https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63890
Bug ID: 63890
Summary: [4.9/5.0 regression] Compiling trivial program with -O
-p leads to misaligned stack
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: fxcoudert at gcc dot gnu.org
Created attachment 33985
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33985&action=edit
Assembler generated by trunk compiler with "-m32 -O -p"
Compile the following trivial program with trunk (rev. 217599) or the released
4.9.2 gcc leads to runtime segfault, on x86_64-apple-darwin14:
$ cat a.c
int main (void) { __builtin_exit (0); }
$ ./bin/gcc -m32 -O -p a.c && ./a.out
zsh: segmentation fault ./a.out
This shows up as a failure of gcc.dg/20021014-1.c in the testsuite results
(https://gcc.gnu.org/ml/gcc-testresults/2014-11/msg01533.html).
Removing -p, or -O, or compiling for 64-bit doesn't trigger the bug. The
backtrace is:
* frame #0: 0x9036f440 libdyld.dylib`misaligned_stack_error_
frame #1: 0x00001f75 a.out`main + 17
frame #2: 0x903716d9 libdyld.dylib`start + 1
Comparing the generated assembly by the trunk compiler (bad-trunk.s) with that
generated by the 4.8.3 compiler (ok-48.s) shows the difference is simple:
--- ok-48.s 2014-11-15 16:17:55.000000000 +0100
+++ bad-trunk.s 2014-11-15 16:17:44.000000000 +0100
@@ -1,4 +1,4 @@
- .text
+ .section __TEXT,__text_startup,regular,pure_instructions
.globl _main
_main:
LFB0:
@@ -7,12 +7,12 @@ LCFI0:
movl %esp, %ebp
LCFI1:
pushl %ebx
- subl $20, %esp
+ subl $16, %esp
LCFI2:
call ___x86.get_pc_thunk.bx
L1$pb:
call mcount
- movl $0, (%esp)
+ pushl $0
call _exit
LFE0:
.section __TEXT,__textcoal_nt,coalesced,pure_instructions
