[cfe-commits] [patch] Elided __VA_ARGS__ now erase preceding comma in MS mode

[Aaron Ballman]

On Mon, Aug 27, 2012 at 5:42 AM, Martin Vejnár <Martin.Vejnar at avg.com> wrote:
> I’ve beed asked to post this patch to cfe-commits, so there you go. The
> preprocessor show now consume a comma before elided __VA_ARGS__ even if
> there is no pasting operator in between. E.g.

In the future, can you submit as an svn patch since not everyone uses git?

> +    if (PP.getLangOpts().MicrosoftMode &&
> +        (unsigned)ArgNo == Macro->getNumArgs()-1 && // is __VA_ARGS__
> +        ActualArgs->isVarargsElidedUse() &&       // Argument elided.
> +        !ResultToks.empty() && ResultToks.back().is(tok::comma)) {
> +      // Never add a space, even if the comma or arg had a space.
> +      NextTokGetsSpace = false;
> +
> +      // Remove the comma
> +      ResultToks.pop_back();
> +
> +      // If the comma was right after another paste (e.g. "X##,__VA_ARGS__"),
> +      // the paste is ignored by MS compilers.

Minor nit: the comment doesn't seem to match the code.  You've checked
for a comma then a hash, but the comment implies you've found a hash
and then a comma.

> +      if (!ResultToks.empty() && ResultToks.back().is(tok::hashhash))
> +        ResultToks.pop_back();
> +      continue;
> +    }
> +

>
> --- /dev/null
> +++ b/test/Preprocessor/macro_fn_ms_comma_swallow.c
> @@ -0,0 +1,7 @@
> +// Test the GNU comma swallowing extension.
> +// RUN: %clang_cc1 %s -E -fms-compatibility | FileCheck -strict-whitespace %s
> +
> +// should eat the comma before emtpy varargs
> +// CHECK: 1: {foo}
> +#define X1(b, ...) {b,__VA_ARGS__}
> +1: X1(foo)

Instead of creating an entire test case for this, it might make more
sense to put this test macro_fn_comma_swallow.c and add a second pass
to the test using a check prefix for MS.

Otherwise, everything looks good!  Thanks for the patch!

~Aaron