Commit 01698528d1

@@ -19964,6 +19964,14 @@ fn analyzeSlice(
                 slice_ty = ptr_ptr_child_ty;
                 array_ty = ptr_ptr_child_ty;
                 elem_ty = ptr_ptr_child_ty.childType();
+
+                if (ptr_ptr_child_ty.ptrSize() == .C) {
+                    if (try sema.resolveDefinedValue(block, ptr_src, ptr_or_slice)) |ptr_val| {
+                        if (ptr_val.isNull()) {
+                            return sema.fail(block, ptr_src, "slice of null pointer", .{});
+                        }
+                    }
+                }
             },
             .Slice => {
                 ptr_sentinel = ptr_ptr_child_ty.sentinel();
@@ -20162,6 +20170,12 @@ fn analyzeSlice(
 
     try sema.requireRuntimeBlock(block, src);
     if (block.wantSafety()) {
+        // requirement: slicing C ptr is non-null
+        if (ptr_ptr_child_ty.isCPtr()) {
+            const is_non_null = try sema.analyzeIsNull(block, ptr_src, ptr, true);
+            try sema.addSafetyCheck(block, is_non_null, .unwrap_null);
+        }
+
         // requirement: end <= len
         const opt_len_inst = if (array_ty.zigTypeTag() == .Array)
             try sema.addIntUnsigned(Type.usize, array_ty.arrayLenIncludingSentinel())

@@ -233,6 +233,7 @@ fn sliceFromLenToLen(a_slice: []u8, start: usize, end: usize) []u8 {
 
 test "C pointer" {
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
 
     var buf: [*c]const u8 = "kjdhfkjdhfdkjhfkfjhdfkjdhfkdjhfdkjhf";
     var len: u32 = 10;

@@ -0,0 +1,10 @@
+comptime {
+    var x: [*c]u8 = null;
+    var runtime_len: usize = 0;
+    var y = x[0..runtime_len];
+    _ = y;
+}
+
+// slice of null C pointer
+//
+// :4:14: error: slice of null pointer