This issue is closely related to #61144, but seems to have appeared earlier. Consider the following test case: static int dummy = 0; extern int foo __attribute__((__weak__, __alias__("dummy"))); typedef char check[2*!__builtin_constant_p(dummy)-1]; typedef char check[2*!__builtin_constant_p(foo)-1]; While the static dummy could be considered constant if its address did not leak outside the translation unit, its address DOES leak via the weak alias foo. As long as there is no strong definition for foo in another translation unit, dummy may be externally modified via the alias foo. As for foo, it is external and thus may never be considered constant. Thus, __builtin_constant_p(dummy) and __builtin_constant_p(foo) should both yield zero and the above translation unit should compile successfully. The results observed vary highly with gcc version. A number of versions were observed giving __builtin_constant_p(dummy)==1, including 4.8.1, but __builtin_constant_p(foo) was more rare, showing up only in 4.9.0 and some really old versions like 4.4.7 (tested via gcc.godbolt.org since I don't have that many gcc versions lying around to test locally).
I should amend this report with further info: __builtin_constant_p is giving different results for dummy and foo depending on whether it's used at file scope or in a function. I've also observed some other really weird behavior from it that I need to summarize and report.
I think this has been fixed with last alias reorg, but double-checking and having a testcase would be nice.
Fixed.
Author: hubicka Date: Sun Sep 11 12:15:02 2016 New Revision: 240082 URL: https://gcc.gnu.org/viewcvs?rev=240082&root=gcc&view=rev Log: PR ipa/61159 * compile/pr61159.c: New testcase Added: trunk/gcc/testsuite/gcc.c-torture/compile/pr61159.c Modified: trunk/gcc/testsuite/ChangeLog
The new testcase FAILs on Solaris/x86 with /bin/as: FAIL: gcc.c-torture/compile/pr61159.c -O0 (test for excess errors) Excess errors: Assembler: pr61159.c "/var/tmp//ccRtFPva.s", line 5 : Cannot set a weak symbol to a common symbol Input is .file "pr61159.c" .local dummy .comm dummy,4,4 .weak foo .set foo,dummy Rainer
Can the bug be marked as resolved?
> --- Comment #6 from Martin Liška <marxin at gcc dot gnu.org> --- > Can the bug be marked as resolved? No, the Solaris/x86 problem persists.
The master branch has been updated by Rainer Orth <ro@gcc.gnu.org>: https://gcc.gnu.org/g:a25d7d1385087e0f43574064db45f1bc7d52f400 commit r14-9176-ga25d7d1385087e0f43574064db45f1bc7d52f400 Author: Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> Date: Mon Feb 26 10:42:04 2024 +0100 testsuite: xfail gcc.c-torture/compile/pr61159.c on Solaris/x86 with as [PR61159] gcc.c-torture/compile/pr61159.c currently FAILs on 32 and 64-bit Solaris/x86 with the native assembler: FAIL: gcc.c-torture/compile/pr61159.c -O0 (test for excess errors) FAIL: gcc.c-torture/compile/pr61159.c -O1 (test for excess errors) FAIL: gcc.c-torture/compile/pr61159.c -O2 (test for excess errors) FAIL: gcc.c-torture/compile/pr61159.c -O2 -flto (test for excess errors) FAIL: gcc.c-torture/compile/pr61159.c -O2 -flto -flto-partition=none (test for excess errors) FAIL: gcc.c-torture/compile/pr61159.c -O3 -g (test for excess errors) FAIL: gcc.c-torture/compile/pr61159.c -Os (test for excess errors) Excess errors: Assembler: pr61159.c "/var/tmp//ccRtFPva.s", line 5 : Cannot set a weak symbol to a common symbol This is a bug/limitation in the native assembler. Given that this hasn't seen fixes for a long time, this patch xfails the test. Tested on i386-pc-solaris2.11 (as and gas) and x86_64-pc-linux-gnu. 2024-02-24 Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> gcc/testsuite: PR ipa/61159 * gcc.c-torture/compile/pr61159.c: xfail on Solaris/x86 with as.
Test xfail'ed on Solaris/x86 with as for GCC 14.0.1.