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From: "gccbugs at dima dot secretsauce.net" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/97261] New: gcc-10 produces invalid -Warray-bounds warning Date: Thu, 01 Oct 2020 03:32:14 +0000 [thread overview] Message-ID: <bug-97261-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97261 Bug ID: 97261 Summary: gcc-10 produces invalid -Warray-bounds warning Product: gcc Version: 10.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: gccbugs at dima dot secretsauce.net Target Milestone: --- Hi. I'm seeing gcc-10 flag a warning that I'm pretty sure is incorrect. gcc-9 and older did not warn about this (although that's probably because they weren't looking for these kinds of problems). Recipe: 1. save the attached as tst.c 2. gcc-10 -Wall -Wextra -Wno-unused-variable -fPIC -O3 -c -o tst.o tst.c I see this: tst.c: In function 'f': tst.c:21:17: warning: array subscript -1 is outside array bounds of 'double[1]' [-Warray-bounds] 21 | const ab_t* ab = (ab_t*)(pb - 1); | ^~ tst.c:16:13: note: while referencing 'b' 16 | double b = 4.; | ^ I believe this is false. Inside g(), ab->a is indeed out-of-bounds, but ab->b is not. And I only use ab->b. Taking away -fPIC or -O3 makes the warning go away. Making g() static makes it go away also. I'm using gcc-10 from Debian. Package version 10.1.0-5. Thanks!
next reply other threads:[~2020-10-01 3:32 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-01 3:32 gccbugs at dima dot secretsauce.net [this message] 2020-10-01 3:32 ` [Bug c/97261] " gccbugs at dima dot secretsauce.net 2020-10-01 6:26 ` rguenth at gcc dot gnu.org 2020-10-01 7:06 ` gccbugs at dima dot secretsauce.net 2020-10-01 7:54 ` rguenth at gcc dot gnu.org 2020-10-01 15:18 ` [Bug c/97261] distinguish invalid subscripts from invalid addresses in -Warray-bounds msebor at gcc dot gnu.org
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