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libcpp: Fix error recovery after use of __VA_ARGS__ as macro argument [PR118674]

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The following testcase ICEs after emitting one pedwarn (about using
__VA_ARGS__ in a place where it shouldn't be used) and one error.
The error is emitted by _cpp_save_parameter where it sees the node
has been used already earlier.  But unlike the other _cpp_save_parameter
caller which does goto out; if it returns false, this call with explicit
__VA_ARGS__ doesn't and if it increments number of parameters etc. after
the error, we then try to unsave it twice.

The following patch fixes it by doing the goto out in that case too,
the macro will then not be considered as variable arguments macro,
but for error recovery I think that is fine.
The other option would be before the other _cpp_save_parameter caller
check if the node is pfile->spec_nodes.n__VA_ARGS__ and in that case
also error and goto out, but that seems more expensive than this for
the common case that the macro definition is correct.

2025-04-09  Jakub Jelinek  <jakub@redhat.com>

	PR preprocessor/118674
	* macro.cc (parse_params) <case CPP_ELLIPSIS>: If _cpp_save_parameter
	failed for __VA_ARGS__, goto out.

	* gcc.dg/cpp/pr118674.c: New test.
This commit is contained in:
Jakub Jelinek 2025-04-09 12:27:38 +02:00 • committed by Jakub Jelinek
parent ac1044da4b
commit 6e77a83ffb
2 changed files with 9 additions and 3 deletions
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5
gcc/testsuite/gcc.dg/cpp/pr118674.c Normal file
View file

@ -0,0 +1,5 @@
/* PR preprocessor/118674 */
/* { dg-do preprocess } */
#define M(__VA_ARGS__, ...)
/* { dg-error "'__VA_ARGS__' can only appear in the expansion of a C99 variadic macro" "" { target *-*-* } .-1 } */
/* { dg-error "duplicate macro parameter '__VA_ARGS__'" "" { target *-*-* } .-2 } */

7
libcpp/macro.cc
View file

@ -3610,9 +3610,10 @@ parse_params (cpp_reader *pfile, unsigned *n_ptr, bool *variadic_ptr)
if (!prev_ident)
{
/* An ISO bare ellipsis. */
_cpp_save_parameter (pfile, nparms,
pfile->spec_nodes.n__VA_ARGS__,
pfile->spec_nodes.n__VA_ARGS__);
if (!_cpp_save_parameter (pfile, nparms,
pfile->spec_nodes.n__VA_ARGS__,
pfile->spec_nodes.n__VA_ARGS__))
goto out;
nparms++;
pfile->state.va_args_ok = 1;
if (! CPP_OPTION (pfile, c99)