage: %s [command] [options]\n"
         "Commands:\n"
-        "  asm [source]                 create object from assembly\n"
         "  build                        build project from build.zig\n"
-        "  build_exe [source]           create executable from source\n"
-        "  build_lib [source]           create library from source\n"
-        "  build_obj [source]           create object from source\n"
-        "  link_exe [objects]           create executable from objects\n"
-        "  link_lib [objects]           create library from objects\n"
+        "  build_exe [source]           create executable from source or object files\n"
+        "  build_lib [source]           create library from source or object files\n"
+        "  build_obj [source]           create object from source or assembly\n"
         "  parseh [source]              convert a c header file to zig extern declarations\n"
         "  targets                      list available compilation targets\n"
         "  test [source]                create and run a test build\n"
         "  version                      print version number and exit\n"
-        "Options:\n"
-        "  --ar-path [path]             set the path to ar\n"
+        "Compile Options:\n"
+        "  --assembly [source]          add assembly file to build\n"
         "  --color [auto|off|on]        enable or disable colored error messages\n"
-        "  --dynamic-linker [path]      set the path to ld.so\n"
-        "  --each-lib-rpath             add rpath for each used dynamic library\n"
-        "  --ld-path [path]             set the path to the linker\n"
+        "  --enable-timing-info         print timing diagnostics\n"
         "  --libc-include-dir [path]    directory where libc stdlib.h resides\n"
-        "  --libc-lib-dir [path]        directory where libc crt1.o resides\n"
-        "  --libc-static-lib-dir [path] directory where libc crtbegin.o resides\n"
-        "  --library [lib]              link against lib\n"
-        "  --library-path [dir]         add a directory to the library search path\n"
-        "  --linker-script [path]       use a custom linker script\n"
         "  --name [name]                override output name\n"
         "  --output [file]              override destination path\n"
         "  --release                    build with optimizations on and debug protection off\n"
@@ -52,26 +42,34 @@ static int usage(const char *arg0) {
         "  --target-os [name]           specify target operating system\n"
         "  --verbose                    turn on compiler debug output\n"
         "  --zig-std-dir [path]         directory where zig standard library resides\n"
-        "  -L[dir]                      alias for --library-path\n"
         "  -dirafter [dir]              same as -isystem but do it last\n"
-        "  -framework [name]            (darwin only) link against framework\n"
         "  -isystem [dir]               add additional search path for other .h files\n"
-        "  -mconsole                    (windows only) --subsystem console to the linker\n"
-        "  -mios-version-min [ver]      (darwin only) set iOS deployment target\n"
-        "  -mlinker-version [ver]       (darwin only) override linker version\n"
-        "  -mmacosx-version-min [ver]   (darwin only) set Mac OS X deployment target\n"
-        "  -municode                    (windows only) link with unicode\n"
-        "  -mwindows                    (windows only) --subsystem windows to the linker\n"
+        "Link Options:\n"
+        "  --ar-path [path]             set the path to ar\n"
+        "  --dynamic-linker [path]      set the path to ld.so\n"
+        "  --each-lib-rpath             add rpath for each used dynamic library\n"
+        "  --libc-lib-dir [path]        directory where libc crt1.o resides\n"
+        "  --libc-static-lib-dir [path] directory where libc crtbegin.o resides\n"
+        "  --library [lib]              link against lib\n"
+        "  --library-path [dir]         add a directory to the library search path\n"
+        "  --linker-script [path]       use a custom linker script\n"
+        "  --object [obj]               add object file to build\n"
+        "  -L[dir]                      alias for --library-path\n"
         "  -rdynamic                    add all symbols to the dynamic symbol table\n"
         "  -rpath [path]                add directory to the runtime library search path\n"
-        "  --enable-timing-info         print timing diagnostics\n"
+        "  -mconsole                    (windows) --subsystem console to the linker\n"
+        "  -mwindows                    (windows) --subsystem windows to the linker\n"
+        "  -municode                    (windows) link with unicode\n"
+        "  -framework [name]            (darwin) link against framework\n"
+        "  -mios-version-min [ver]      (darwin) set iOS deployment target\n"
+        "  -mlinker-version [ver]       (darwin) override linker version\n"
+        "  -mmacosx-version-min [ver]   (darwin) set Mac OS X deployment target\n"
+        "  --ver-major [ver]            dynamic library semver major version\n"
+        "  --ver-minor [ver]            dynamic library semver minor version\n"
+        "  --ver-patch [ver]            dynamic library semver patch version\n"
         "Test Options:\n"
         "  --test-filter [text]         skip tests that do not match filter\n"
         "  --test-name-prefix [text]    add prefix to all tests\n"
-        "Dynamic Library Options:\n"
-        "  --ver-major [ver]            semver major version\n"
-        "  --ver-minor [ver]            semver minor version\n"
-        "  --ver-patch [ver]            semver patch version\n"
     , arg0);
     return EXIT_FAILURE;
 }
@@ -117,8 +115,6 @@ enum Cmd {
     CmdVersion,
     CmdParseH,
     CmdTargets,
-    CmdAsm,
-    CmdLink,
 };
 
 int main(int argc, char **argv) {
@@ -159,6 +155,7 @@ int main(int argc, char **argv) {
     ZigList<const char *> rpath_list = {0};
     bool each_lib_rpath = false;
     ZigList<const char *> objects = {0};
+    ZigList<const char *> asm_files = {0};
     const char *test_filter = nullptr;
     const char *test_name_prefix = nullptr;
     size_t ver_major = 0;
@@ -197,16 +194,7 @@ int main(int argc, char **argv) {
             }
         }
 
-
-        Buf root_source_dir = BUF_INIT;
-        Buf root_source_code = BUF_INIT;
-        Buf root_source_name = BUF_INIT;
-        os_path_split(build_runner_path, &root_source_dir, &root_source_name);
-        if ((err = os_fetch_file_path(build_runner_path, &root_source_code))) {
-            fprintf(stderr, "unable to open '%s': %s\n", buf_ptr(build_runner_path), err_str(err));
-            return 1;
-        }
-        CodeGen *g = codegen_create(&root_source_dir, nullptr);
+        CodeGen *g = codegen_create(build_runner_path, nullptr);
         codegen_set_out_name(g, buf_create_from_str("build"));
         codegen_set_out_type(g, OutTypeExe);
         codegen_set_verbose(g, verbose);
@@ -256,7 +244,7 @@ int main(int argc, char **argv) {
         PackageTableEntry *build_pkg = new_package(buf_ptr(&build_file_dirname), buf_ptr(&build_file_basename));
         build_pkg->package_table.put(buf_create_from_str("std"), g->std_package);
         g->root_package->package_table.put(buf_create_from_str("@build"), build_pkg);
-        codegen_add_root_code(g, &root_source_dir, &root_source_name, &root_source_code);
+        codegen_build(g);
         codegen_link(g, "build");
 
         Termination term;
@@ -339,6 +327,10 @@ int main(int argc, char **argv) {
                     lib_dirs.append(argv[i]);
                 } else if (strcmp(arg, "--library") == 0) {
                     link_libs.append(argv[i]);
+                } else if (strcmp(arg, "--object") == 0) {
+                    objects.append(argv[i]);
+                } else if (strcmp(arg, "--assembly") == 0) {
+                    asm_files.append(argv[i]);
                 } else if (strcmp(arg, "--target-arch") == 0) {
                     target_arch = argv[i];
                 } else if (strcmp(arg, "--target-os") == 0) {
@@ -382,12 +374,6 @@ int main(int argc, char **argv) {
             } else if (strcmp(arg, "build_lib") == 0) {
                 cmd = CmdBuild;
                 out_type = OutTypeLib;
-            } else if (strcmp(arg, "link_lib") == 0) {
-                cmd = CmdLink;
-                out_type = OutTypeLib;
-            } else if (strcmp(arg, "link_exe") == 0) {
-                cmd = CmdLink;
-                out_type = OutTypeExe;
             } else if (strcmp(arg, "version") == 0) {
                 cmd = CmdVersion;
             } else if (strcmp(arg, "parseh") == 0) {
@@ -396,8 +382,6 @@ int main(int argc, char **argv) {
                 cmd = CmdTest;
             } else if (strcmp(arg, "targets") == 0) {
                 cmd = CmdTargets;
-            } else if (strcmp(arg, "asm") == 0) {
-                cmd = CmdAsm;
             } else {
                 fprintf(stderr, "Unrecognized command: %s\n", arg);
                 return usage(arg0);
@@ -407,16 +391,12 @@ int main(int argc, char **argv) {
                 case CmdBuild:
                 case CmdParseH:
                 case CmdTest:
-                case CmdAsm:
                     if (!in_file) {
                         in_file = arg;
                     } else {
                         return usage(arg0);
                     }
                     break;
-                case CmdLink:
-                    objects.append(arg);
-                    break;
                 case CmdVersion:
                 case CmdTargets:
                     return usage(arg0);
@@ -430,25 +410,19 @@ int main(int argc, char **argv) {
     case CmdBuild:
     case CmdParseH:
     case CmdTest:
-    case CmdAsm:
-    case CmdLink:
         {
-            bool one_source_input = (cmd == CmdBuild || cmd == CmdParseH || cmd == CmdTest || cmd == CmdAsm);
-            if (one_source_input) {
-                if (!in_file) {
-                    fprintf(stderr, "Expected source file argument.\n");
-                    return usage(arg0);
-                }
-            } else if (cmd == CmdLink) {
-                if (objects.length == 0) {
-                    fprintf(stderr, "Expected one or more object arguments.\n");
-                    return usage(arg0);
-                }
-            } else {
-                zig_unreachable();
+            if (cmd == CmdBuild && !in_file && objects.length == 0 && asm_files.length == 0) {
+                fprintf(stderr, "Expected source file argument or at least one --object or --assembly argument.\n");
+                return usage(arg0);
+            } else if ((cmd == CmdParseH || cmd == CmdTest) && !in_file) {
+                fprintf(stderr, "Expected source file argument.\n");
+                return usage(arg0);
+            } else if (cmd == CmdBuild && out_type == OutTypeObj && objects.length != 0) {
+                fprintf(stderr, "When building an object file, --object arguments are invalid.\n");
+                return usage(arg0);
             }
 
-            assert((cmd != CmdBuild && cmd != CmdLink) || out_type != OutTypeUnknown);
+            assert(cmd != CmdBuild || out_type != OutTypeUnknown);
 
             init_all_targets();
 
@@ -479,45 +453,22 @@ int main(int argc, char **argv) {
                 }
             }
 
-            bool need_name = (cmd == CmdBuild || cmd == CmdAsm || cmd == CmdLink || cmd == CmdParseH);
+            bool need_name = (cmd == CmdBuild || cmd == CmdParseH);
 
-            Buf in_file_buf = BUF_INIT;
-
-            Buf root_source_dir = BUF_INIT;
-            Buf root_source_code = BUF_INIT;
-            Buf root_source_name = BUF_INIT;
+            Buf *in_file_buf = nullptr;
 
             Buf *buf_out_name = (cmd == CmdTest) ? buf_create_from_str("test") :
                 (out_name == nullptr) ? nullptr : buf_create_from_str(out_name);
 
-            if (one_source_input) {
-                buf_init_from_str(&in_file_buf, in_file);
-
-                if (buf_eql_str(&in_file_buf, "-")) {
-                    os_get_cwd(&root_source_dir);
-                    if ((err = os_fetch_file(stdin, &root_source_code))) {
-                        fprintf(stderr, "unable to read stdin: %s\n", err_str(err));
-                        return 1;
-                    }
-                    buf_init_from_str(&root_source_name, "");
+            if (in_file) {
+                in_file_buf = buf_create_from_str(in_file);
 
-                } else {
-                    os_path_split(&in_file_buf, &root_source_dir, &root_source_name);
-                    if ((err = os_fetch_file_path(buf_create_from_str(in_file), &root_source_code))) {
-                        fprintf(stderr, "unable to open '%s': %s\n", in_file, err_str(err));
-                        return 1;
-                    }
-
-                    if (need_name && buf_out_name == nullptr) {
-                        buf_out_name = buf_alloc();
-                        Buf ext_name = BUF_INIT;
-                        os_path_extname(&root_source_name, buf_out_name, &ext_name);
-                    }
+                if (need_name && buf_out_name == nullptr) {
+                    Buf basename = BUF_INIT;
+                    os_path_split(in_file_buf, nullptr, &basename);
+                    buf_out_name = buf_alloc();
+                    os_path_extname(&basename, buf_out_name, nullptr);
                 }
-            } else if (cmd == CmdLink) {
-                os_get_cwd(&root_source_dir);
-            } else {
-                zig_unreachable();
             }
 
             if (need_name && buf_out_name == nullptr) {
@@ -525,7 +476,10 @@ int main(int argc, char **argv) {
                 return usage(arg0);
             }
 
-            CodeGen *g = codegen_create(&root_source_dir, target);
+            Buf *zig_root_source_file = (cmd == CmdParseH) ? nullptr : in_file_buf;
+
+            CodeGen *g = codegen_create(zig_root_source_file, target);
+            codegen_set_out_name(g, buf_out_name);
             codegen_set_lib_version(g, ver_major, ver_minor, ver_patch);
             codegen_set_is_release(g, is_release_build);
             codegen_set_is_test(g, cmd == CmdTest);
@@ -536,14 +490,11 @@ int main(int argc, char **argv) {
             codegen_set_clang_argv(g, clang_argv.items, clang_argv.length);
             codegen_set_strip(g, strip);
             codegen_set_is_static(g, is_static);
-            if (cmd == CmdAsm) {
-                codegen_set_out_type(g, OutTypeObj);
-            } else if (out_type != OutTypeUnknown) {
+            if (out_type != OutTypeUnknown) {
                 codegen_set_out_type(g, out_type);
             } else if (cmd == CmdTest) {
                 codegen_set_out_type(g, OutTypeExe);
             }
-            codegen_set_out_name(g, buf_out_name);
             if (libc_lib_dir)
                 codegen_set_libc_lib_dir(g, buf_create_from_str(libc_lib_dir));
             if (libc_static_lib_dir)
@@ -598,33 +549,25 @@ int main(int argc, char **argv) {
             }
 
             if (cmd == CmdBuild) {
-                codegen_add_root_code(g, &root_source_dir, &root_source_name, &root_source_code);
-                codegen_link(g, out_file);
-                if (timing_info)
-                    codegen_print_timing_report(g, stderr);
-                return EXIT_SUCCESS;
-            } else if (cmd == CmdLink) {
                 for (size_t i = 0; i < objects.length; i += 1) {
                     codegen_add_object(g, buf_create_from_str(objects.at(i)));
                 }
-                codegen_link(g, out_file);
-                if (timing_info)
-                    codegen_print_timing_report(g, stderr);
-                return EXIT_SUCCESS;
-            } else if (cmd == CmdAsm) {
-                codegen_add_root_assembly(g, &root_source_dir, &root_source_name, &root_source_code);
+                for (size_t i = 0; i < asm_files.length; i += 1) {
+                    codegen_add_assembly(g, buf_create_from_str(asm_files.at(i)));
+                }
+                codegen_build(g);
                 codegen_link(g, out_file);
                 if (timing_info)
                     codegen_print_timing_report(g, stderr);
                 return EXIT_SUCCESS;
             } else if (cmd == CmdParseH) {
-                codegen_parseh(g, &root_source_dir, &root_source_name, &root_source_code);
+                codegen_parseh(g, in_file_buf);
                 ast_render_decls(g, stdout, 4, g->root_import);
                 if (timing_info)
                     codegen_print_timing_report(g, stderr);
                 return EXIT_SUCCESS;
             } else if (cmd == CmdTest) {
-                codegen_add_root_code(g, &root_source_dir, &root_source_name, &root_source_code);
+                codegen_build(g);
                 codegen_link(g, "./test");
                 ZigList<const char *> args = {0};
                 Termination term;
src/os.cpp
@@ -146,24 +146,28 @@ void os_path_split(Buf *full_path, Buf *out_dirname, Buf *out_basename) {
 
 void os_path_extname(Buf *full_path, Buf *out_basename, Buf *out_extname) {
     if (buf_len(full_path) == 0) {
-        buf_init_from_str(out_basename, "");
-        buf_init_from_str(out_extname, "");
+        if (out_basename) buf_init_from_str(out_basename, "");
+        if (out_extname) buf_init_from_str(out_extname, "");
         return;
     }
     size_t i = buf_len(full_path) - 1;
     while (true) {
         if (buf_ptr(full_path)[i] == '.') {
-            buf_resize(out_basename, 0);
-            buf_append_mem(out_basename, buf_ptr(full_path), i);
+            if (out_basename) {
+                buf_resize(out_basename, 0);
+                buf_append_mem(out_basename, buf_ptr(full_path), i);
+            }
 
-            buf_resize(out_extname, 0);
-            buf_append_mem(out_extname, buf_ptr(full_path) + i, buf_len(full_path) - i);
+            if (out_extname) {
+                buf_resize(out_extname, 0);
+                buf_append_mem(out_extname, buf_ptr(full_path) + i, buf_len(full_path) - i);
+            }
             return;
         }
 
         if (i == 0) {
-            buf_init_from_buf(out_basename, full_path);
-            buf_init_from_str(out_extname, "");
+            if (out_basename) buf_init_from_buf(out_basename, full_path);
+            if (out_extname) buf_init_from_str(out_extname, "");
             return;
         }
         i -= 1;
std/build.zig
@@ -120,28 +120,22 @@ pub const Builder = struct {
         self.lib_dir = %%os.path.join(self.allocator, self.prefix, "lib");
     }
 
-    pub fn addExecutable(self: &Builder, name: []const u8, root_src: []const u8) -> &LibOrExeStep {
-        const exe = %%self.allocator.create(LibOrExeStep);
-        *exe = LibOrExeStep.initExecutable(self, name, root_src);
-        return exe;
+    pub fn addExecutable(self: &Builder, name: []const u8, root_src: ?[]const u8) -> &LibExeObjStep {
+        return LibExeObjStep.createExecutable(self, name, root_src);
     }
 
-    pub fn addObject(self: &Builder, name: []const u8, root_src: []const u8) -> &ObjectStep {
-        const obj_step = %%self.allocator.create(ObjectStep);
-        *obj_step = ObjectStep.init(self, name, root_src);
-        return obj_step;
+    pub fn addObject(self: &Builder, name: []const u8, root_src: []const u8) -> &LibExeObjStep {
+        return LibExeObjStep.createObject(self, name, root_src);
     }
 
-    pub fn addSharedLibrary(self: &Builder, name: []const u8, root_src: []const u8, ver: &const Version) -> &LibOrExeStep {
-        const lib_step = %%self.allocator.create(LibOrExeStep);
-        *lib_step = LibOrExeStep.initSharedLibrary(self, name, root_src, ver);
-        return lib_step;
+    pub fn addSharedLibrary(self: &Builder, name: []const u8, root_src: ?[]const u8,
+        ver: &const Version) -> &LibExeObjStep
+    {
+        return LibExeObjStep.createSharedLibrary(self, name, root_src, ver);
     }
 
-    pub fn addStaticLibrary(self: &Builder, name: []const u8, root_src: []const u8) -> &LibOrExeStep {
-        const lib_step = %%self.allocator.create(LibOrExeStep);
-        *lib_step = LibOrExeStep.initStaticLibrary(self, name, root_src);
-        return lib_step;
+    pub fn addStaticLibrary(self: &Builder, name: []const u8, root_src: ?[]const u8) -> &LibExeObjStep {
+        return LibExeObjStep.createStaticLibrary(self, name, root_src);
     }
 
     pub fn addTest(self: &Builder, root_src: []const u8) -> &TestStep {
@@ -150,28 +144,10 @@ pub const Builder = struct {
         return test_step;
     }
 
-    pub fn addAssemble(self: &Builder, name: []const u8, src: []const u8) -> &AsmStep {
-        const asm_step = %%self.allocator.create(AsmStep);
-        *asm_step = AsmStep.init(self, name, src);
-        return asm_step;
-    }
-
-    pub fn addLinkExecutable(self: &Builder, name: []const u8) -> &LinkStep {
-        const exe = %%self.allocator.create(LinkStep);
-        *exe = LinkStep.initExecutable(self, name);
-        return exe;
-    }
-
-    pub fn addLinkStaticLibrary(self: &Builder, name: []const u8) -> &LinkStep {
-        const exe = %%self.allocator.create(LinkStep);
-        *exe = LinkStep.initStaticLibrary(self, name);
-        return exe;
-    }
-
-    pub fn addLinkSharedLibrary(self: &Builder, name: []const u8, ver: &const Version) -> &LinkStep {
-        const exe = %%self.allocator.create(LinkStep);
-        *exe = LinkStep.initSharedLibrary(self, name, ver);
-        return exe;
+    pub fn addAssemble(self: &Builder, name: []const u8, src: []const u8) -> &LibExeObjStep {
+        const obj_step = LibExeObjStep.createObject(self, name, null);
+        obj_step.addAssemblyFile(src);
+        return obj_step;
     }
 
     pub fn addCStaticLibrary(self: &Builder, name: []const u8) -> &CLibrary {
@@ -635,10 +611,10 @@ const LinkerScript = enum {
     Path: []const u8,
 };
 
-pub const LibOrExeStep = struct {
+pub const LibExeObjStep = struct {
     step: Step,
     builder: &Builder,
-    root_src: []const u8,
+    root_src: ?[]const u8,
     name: []const u8,
     target: Target,
     linker_script: LinkerScript,
@@ -652,30 +628,45 @@ pub const LibOrExeStep = struct {
     out_filename: []const u8,
     out_filename_major_only: []const u8,
     out_filename_name_only: []const u8,
+    object_files: List([]const u8),
+    assembly_files: List([]const u8),
 
     const Kind = enum {
         Exe,
         Lib,
+        Obj,
     };
 
-    pub fn initExecutable(builder: &Builder, name: []const u8, root_src: []const u8) -> LibOrExeStep {
-        return initExtraArgs(builder, name, root_src, Kind.Exe, false, builder.version(0, 0, 0));
+    pub fn createSharedLibrary(builder: &Builder, name: []const u8, root_src: ?[]const u8,
+        ver: &const Version) -> &LibExeObjStep
+    {
+        const self = %%builder.allocator.create(LibExeObjStep);
+        *self = initExtraArgs(builder, name, root_src, Kind.Lib, false, ver);
+        return self;
     }
 
-    pub fn initSharedLibrary(builder: &Builder, name: []const u8, root_src: []const u8,
-        ver: &const Version) -> LibOrExeStep
-    {
-        return initExtraArgs(builder, name, root_src, Kind.Lib, false, ver);
+    pub fn createStaticLibrary(builder: &Builder, name: []const u8, root_src: ?[]const u8) -> &LibExeObjStep {
+        const self = %%builder.allocator.create(LibExeObjStep);
+        *self = initExtraArgs(builder, name, root_src, Kind.Lib, true, builder.version(0, 0, 0));
+        return self;
     }
 
-    pub fn initStaticLibrary(builder: &Builder, name: []const u8, root_src: []const u8) -> LibOrExeStep {
-        return initExtraArgs(builder, name, root_src, Kind.Lib, true, builder.version(0, 0, 0));
+    pub fn createObject(builder: &Builder, name: []const u8, root_src: []const u8) -> &LibExeObjStep {
+        const self = %%builder.allocator.create(LibExeObjStep);
+        *self = initExtraArgs(builder, name, root_src, Kind.Obj, false, builder.version(0, 0, 0));
+        return self;
     }
 
-    fn initExtraArgs(builder: &Builder, name: []const u8, root_src: []const u8, kind: Kind,
-        static: bool, ver: &const Version) -> LibOrExeStep
+    pub fn createExecutable(builder: &Builder, name: []const u8, root_src: ?[]const u8) -> &LibExeObjStep {
+        const self = %%builder.allocator.create(LibExeObjStep);
+        *self = initExtraArgs(builder, name, root_src, Kind.Exe, false, builder.version(0, 0, 0));
+        return self;
+    }
+
+    fn initExtraArgs(builder: &Builder, name: []const u8, root_src: ?[]const u8, kind: Kind,
+        static: bool, ver: &const Version) -> LibExeObjStep
     {
-        var self = LibOrExeStep {
+        var self = LibExeObjStep {
             .builder = builder,
             .verbose = false,
             .release = false,
@@ -692,13 +683,18 @@ pub const LibOrExeStep = struct {
             .out_filename = undefined,
             .out_filename_major_only = undefined,
             .out_filename_name_only = undefined,
+            .object_files = List([]const u8).init(builder.allocator),
+            .assembly_files = List([]const u8).init(builder.allocator),
         };
         self.computeOutFileNames();
         return self;
     }
 
-    fn computeOutFileNames(self: &LibOrExeStep) {
+    fn computeOutFileNames(self: &LibExeObjStep) {
         switch (self.kind) {
+            Kind.Obj => {
+                self.out_filename = self.builder.fmt("{}{}", self.name, self.target.oFileExt());
+            },
             Kind.Exe => {
                 self.out_filename = self.builder.fmt("{}{}", self.name, self.target.exeFileExt());
             },
@@ -715,7 +711,7 @@ pub const LibOrExeStep = struct {
         }
     }
 
-    pub fn setTarget(self: &LibOrExeStep, target_arch: Arch, target_os: Os, target_environ: Environ) {
+    pub fn setTarget(self: &LibExeObjStep, target_arch: Arch, target_os: Os, target_environ: Environ) {
         self.target = Target.Cross {
             CrossTarget {
                 .arch = target_arch,
@@ -723,414 +719,49 @@ pub const LibOrExeStep = struct {
                 .environ = target_environ,
             }
         };
+        self.computeOutFileNames();
     }
 
-    /// LibOrExeStep keeps a reference to script for its lifetime or until this function
+    /// LibExeObjStep keeps a reference to script for its lifetime or until this function
     /// is called again.
-    pub fn setLinkerScriptContents(self: &LibOrExeStep, script: []const u8) {
+    pub fn setLinkerScriptContents(self: &LibExeObjStep, script: []const u8) {
         self.linker_script = LinkerScript.Embed { script };
     }
 
-    pub fn setLinkerScriptPath(self: &LibOrExeStep, path: []const u8) {
+    pub fn setLinkerScriptPath(self: &LibExeObjStep, path: []const u8) {
         self.linker_script = LinkerScript.Path { path };
     }
 
-    pub fn linkSystemLibrary(self: &LibOrExeStep, name: []const u8) {
+    pub fn linkSystemLibrary(self: &LibExeObjStep, name: []const u8) {
         %%self.link_libs.put(name);
     }
 
-    pub fn setVerbose(self: &LibOrExeStep, value: bool) {
-        self.verbose = value;
-    }
-
-    pub fn setRelease(self: &LibOrExeStep, value: bool) {
-        self.release = value;
-    }
-
-    pub fn setOutputPath(self: &LibOrExeStep, value: []const u8) {
-        self.output_path = value;
-    }
-
-    fn make(step: &Step) -> %void {
-        const self = @fieldParentPtr(LibOrExeStep, "step", step);
-        const builder = self.builder;
-
-        var zig_args = List([]const u8).init(builder.allocator);
-        defer zig_args.deinit();
-
-        const cmd = switch (self.kind) {
-            Kind.Lib => "build_lib",
-            Kind.Exe => "build_exe",
-        };
-        %%zig_args.append(cmd);
-        %%zig_args.append(builder.pathFromRoot(self.root_src));
-
-        if (self.verbose) {
-            %%zig_args.append("--verbose");
-        }
-
-        if (self.release) {
-            %%zig_args.append("--release");
-        }
-
-        test (self.output_path) |output_path| {
-            %%zig_args.append("--output");
-            %%zig_args.append(builder.pathFromRoot(output_path));
-        }
-
-        %%zig_args.append("--name");
-        %%zig_args.append(self.name);
-
-        if (self.kind == Kind.Lib and !self.static) {
-            %%zig_args.append("--ver-major");
-            %%zig_args.append(builder.fmt("{}", self.version.major));
-
-            %%zig_args.append("--ver-minor");
-            %%zig_args.append(builder.fmt("{}", self.version.minor));
-
-            %%zig_args.append("--ver-patch");
-            %%zig_args.append(builder.fmt("{}", self.version.patch));
-        }
-
-        switch (self.target) {
-            Target.Native => {},
-            Target.Cross => |cross_target| {
-                %%zig_args.append("--target-arch");
-                %%zig_args.append(@enumTagName(cross_target.arch));
-
-                %%zig_args.append("--target-os");
-                %%zig_args.append(@enumTagName(cross_target.os));
-
-                %%zig_args.append("--target-environ");
-                %%zig_args.append(@enumTagName(cross_target.environ));
-            },
-        }
-
-        switch (self.linker_script) {
-            LinkerScript.None => {},
-            LinkerScript.Embed => |script| {
-                const tmp_file_name = "linker.ld.tmp"; // TODO issue #298
-                io.writeFile(tmp_file_name, script, builder.allocator)
-                    %% |err| debug.panic("unable to write linker script: {}\n", @errorName(err));
-                %%zig_args.append("--linker-script");
-                %%zig_args.append(tmp_file_name);
-            },
-            LinkerScript.Path => |path| {
-                %%zig_args.append("--linker-script");
-                %%zig_args.append(path);
-            },
-        }
-
-        {
-            var it = self.link_libs.iterator();
-            while (true) {
-                const entry = it.next() ?? break;
-                %%zig_args.append("--library");
-                %%zig_args.append(entry.key);
-            }
-        }
-
-        for (builder.include_paths.toSliceConst()) |include_path| {
-            %%zig_args.append("-isystem");
-            %%zig_args.append(include_path);
-        }
-
-        for (builder.rpaths.toSliceConst()) |rpath| {
-            %%zig_args.append("-rpath");
-            %%zig_args.append(rpath);
-        }
-
-        for (builder.lib_paths.toSliceConst()) |lib_path| {
-            %%zig_args.append("--library-path");
-            %%zig_args.append(lib_path);
-        }
-
-        %%builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
-
-        if (self.kind == Kind.Lib and !self.static) {
-            // sym link for libfoo.so.1 to libfoo.so.1.2.3
-            %%os.atomicSymLink(builder.allocator, self.out_filename, self.out_filename_major_only);
-            // sym link for libfoo.so to libfoo.so.1
-            %%os.atomicSymLink(builder.allocator, self.out_filename_major_only, self.out_filename_name_only);
-        }
-    }
-};
-
-pub const ObjectStep = struct {
-    step: Step,
-    builder: &Builder,
-    root_src: []const u8,
-    name: []const u8,
-    target: Target,
-    verbose: bool,
-    release: bool,
-    output_path: ?[]const u8,
-
-    pub fn init(builder: &Builder, name: []const u8, root_src: []const u8) -> ObjectStep {
-        ObjectStep {
-            .builder = builder,
-            .verbose = false,
-            .release = false,
-            .root_src = root_src,
-            .name = name,
-            .target = Target.Native,
-            .step = Step.init(name, builder.allocator, make),
-            .output_path = null,
-        }
-    }
-
-    pub fn setTarget(self: &ObjectStep, target_arch: Arch, target_os: Os, target_environ: Environ) {
-        self.target = Target.Cross {
-            CrossTarget {
-                .arch = target_arch,
-                .os = target_os,
-                .environ = target_environ,
-            }
-        };
-    }
-
-    pub fn setVerbose(self: &ObjectStep, value: bool) {
-        self.verbose = value;
-    }
-
-    pub fn setRelease(self: &ObjectStep, value: bool) {
-        self.release = value;
-    }
-
-    pub fn setOutputPath(self: &ObjectStep, value: []const u8) {
-        self.output_path = value;
-    }
-
-    fn make(step: &Step) -> %void {
-        const self = @fieldParentPtr(ObjectStep, "step", step);
-        const builder = self.builder;
-
-        var zig_args = List([]const u8).init(builder.allocator);
-        defer zig_args.deinit();
-
-        %%zig_args.append("build_obj");
-        %%zig_args.append(builder.pathFromRoot(self.root_src));
-
-        if (self.verbose) {
-            %%zig_args.append("--verbose");
-        }
-
-        if (self.release) {
-            %%zig_args.append("--release");
-        }
-
-        test (self.output_path) |output_path| {
-            %%zig_args.append("--output");
-            %%zig_args.append(builder.pathFromRoot(output_path));
-        }
-
-        %%zig_args.append("--name");
-        %%zig_args.append(self.name);
-
-        switch (self.target) {
-            Target.Native => {},
-            Target.Cross => |cross_target| {
-                %%zig_args.append("--target-arch");
-                %%zig_args.append(@enumTagName(cross_target.arch));
-
-                %%zig_args.append("--target-os");
-                %%zig_args.append(@enumTagName(cross_target.os));
-
-                %%zig_args.append("--target-environ");
-                %%zig_args.append(@enumTagName(cross_target.environ));
-            },
-        }
-
-        for (builder.include_paths.toSliceConst()) |include_path| {
-            %%zig_args.append("-isystem");
-            %%zig_args.append(include_path);
-        }
-
-        for (builder.rpaths.toSliceConst()) |rpath| {
-            %%zig_args.append("-rpath");
-            %%zig_args.append(rpath);
-        }
-
-        for (builder.lib_paths.toSliceConst()) |lib_path| {
-            %%zig_args.append("--library-path");
-            %%zig_args.append(lib_path);
-        }
-
-        %%builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
-    }
-};
-
-pub const AsmStep = struct {
-    step: Step,
-    builder: &Builder,
-    name: []const u8,
-    target: Target,
-    verbose: bool,
-    release: bool,
-    output_path: ?[]const u8,
-    src_path: []const u8,
-
-    pub fn init(builder: &Builder, name: []const u8, src_path: []const u8) -> AsmStep {
-        var self = AsmStep {
-            .step = Step.init(name, builder.allocator, make),
-            .builder = builder,
-            .name = name,
-            .target = Target.Native,
-            .verbose = false,
-            .release = false,
-            .output_path = null,
-            .src_path = src_path,
-        };
-        return self;
-    }
-
-    pub fn setTarget(self: &AsmStep, target_arch: Arch, target_os: Os, target_environ: Environ) {
-        self.target = Target.Cross {
-            CrossTarget {
-                .arch = target_arch,
-                .os = target_os,
-                .environ = target_environ,
-            }
-        };
-    }
-
-    pub fn setVerbose(self: &AsmStep, value: bool) {
+    pub fn setVerbose(self: &LibExeObjStep, value: bool) {
         self.verbose = value;
     }
 
-    pub fn setRelease(self: &AsmStep, value: bool) {
+    pub fn setRelease(self: &LibExeObjStep, value: bool) {
         self.release = value;
     }
 
-    pub fn setOutputPath(self: &AsmStep, value: []const u8) {
+    pub fn setOutputPath(self: &LibExeObjStep, value: []const u8) {
         self.output_path = value;
     }
 
-    fn make(step: &Step) -> %void {
-        const self = @fieldParentPtr(AsmStep, "step", step);
-        const builder = self.builder;
-
-        var zig_args = List([]const u8).init(builder.allocator);
-        defer zig_args.deinit();
-
-        %%zig_args.append("asm");
-        %%zig_args.append(builder.pathFromRoot(self.src_path));
-
-        if (self.verbose) {
-            %%zig_args.append("--verbose");
-        }
-
-        if (self.release) {
-            %%zig_args.append("--release");
-        }
-
-        test (self.output_path) |output_path| {
-            %%zig_args.append("--output");
-            %%zig_args.append(builder.pathFromRoot(output_path));
-        }
-
-        %%zig_args.append("--name");
-        %%zig_args.append(self.name);
-
-        switch (self.target) {
-            Target.Native => {},
-            Target.Cross => |cross_target| {
-                %%zig_args.append("--target-arch");
-                %%zig_args.append(@enumTagName(cross_target.arch));
-
-                %%zig_args.append("--target-os");
-                %%zig_args.append(@enumTagName(cross_target.os));
-
-                %%zig_args.append("--target-environ");
-                %%zig_args.append(@enumTagName(cross_target.environ));
-            },
-        }
-
-        %%builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
+    pub fn addAssemblyFile(self: &LibExeObjStep, path: []const u8) {
+        %%self.assembly_files.append(path);
     }
-};
 
-pub const LinkStep = struct {
-    step: Step,
-    builder: &Builder,
-    name: []const u8,
-    target: Target,
-    linker_script: LinkerScript,
-    link_libs: BufSet,
-    verbose: bool,
-    release: bool,
-    output_path: ?[]const u8,
-    object_files: List([]const u8),
-    static: bool,
-    out_filename: []const u8,
-    out_type: OutType,
-    version: Version,
-    major_only_filename: []const u8,
-    name_only_filename: []const u8,
-
-    const OutType = enum {
-        Exe,
-        Lib,
-    };
+    pub fn addObjectFile(self: &LibExeObjStep, path: []const u8) {
+        assert(self.kind != Kind.Obj);
 
-    pub fn initExecutable(builder: &Builder, name: []const u8) -> LinkStep {
-        return init(builder, name, OutType.Exe, builder.version(0, 0, 0), false)
+        %%self.object_files.append(path);
     }
 
-    pub fn initSharedLibrary(builder: &Builder, name: []const u8, version: &const Version) -> LinkStep {
-        return init(builder, name, OutType.Lib, version, false)
-    }
+    pub fn addObject(self: &LibExeObjStep, obj: &LibExeObjStep) {
+        assert(obj.kind == Kind.Obj);
+        assert(self.kind != Kind.Obj);
 
-    pub fn initStaticLibrary(builder: &Builder, name: []const u8) -> LinkStep {
-        return init(builder, name, OutType.Lib, builder.version(0, 0, 0), true)
-    }
-
-    fn init(builder: &Builder, name: []const u8, out_type: OutType, version: &const Version, static: bool) -> LinkStep {
-        var self = LinkStep {
-            .builder = builder,
-            .verbose = false,
-            .release = false,
-            .name = name,
-            .target = Target.Native,
-            .linker_script = LinkerScript.None,
-            .link_libs = BufSet.init(builder.allocator),
-            .step = Step.init(name, builder.allocator, make),
-            .output_path = null,
-            .object_files = List([]const u8).init(builder.allocator),
-            .out_type = out_type,
-            .version = *version,
-            .static = static,
-            .out_filename = undefined,
-            .major_only_filename = undefined,
-            .name_only_filename = undefined,
-        };
-        self.computeOutFileName();
-        return self;
-    }
-
-    fn computeOutFileName(self: &LinkStep) {
-        switch (self.out_type) {
-            OutType.Exe => {
-                self.out_filename = self.builder.fmt("{}{}", self.name, self.target.exeFileExt());
-            },
-            OutType.Lib => {
-                if (self.static) {
-                    self.out_filename = self.builder.fmt("lib{}.a", self.name);
-                } else {
-                    self.out_filename = self.builder.fmt("lib{}.so.{d}.{d}.{d}",
-                        self.name, self.version.major, self.version.minor, self.version.patch);
-                    self.major_only_filename = self.builder.fmt("lib{}.so.{d}", self.name, self.version.major);
-                    self.name_only_filename = self.builder.fmt("lib{}.so", self.name);
-                }
-            },
-        }
-    }
-
-    pub fn addObjectFile(self: &LinkStep, file: []const u8) {
-        %%self.object_files.append(file);
-    }
-
-    pub fn addObject(self: &LinkStep, obj: &ObjectStep) {
         self.step.dependOn(&obj.step);
 
         const path_to_obj = test (obj.output_path) |explicit_out_path| {
@@ -1143,61 +774,11 @@ pub const LinkStep = struct {
         %%self.object_files.append(path_to_obj);
     }
 
-    pub fn addAssembly(self: &LinkStep, assembly: &AsmStep) {
-        self.step.dependOn(&assembly.step);
-
-        const path_to_obj = test (assembly.output_path) |explicit_out_path| {
-            explicit_out_path
-        } else {
-            // TODO make it so we always know where this will be
-            %%os.path.join(self.builder.allocator, self.builder.out_dir,
-                self.builder.fmt("{}{}", assembly.name, assembly.target.oFileExt()))
-        };
-        %%self.object_files.append(path_to_obj);
-    }
-
-    pub fn setTarget(self: &LinkStep, target_arch: Arch, target_os: Os, target_environ: Environ) {
-        self.target = Target.Cross {
-            CrossTarget {
-                .arch = target_arch,
-                .os = target_os,
-                .environ = target_environ,
-            }
-        };
-        self.computeOutFileName();
-    }
-
-    /// LinkStep keeps a reference to script for its lifetime or until this function
-    /// is called again.
-    pub fn setLinkerScriptContents(self: &LinkStep, script: []const u8) {
-        self.linker_script = LinkerScript.Embed { script };
-    }
-
-    pub fn setLinkerScriptPath(self: &LinkStep, path: []const u8) {
-        self.linker_script = LinkerScript.Path { path };
-    }
-
-    pub fn linkSystemLibrary(self: &LinkStep, name: []const u8) {
-        %%self.link_libs.put(name);
-    }
-
-    pub fn setVerbose(self: &LinkStep, value: bool) {
-        self.verbose = value;
-    }
-
-    pub fn setRelease(self: &LinkStep, value: bool) {
-        self.release = value;
-    }
-
-    pub fn setOutputPath(self: &LinkStep, value: []const u8) {
-        self.output_path = value;
-    }
-
     fn make(step: &Step) -> %void {
-        const self = @fieldParentPtr(LinkStep, "step", step);
+        const self = @fieldParentPtr(LibExeObjStep, "step", step);
         const builder = self.builder;
 
-        if (self.object_files.len == 0) {
+        if (self.root_src == null and self.object_files.len == 0 and self.assembly_files.len == 0) {
             %%io.stderr.printf("{}: linker needs 1 or more objects to link\n", step.name);
             return error.NeedAnObject;
         }
@@ -1205,16 +786,27 @@ pub const LinkStep = struct {
         var zig_args = List([]const u8).init(builder.allocator);
         defer zig_args.deinit();
 
-        const cmd = switch (self.out_type) {
-            OutType.Exe => "link_exe",
-            OutType.Lib => "link_lib",
+        const cmd = switch (self.kind) {
+            Kind.Lib => "build_lib",
+            Kind.Exe => "build_exe",
+            Kind.Obj => "build_obj",
         };
         %%zig_args.append(cmd);
 
+        test (self.root_src) |root_src| {
+            %%zig_args.append(builder.pathFromRoot(root_src));
+        }
+
         for (self.object_files.toSliceConst()) |object_file| {
+            %%zig_args.append("--object");
             %%zig_args.append(builder.pathFromRoot(object_file));
         }
 
+        for (self.assembly_files.toSliceConst()) |asm_file| {
+            %%zig_args.append("--assembly");
+            %%zig_args.append(builder.pathFromRoot(asm_file));
+        }
+
         if (self.verbose) {
             %%zig_args.append("--verbose");
         }
@@ -1223,10 +815,6 @@ pub const LinkStep = struct {
             %%zig_args.append("--release");
         }
 
-        if (self.static) {
-            %%zig_args.append("--static");
-        }
-
         test (self.output_path) |output_path| {
             %%zig_args.append("--output");
             %%zig_args.append(builder.pathFromRoot(output_path));
@@ -1235,6 +823,17 @@ pub const LinkStep = struct {
         %%zig_args.append("--name");
         %%zig_args.append(self.name);
 
+        if (self.kind == Kind.Lib and !self.static) {
+            %%zig_args.append("--ver-major");
+            %%zig_args.append(builder.fmt("{}", self.version.major));
+
+            %%zig_args.append("--ver-minor");
+            %%zig_args.append(builder.fmt("{}", self.version.minor));
+
+            %%zig_args.append("--ver-patch");
+            %%zig_args.append(builder.fmt("{}", self.version.patch));
+        }
+
         switch (self.target) {
             Target.Native => {},
             Target.Cross => |cross_target| {
@@ -1273,6 +872,11 @@ pub const LinkStep = struct {
             }
         }
 
+        for (builder.include_paths.toSliceConst()) |include_path| {
+            %%zig_args.append("-isystem");
+            %%zig_args.append(include_path);
+        }
+
         for (builder.rpaths.toSliceConst()) |rpath| {
             %%zig_args.append("-rpath");
             %%zig_args.append(rpath);
@@ -1284,6 +888,13 @@ pub const LinkStep = struct {
         }
 
         %%builder.spawnChild(builder.zig_exe, zig_args.toSliceConst());
+
+        if (self.kind == Kind.Lib and !self.static) {
+            // sym link for libfoo.so.1 to libfoo.so.1.2.3
+            %%os.atomicSymLink(builder.allocator, self.out_filename, self.out_filename_major_only);
+            // sym link for libfoo.so to libfoo.so.1
+            %%os.atomicSymLink(builder.allocator, self.out_filename_major_only, self.out_filename_name_only);
+        }
     }
 };
 
@@ -1592,15 +1203,17 @@ pub const CExecutable = struct {
         %%self.full_path_libs.append(clib.out_filename);
     }
 
-    pub fn linkLibrary(self: &CExecutable, lib: &LibOrExeStep) {
-        assert(lib.kind == LibOrExeStep.Kind.Lib);
+    pub fn linkLibrary(self: &CExecutable, lib: &LibExeObjStep) {
+        assert(lib.kind == LibExeObjStep.Kind.Lib);
         self.step.dependOn(&lib.step);
         %%self.full_path_libs.append(lib.out_filename);
         // TODO should be some kind of isolated directory that only has this header in it
         %%self.include_dirs.append(self.builder.out_dir);
     }
 
-    pub fn addObject(self: &CExecutable, obj: &ObjectStep) {
+    pub fn addObject(self: &CExecutable, obj: &LibExeObjStep) {
+        assert(obj.kind == LibExeObjStep.Kind.Obj);
+
         self.step.dependOn(&obj.step);
 
         // TODO make it so we always know where this will be
std/debug.zig
@@ -90,7 +90,11 @@ pub fn writeStackTrace(out_stream: &io.OutStream, allocator: &mem.Allocator, tty
                 // at compile time. I'll call it issue #313
                 const ptr_hex = if (@sizeOf(usize) == 4) "0x{x8}" else "0x{x16}";
 
-                const compile_unit = findCompileUnit(st, return_address) ?? return error.MissingDebugInfo;
+                const compile_unit = findCompileUnit(st, return_address) ?? {
+                    %return out_stream.print(DIM ++ ptr_hex ++ " in ??? (???)" ++ RESET ++ "\n\n\n", return_address);
+                    %return out_stream.flush();
+                    continue;
+                };
                 const compile_unit_name = %return compile_unit.die.getAttrString(st, DW.AT_name);
                 try (getLineNumberInfo(st, compile_unit, usize(return_address) - 1)) |line_info| {
                     defer line_info.deinit();
test/cases/cast.zig
@@ -150,3 +150,12 @@ fn peerTypeEmptyArrayAndSlice(a: bool, slice: []const u8) -> []const u8 {
 
     return slice[0...1];
 }
+
+test "implicitly cast from [N]T to ?[]const T" {
+    assert(mem.eql(u8, ??castToMaybeSlice(), "hi"));
+    comptime assert(mem.eql(u8, ??castToMaybeSlice(), "hi"));
+}
+
+fn castToMaybeSlice() -> ?[]const u8 {
+    return "hi";
+}
test/tests.zig
@@ -355,18 +355,16 @@ pub const CompareOutputContext = struct {
                         return;
                 }
 
-                const assembly = b.addAssemble("test", root_src);
+                const exe = b.addExecutable("test", null);
+                exe.addAssemblyFile(root_src);
+                exe.setOutputPath(exe_path);
 
                 for (case.sources.toSliceConst()) |src_file| {
                     const expanded_src_path = %%os.path.join(b.allocator, "test_artifacts", src_file.filename);
                     const write_src = b.addWriteFile(expanded_src_path, src_file.source);
-                    assembly.step.dependOn(&write_src.step);
+                    exe.step.dependOn(&write_src.step);
                 }
 
-                const exe = b.addLinkExecutable("test");
-                exe.addAssembly(assembly);
-                exe.setOutputPath(exe_path);
-
                 const run_and_cmp_output = RunCompareOutputStep.create(self, exe_path, annotated_case_name,
                     case.expected_output);
                 run_and_cmp_output.step.dependOn(&exe.step);