[PATCH] D157793: [Headers] Add missing __need_ macros to stdarg.h

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman accepted this revision.
aaron.ballman added a comment.
This revision is now accepted and ready to land.

LGTM!



================
Comment at: clang/test/Headers/stdarg.c:34
+    __va_copy(g, v);
+    va_copy(g, v); // c89-error{{implicit}} c89-note{{va_copy}} c99-no-diagnostics
+}
----------------
iana wrote:
> aaron.ballman wrote:
> > You should spell out these diagnostics, and I think `c99-no-diagnostics` should be placed up by the RUN lines so it's more obvious that we expect no diagnostics in C99 mode.
> > 
> > Actually, this file should perhaps be split into two files as they're testing different things. (I was tripped up seeing no-diagnostics but we have `c99-error` entries above, that's when I realized the split file was being used differently in the RUN lines which is a bit novel.) But I'm not certain I fully understand what your comment means about why we're using split file in the first place, so I might be missing something.
> It's only trying to test what including <stdarg.h> gets you by default. The first chunk is to prove that nothing is provided via built-ins or anything like if you don't include anything. The second chunk shows that you get the expected declarations in each standard mode if you include <stdarg.h> with no `__need_` macros.
> 
> The problem is this.
> ```
> va_copy(g, v); // The first time you get: implicitly declaring library function 'va_copy'
> 
> va_copy(g, v); // But now the compiler has decided that va_copy has a declaration, so you don't get any diagnostics even though va_copy doesn't have its real declaration, I think the compiler assumes 'int va_copy(int, int)' or something like that.
> ```
> 
> Maybe we don't need to test the include-nothing case both here and stdargneeds.c?
> 
> D157757 has the same problem for `offsetof` but since it uses C23 also, the diagnostics get repeated.
Ah, I see now, thank you for the explanation.

The compiler adds an implicit function declaration for `va_copy` in C (so the signature is `int func()` as a K&R C function without a prototype), hence the need to split the file.

This seems reasonable to me.


Repository:
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https://reviews.llvm.org/D157793