https://gcc.gnu.org/ml/gcc-patches/2016-01/msg02243.html reported a regression introduced by r232893 (for PR preprocessor/69126) Minimal reproducer seems to be: $ cat /tmp/test.c # define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN \ _Pragma ("GCC diagnostic push") \ _Pragma ("GCC diagnostic ignored \"-Wuninitialized\"")\ _Pragma ("GCC diagnostic ignored \"-Wmaybe-uninitialized\"") # define YY_IGNORE_MAYBE_UNINITIALIZED_END \ _Pragma ("GCC diagnostic pop") void test (char yylval) { char *yyvsp; YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN *++yyvsp = yylval; YY_IGNORE_MAYBE_UNINITIALIZED_END } $ ./xgcc -B. -c /tmp/test.c -Wall /tmp/test.c: In function 'test': /tmp/test.c:12:12: warning: 'yyvsp' is used uninitialized in this function [-Wuninitialized] *++yyvsp = yylval; ~~~~~~~~~^~~~~~~~ $ ./xgcc -B. -c /tmp/test.c -save-temps $ ./xgcc -B. -c test.i -Wall (compiles with no warnings)
Breakpoint 4, linemap_compare_locations (set=0x7ffff7ff6000, pre=2147483641, post=post@entry=2147483656) at ../../src/libcpp/line-map.c:1326 (gdb) call inform (2147483641, "pre=2147483641") ../../src/gcc/testsuite/c-c++-common/pr69453.c: In function ‘test’: ../../src/gcc/testsuite/c-c++-common/pr69453.c:6:5: note: pre=2147483641 _Pragma ("GCC diagnostic ignored \"-Wmaybe-uninitialized\"") ^ ../../src/gcc/testsuite/c-c++-common/pr69453.c:13:3: note: in expansion of macro ‘YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN’ YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN ^ (gdb) p /x 2147483641 $15 = 0x7ffffff9 (gdb) call inform (2147483656, "post=2147483656") ../../src/gcc/testsuite/c-c++-common/pr69453.c:14:12: note: post=2147483656 *++yyvsp = yylval; ~~~~~~~~~^~~~~~~~ (gdb) p /x 2147483656 $8 = 0x80000008 (gdb) p l0 $16 = 2147483641 (gdb) p l1 $17 = 312096 (gdb) p /x l0 $18 = 0x7ffffff9 Then, after the call to: 1338 if ((pre_virtual_p = linemap_location_from_macro_expansion_p (set, l0))) 1339 l0 = linemap_resolve_location (set, l0, 1340 LRK_MACRO_EXPANSION_POINT, 1341 NULL); 1342 we have: (gdb) p /x l0 $21 = 0x80000004 so we have a comparison of locations, one (l0) from a macro expansion, the other not (l1). linemap_compare_locations concludes by executing this: 1368 return l1 - l0; giving this rather nonsensical result: Value returned is $25 = -2147171556 If I'm reading this right, it thus regards the "ignored" as happening *after* the source line of interest, hence the latter erroneously isn't affected by the _Pragma.
(In reply to David Malcolm from comment #1) linemap_compare_locations does the right thing if passed a pair of ordinary locations, or if both locations are within the same macro expansion. It generates nonsensical results if one of the locations is in a macro map, which is what's happening here (the location of the _Pragma, after r232893)
Author: jakub Date: Mon Feb 1 22:36:07 2016 New Revision: 233058 URL: https://gcc.gnu.org/viewcvs?rev=233058&root=gcc&view=rev Log: PR preprocessor/69543 PR c/69558 * c-pragma.c (handle_pragma_diagnostic): Pass input_location instead of loc to control_warning_option. * gcc.dg/pr69543.c: New test. * gcc.dg/pr69558.c: New test. Added: trunk/gcc/testsuite/gcc.dg/pr69543.c trunk/gcc/testsuite/gcc.dg/pr69558.c Modified: trunk/gcc/c-family/ChangeLog trunk/gcc/c-family/c-pragma.c trunk/gcc/testsuite/ChangeLog
Workaround applied, keeping this open to fix it for real for GCC 7.
Author: dmalcolm Date: Tue Feb 23 17:39:16 2016 New Revision: 233637 URL: https://gcc.gnu.org/viewcvs?rev=233637&root=gcc&view=rev Log: Add test coverage for _Pragma (PR preprocessor 69126, 69543, 69558) We had some regressions in the ability for _Pragma to disable a warning (PR preprocessor/69126, PR preprocessor/69543, PR preprocessor/69558). This patch attempts to add more test coverage for this, for the various combinations of: - various warnings: -Wunused-variable -Wuninitialized -Wdeprecated-declarations - various combinations of location of _Pragma relative to location of the warning: - _Pragma is in a macro, warning isn't a macro - neither is in a macro - _Pragma isnt't in a macro, warning is in a macro - in different macros - both in the same macro - C vs C++ frontend. It adds some XFAILs: - pr69543-1.c for C++ (fixed in the followup patch) - pr69543-3.c for both C and C++ - pr69543-4.c for both C and C++ - pr69558.c for C++ (moving it from gcc.dg to c-c++-common, marking it as xfail for C++ for now) gcc/testsuite/ChangeLog: PR preprocessor/69126 PR preprocessor/69543 PR preprocessor/69558 * c-c++-common/pr69126.c (MACRO_1, test_1): New. (f): Rename to... (test_2): ...this, and add leading comment. (MACRO_3, test_3): New. (MACRO_4A, MACRO_4B, test_4): New. (MACRO): Rename to... (MACRO_5): ...this. (g): Rename to... (test_5): ...this, updating for renaming of MACRO, and add leading comment. * c-c++-common/pr69543-1.c: New. * c-c++-common/pr69543-2.c: New. * c-c++-common/pr69543-3.c: New. * c-c++-common/pr69543-4.c: New. * c-c++-common/pr69558-1.c: New. * c-c++-common/pr69558-2.c: New. * c-c++-common/pr69558-3.c: New. * c-c++-common/pr69558-4.c: New. * gcc.dg/pr69558.c: Move to... * c-c++-common/pr69558.c: ...here. Add dg-bogus directives, with xfail for c++. Added: trunk/gcc/testsuite/c-c++-common/pr69543-1.c trunk/gcc/testsuite/c-c++-common/pr69543-2.c trunk/gcc/testsuite/c-c++-common/pr69543-3.c trunk/gcc/testsuite/c-c++-common/pr69543-4.c trunk/gcc/testsuite/c-c++-common/pr69558-1.c trunk/gcc/testsuite/c-c++-common/pr69558-2.c trunk/gcc/testsuite/c-c++-common/pr69558-3.c trunk/gcc/testsuite/c-c++-common/pr69558-4.c trunk/gcc/testsuite/c-c++-common/pr69558.c - copied, changed from r233636, trunk/gcc/testsuite/gcc.dg/pr69558.c Removed: trunk/gcc/testsuite/gcc.dg/pr69558.c Modified: trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/c-c++-common/pr69126.c
Author: dmalcolm Date: Tue Feb 23 17:44:28 2016 New Revision: 233638 URL: https://gcc.gnu.org/viewcvs?rev=233638&root=gcc&view=rev Log: PR preprocessor/69126: avoid comparing ad-hoc and non-ad-hoc locations gcc/testsuite/ChangeLog: PR preprocessor/69126 PR preprocessor/69543 * c-c++-common/pr69126-2-long.c: New test. * c-c++-common/pr69126-2-short.c: New test. * c-c++-common/pr69543-1.c: Remove xfail. libcpp/ChangeLog: PR preprocessor/69126 PR preprocessor/69543 * line-map.c (linemap_compare_locations): At the function top, replace inlined bodies of get_location_from_adhoc_loc with calls to get_location_from_adhoc_loc. Add a pair of calls to get_location_from_adhoc_loc at the bottom of the function, to avoid meaningless comparisons of ad-hoc and non-ad-hoc locations. Added: trunk/gcc/testsuite/c-c++-common/pr69126-2-long.c trunk/gcc/testsuite/c-c++-common/pr69126-2-short.c Modified: trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/c-c++-common/pr69543-1.c trunk/libcpp/ChangeLog trunk/libcpp/line-map.c
Is still an issue, or has it been properly fixed with dmalcolm's latest commits to the PR?
The following testcases still have xfails: c-c++-common/pr69543-3.c c-c++-common/pr69543-4.c so this isn't quite fixed yet.
(In reply to David Malcolm from comment #8) > The following testcases still have xfails: > c-c++-common/pr69543-3.c > c-c++-common/pr69543-4.c > so this isn't quite fixed yet. These XFAILs are fixed (for both C and C++) by deleting these lines within tree-ssa-uninit.c:warn_uninit: 175 location = linemap_resolve_location (line_table, location, 176 LRK_SPELLING_LOCATION, NULL); so that the location used for the warning retains any virtual location, rather than flattening it to the physical location. Am not yet sure of the impact of such a change.
The lines in comment #9 came from 18f0e0e551a995687e1822aabb9b7d7ee8f11492 aka r186971 (affecting gcc.dg/cpp/pragma-diagnostic-2.c)
(In reply to David Malcolm from comment #10) > The lines in comment #9 came from 18f0e0e551a995687e1822aabb9b7d7ee8f11492 > aka r186971 (affecting gcc.dg/cpp/pragma-diagnostic-2.c) This was: "[PATCH 07/11] Fix -Wuninitialized for -ftrack-macro-expansion" * "https://gcc.gnu.org/ml/gcc-patches/2012-04/msg00574.html' as part of this kit: "Patches to enable -ftrack-macro-expansion by default" * https://gcc.gnu.org/ml/gcc-patches/2012-04/msg00532.html
GCC 8.1 has been released.
GCC 8.2 has been released.
David: Can the bug be marked as resolved?
GCC 8.3 has been released.
GCC 8.4.0 has been released, adjusting target milestone.
GCC 11.1 has been released, retargeting bugs to GCC 11.2.
GCC 11.2 is being released, retargeting bugs to GCC 11.3
GCC 11.3 is being released, retargeting bugs to GCC 11.4.
See PR97498 which is closely related to this. It seems that the use of input_location while handling diagnostic pragmas is problematic in other cases besides the one discussed here (i.e. also when processing a diagnostic pop.) Here is a test case from that PR, which breaks because of the input_location workaround discussed here though: ====== static void f() {} _Pragma("GCC diagnostic error \"-Wunused-function\"") ====== The above errors for C but not C++, because in C, input_location points to the start of the line and so it takes effect too early.
The master branch has been updated by Lewis Hyatt <lhyatt@gcc.gnu.org>: https://gcc.gnu.org/g:b52b99b62df8fc9b3a3010cb0a8cf49bc35037f0 commit r13-2994-gb52b99b62df8fc9b3a3010cb0a8cf49bc35037f0 Author: Lewis Hyatt <lhyatt@gmail.com> Date: Fri Sep 30 14:10:00 2022 -0400 diagnostics: Fix virtual location for -Wuninitialized [PR69543] Warnings issued for -Wuninitialized have been using the spelling location of the problematic usage, discarding any information on the location of the macro expansion point if such usage was in a macro. This makes the warnings impossible to control reliably with #pragma GCC diagnostic, and also discards useful context in the diagnostic output. There seems to be no need to discard the virtual location information, so this patch fixes that. PR69543 was mostly about _Pragma issues which have been fixed for many years now. The PR remains open because two of the testcases added in response to it still have xfails, but those xfails have nothing to do with _Pragma and rather just with the issue fixed by this patch, so the PR can be closed now as well. The other testcase modified here, pragma-diagnostic-2.c, was explicitly testing for the undesirable behavior that was xfailed in pr69543-3.c. I have adjusted that and also added a new testcase verifying all 3 types of warning that come from tree-ssa-uninit.cc get the proper location information now. gcc/ChangeLog: PR preprocessor/69543 * tree-ssa-uninit.cc (warn_uninit): Stop stripping macro tracking information away from the diagnostic location. (maybe_warn_read_write_only): Likewise. (maybe_warn_operand): Likewise. gcc/testsuite/ChangeLog: PR preprocessor/69543 * c-c++-common/pr69543-3.c: Remove xfail. * c-c++-common/pr69543-4.c: Likewise. * gcc.dg/cpp/pragma-diagnostic-2.c: Adjust test for new behavior. * c-c++-common/pragma-diag-16.c: New test.