Commit 76c62e509b

Brandon Black <bblack@wikimedia.org>
2025-09-02 19:20:11
Fix cmsghdr struct for the *nixes
Previously we had a single definition of std.c.cmsghdr for all libc-linking platforms which aliased from the Solaris definition, a superfluous matching one in std.os.dragonfly, and no others. The existing definition from std.c didn't actually work for Linux, as Linux's "len" field is usize in the kernel's definition. Emscripten follows the Linux model of course (but uses the binary-compatible musl definition, which has an endian-sensitive padding scheme to make the len type "socklen_t" even though the kernel uses a usize, which is fair). This unifies and documents all the known *nix-ish cases (I'm not sure if wasi or windows really has cmsghdr support? Could be added later, void for now), such that c.cmsghdr and posix.system.cmsghdr should work correctly for all the known cases here, libc or otherwise.
master
1 parent b1189ab
Changed files (4)
lib
std
c
dragonfly.zig
solaris.zig
os
linux.zig
c.zig
lib/std/c/dragonfly.zig
@@ -158,12 +158,6 @@ pub const BADSIG = SIG.ERR;
 
 pub const sig_t = *const fn (i32) callconv(.c) void;
 
-pub const cmsghdr = extern struct {
-    len: socklen_t,
-    level: c_int,
-    type: c_int,
-};
-
 pub const cmsgcred = extern struct {
     pid: pid_t,
     uid: uid_t,
lib/std/c/solaris.zig
@@ -31,12 +31,6 @@ pub const poolid_t = id_t;
 pub const zoneid_t = id_t;
 pub const ctid_t = id_t;
 
-pub const cmsghdr = extern struct {
-    len: socklen_t,
-    level: i32,
-    type: i32,
-};
-
 pub const SCM = struct {
     pub const UCRED = 0x1012;
     pub const RIGHTS = 0x1010;
lib/std/os/linux.zig
@@ -9709,6 +9709,13 @@ pub const msghdr_const = extern struct {
     flags: u32,
 };
 
+// https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/socket.h?id=b320789d6883cc00ac78ce83bccbfe7ed58afcf0#n105
+pub const cmsghdr = extern struct {
+    len: usize,
+    level: i32,
+    type: i32,
+};
+
 /// The syscalls, but with Zig error sets, going through libc if linking libc,
 /// and with some footguns eliminated.
 pub const wrapped = struct {
lib/std/c.zig
@@ -4171,6 +4171,39 @@ pub const msghdr_const = switch (native_os) {
     },
     else => void,
 };
+pub const cmsghdr = switch (native_os) {
+    // https://github.com/emscripten-core/emscripten/blob/96371ed7888fc78c040179f4d4faa82a6a07a116/system/lib/libc/musl/include/sys/socket.h#L44
+    .linux, .emscripten => linux.cmsghdr,
+    // https://github.com/freebsd/freebsd-src/blob/b197d2abcb6895d78bc9df8404e374397aa44748/sys/sys/socket.h#L492
+    .freebsd,
+    // https://github.com/DragonFlyBSD/DragonFlyBSD/blob/107c0518337ba90e7fa49e74845d8d44320c9a6d/sys/sys/socket.h#L452
+    .dragonfly,
+    // https://github.com/NetBSD/src/blob/ba8e1774fd9c0c26ecca461c07bc95d9ebb69579/sys/sys/socket.h#L528
+    .netbsd,
+    // https://github.com/openbsd/src/blob/master/sys/sys/socket.h#L527
+    .openbsd,
+    // https://github.com/kofemann/opensolaris/blob/80192cd83bf665e708269dae856f9145f7190f74/usr/src/uts/common/sys/socket.h#L416
+    .solaris,
+    // https://github.com/illumos/illumos-gate/blob/afdf2e523873cb523df379676067bf9785a0f456/usr/src/uts/common/sys/socket.h#L460
+    .illumos,
+    // https://github.com/SerenityOS/serenity/blob/4ee360a348a5e2490eeaeeabb3eb19e70dd450eb/Kernel/API/POSIX/sys/socket.h#L68
+    .serenity,
+    // https://github.com/haiku/haiku/blob/b54f586058fd6623645512e4631468cede9933b9/headers/posix/sys/socket.h#L132
+    .haiku,
+    // https://github.com/apple/darwin-xnu/blob/2ff845c2e033bd0ff64b5b6aa6063a1f8f65aa32/bsd/sys/socket.h#L1041
+    .macos,
+    .driverkit,
+    .ios,
+    .tvos,
+    .visionos,
+    .watchos,
+    => extern struct {
+        len: socklen_t,
+        level: c_int,
+        type: c_int,
+    },
+    else => void,
+};
 pub const nfds_t = switch (native_os) {
     .linux => linux.nfds_t,
     .emscripten => emscripten.nfds_t,
@@ -11010,7 +11043,6 @@ pub const SCM = solaris.SCM;
 pub const SETCONTEXT = solaris.SETCONTEXT;
 pub const SETUSTACK = solaris.GETUSTACK;
 pub const SFD = solaris.SFD;
-pub const cmsghdr = solaris.cmsghdr;
 pub const ctid_t = solaris.ctid_t;
 pub const file_obj = solaris.file_obj;
 pub const fpregset_t = solaris.fpregset_t;