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libcpp: Fix up ##__VA_OPT__ handling [PR89971] 

In the following testcase we incorrectly error about pasting / token
with padding token (which is a result of __VA_OPT__); instead we should
like e.g. for ##arg where arg is empty macro argument clear PASTE_LEFT
flag of the previous token if __VA_OPT__ doesn't add any real tokens
(which can happen either because the macro doesn't have any tokens
passed to ... (i.e. __VA_ARGS__ expands to empty) or when __VA_OPT__
doesn't have any tokens in between ()s).

2021-12-30  Jakub Jelinek  <jakub@redhat.com>

	PR preprocessor/89971
libcpp/
	* macro.c (replace_args): For ##__VA_OPT__, if __VA_OPT__ expands
	to no tokens at all, drop PASTE_LEFT flag from the previous token.
gcc/testsuite/
	* c-c++-common/cpp/va-opt-9.c: New test.

(cherry picked from commit 5545d1edcb)
This commit is contained in:
Jakub Jelinek 2021-12-30 22:23:58 +01:00
parent 5d96fb401e
commit 86b98701bf
2 changed files with 25 additions and 0 deletions
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20
gcc/testsuite/c-c++-common/cpp/va-opt-9.c Normal file
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@ -0,0 +1,20 @@
/* PR preprocessor/89971 */
/* { dg-do compile } */
/* { dg-options "-std=gnu99" { target c } } */
/* { dg-options "-std=c++2a" { target c++ } } */
int a, c;
#define m1(...) a /##__VA_OPT__(b) c
#define m2(...) a /##__VA_OPT__() c
#define m3(...) a##__VA_OPT__()##b = 1
#define m4(...) a##__VA_OPT__(b c d)##e = 2
int
foo (void)
{
int d = m1();
int e = m2(1);
int m3(1 2 3);
int m4();
return d + e + ab + ae;
}

5
libcpp/macro.c
View File

@ -1886,6 +1886,11 @@ replace_args (cpp_reader *pfile, cpp_hashnode *node, cpp_macro *macro,
paste_flag = tokens_buff_last_token_ptr (buff);
}
if (start && paste_flag == start && (*start)->flags & PASTE_LEFT)
/* If __VA_OPT__ expands to nothing (either because __VA_ARGS__
is empty or because it is __VA_OPT__() ), drop PASTE_LEFT
flag from previous token. */
copy_paste_flag (pfile, start, &pfile->avoid_paste);
if (src->flags & PASTE_LEFT)
{
/* With a non-empty __VA_OPT__ on the LHS of ##, the last