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

[Ian Anderson via Phabricator via cfe-commits]

iana added inline comments.


================
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
+}
----------------
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.


Repository:
  rG LLVM Github Monorepo

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

https://reviews.llvm.org/D157793