Before this patch, running
#define TEST(T) T
#define PARALLEL(X) TEST(X)
PARALLEL(
for (int i = 0; i < N; i++) { \
_Pragma("omp ordered") \
S[0] += C[i] + D[i]; \
})
through 'gcc -E' yielded
#pragma omp ordered
for (int i = 0; i < N; i++) { S[0] += C[i] + D[i]; }
Note that the '#pragma omp ordered' is now above the loop, i.e. before
all macro arguments (and macro expansions).
With the patch, the result is the following, which matches Clang and I
assume GCC before 4.2 or 4.3, but I have no GCC 4.x available:
for (int i = 0; i < N; i++) {
#pragma omp ordered
S[0] += C[i] + D[i]; }
The reason seems to be the addition done for PR34692 in r131819, which
added code to avoid an ICE with
FOO(
#pragma GCC diagnostic
)
There is a length description in macro.c about what it does and the
pragma_buff which is passed around, including to the now modified
collect_args. Namely, the comment above enter_macro_context states:
If there were additionally any unexpanded deferred #pragma
directives among macro arguments, push another context containing
the pragma tokens before the yet-to-be-rescanned replacement list
and return two.
While that seems to work fine with #pragma, it obviously does not do
what it should for _Pragma. The solution in the patch was to add a
flag to distinguish the CPP_PRAGMA coming from the _Pragma operator
(alias BT_PRAGMA) from the CPP_PRAGMA coming from a user's #pragma.
OK for mainline? – It is a long-standing regression, but it hasn't
been reported for a while. Thus: how do you feel about backporting?
I did test it with a full bootstrap + regtesting. I also tested
omptests (cf. PR).
Tobias
PS: I had the hope that it would fix some of the other _Pragma related
PRs (see e.g. refs in this PR102409 or search Bugzilla), but it does
not seem to help for those. I do note that most of them are related to
diagnostic. In particular, for PR91669, the output of gcc -E is the
same for GCC 10, for a patched GCC and for clang-11, which makes the
result (issue unaffected by this patch) not that surprising.
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libcpp: Fix _Pragma expansion [PR102409]
Both #pragma and _Pragma ended up as CPP_PRAGMA. Presumably since
r131819 (2008, GCC 4.3) for PR34692, pragmas are not expanded in
macro arguments but are output as is before. From the old bug report,
that was to fix usage like
FOO (
#pragma GCC diagnostic
)
However, that change also affected _Pragma such that
BAR (
"1";
_Pragma("omp ..."); )
yielded
#pragma omp ...
followed by what BAR expanded too, possibly including '"1";'.
This commit adds a flag, PRAGMA_OP, to tokens to make the two
distinguishable - and include again _Pragma in the expanded arguments.
libcpp/ChangeLog:
PR c++/102409
* directives.c (destringize_and_run): Add PRAGMA_OP to the
CPP_PRAGMA token's flags to mark is as coming from _Pragma.
* include/cpplib.h (PRAGMA_OP): #define, to be used with token flags.
* macro.c (collect_args): Only handle CPP_PRAGMA special if PRAGMA_OP
is set.
libcpp/directives.c | 2 ++
libcpp/include/cpplib.h | 1 +
libcpp/macro.c | 2 +-
3 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/libcpp/directives.c b/libcpp/directives.c
index b4bc8b4df30..34f7677f718 100644
--- a/libcpp/directives.c
+++ b/libcpp/directives.c
@@ -1907,6 +1907,8 @@ destringize_and_run (cpp_reader *pfile, const cpp_string *in,
save_directive = pfile->directive;
pfile->directive = &dtable[T_PRAGMA];
do_pragma (pfile);
+ if (pfile->directive_result.type == CPP_PRAGMA)
+ pfile->directive_result.flags |= PRAGMA_OP;
end_directive (pfile, 1);
pfile->directive = save_directive;
diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index 6e2fcb6b1f2..56b07acc1d7 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -198,6 +198,7 @@ struct GTY(()) cpp_string {
operator, or before this token
after a # operator. */
#define NO_EXPAND (1 << 10) /* Do not macro-expand this token. */
+#define PRAGMA_OP (1 << 11) /* _Pragma token. */
/* Specify which field, if any, of the cpp_token union is used. */
diff --git a/libcpp/macro.c b/libcpp/macro.c
index f214548de1e..b2f797cae35 100644
--- a/libcpp/macro.c
+++ b/libcpp/macro.c
@@ -1259,7 +1259,7 @@ collect_args (cpp_reader *pfile, const cpp_hashnode *node,
else if (token->type == CPP_EOF
|| (token->type == CPP_HASH && token->flags & BOL))
break;
- else if (token->type == CPP_PRAGMA)
+ else if (token->type == CPP_PRAGMA && !(token->flags & PRAGMA_OP))
{
cpp_token *newtok = _cpp_temp_token (pfile);
