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From: "jtc at acorntoolworks dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/18260] New: generated code uses memory beyond allocated stack frame. Date: Mon, 01 Nov 2004 00:08:00 -0000 [thread overview] Message-ID: <20041101000818.18260.jtc@acorntoolworks.com> (raw) A co-worker testing MySQL 4 on NetBSD/amd64 was having trouble with random crashes. He tracked the crashes down to mf_radix.c:radixsort_for_str_ptr(), and handed the problem off to me for further analysis. I cut down mf_radix.c (attached to this bug report), and looked at the code generated with "gcc -O2 -S mf_radix.c". It appears that the memory for local variables is not accounted for entirely correctly. There are 1024+ bytes of local variables, but the stack pointer (%rsp) is only adjusted by 912 bytes. And it appears local variable "count" is referenced before the stack pointer (-120(%rsp)). I believe, but have not yet confirmed, that the crashes occur because something in NetBSD's thread/task switch code is overwriting the values below the stack pointer assuming that it is free for temporary use. This may also effect other systems --I've done the same in embedded kernels I've written in the past. NetBSD 2.0RC4 uses a modified version of gcc 3.3.3, so I have confirmed that the problem still exists with unmodified gcc 3.3.5. Linking in versions of mf_radix.c compiled without optimization or with gcc 3.4 eliminates the crashes. My attempts to build MySQL 4 entirely with gcc 3.4.X have not been successful, but I have not had enough time to investigate why. -- Summary: generated code uses memory beyond allocated stack frame. Product: gcc Version: 3.3.5 Status: UNCONFIRMED Severity: normal Priority: P2 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: jtc at acorntoolworks dot com CC: gcc-bugs at gcc dot gnu dot org GCC host triplet: i386-netbsd GCC target triplet: amd64-netbsd http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18260
next reply other threads:[~2004-11-01 0:08 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2004-11-01 0:08 jtc at acorntoolworks dot com [this message] 2004-11-01 0:11 ` [Bug rtl-optimization/18260] " pinskia at gcc dot gnu dot org 2004-11-01 0:21 ` jtc at acorntoolworks dot com 2004-11-01 13:06 ` falk at debian dot org 2004-11-01 22:45 ` jtc at acorntoolworks dot com
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