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From: "su at cs dot ucdavis.edu" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/59801] GCC does not warn on unused global variable Date: Thu, 16 Jan 2014 06:08:00 -0000 [thread overview] Message-ID: <bug-59801-4-MhKIJFPu8I@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-59801-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59801 Zhendong Su <su at cs dot ucdavis.edu> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |su at cs dot ucdavis.edu --- Comment #3 from Zhendong Su <su at cs dot ucdavis.edu> --- For the given code, it does seem make sense to issue a warning (whether or not "volatile" is used) because this is likely a bug in the code. $ gcc-trunk -Wunused-variable small.c $ clang-trunk -Wunused-variable small.c small.c:1:21: warning: unused variable 'a' [-Wunused-variable] static volatile int a; ^ 1 warning generated. $ cat small.c static volatile int a; int main () { return 0; } ---------------------- This also seems to be a missed optimization opportunity: $ gcc-trunk -O3 -S small.c $ cat small.s .file "small.c" .section .text.unlikely,"ax",@progbits .LCOLDB0: .section .text.startup,"ax",@progbits .LHOTB0: .p2align 4,,15 .globl main .type main, @function main: .LFB0: .cfi_startproc xorl %eax, %eax ret .cfi_endproc .LFE0: .size main, .-main .section .text.unlikely .LCOLDE0: .section .text.startup .LHOTE0: .local a .comm a,4,4 .ident "GCC: (GNU) 4.9.0 20140115 (experimental) [trunk revision 206638]" .section .note.GNU-stack,"",@progbits
next prev parent reply other threads:[~2014-01-16 6:08 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-01-14 8:26 [Bug c/59801] New: " chengniansun at gmail dot com 2014-01-14 9:02 ` [Bug c/59801] " jakub at gcc dot gnu.org 2014-01-14 17:32 ` chengniansun at gmail dot com 2014-01-16 6:08 ` su at cs dot ucdavis.edu [this message] 2014-01-16 6:33 ` pinskia at gcc dot gnu.org 2014-01-16 6:34 ` pinskia at gcc dot gnu.org 2014-01-16 6:52 ` su at cs dot ucdavis.edu 2014-01-16 8:38 ` jakub at gcc dot gnu.org 2014-01-16 21:18 ` su at cs dot ucdavis.edu 2014-01-16 21:27 ` jakub at gcc dot gnu.org
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