When a variable length array is defined in a loop, a call of alloca() is placed in the loop, and causes stack overflow.
I believe this shouldn't happen since "The space for a variable-length array is deallocated as soon as the array name's scope ends." (quote from the doc) http://gcc.gnu.org/onlinedocs/gcc-4.3.5/gcc/Variable-Length.html $ cat test.c int const n = 10000; void g(int* p); void f(void) { int i; for (i = 0; i < 10000; ++i) { int a[n]; g(a); } } $ gcc --version gcc (GCC) 4.3.4 20090804 (release) 1 Copyright (C) 2008 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. $ uname -a CYGWIN_NT-5.1 prime 1.7.5(0.225/5/3) 2010-04-12 19:07 i686 Cygwin $ gcc -S -Os -o - test.c (snip) L2: movl %esp, %ebx call __alloca leal 19(%esp), %eax addl $1, %esi andl $-16, %eax movl %eax, (%esp) call _g cmpl $10000, %esi movl %ebx, %esp jne L2 (snip) -- Summary: Variable length array cause repeated alloca() in a loop Product: gcc Version: 4.3.4 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: k_satoda at f2 dot dion dot ne dot jp http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45528