gcc is allocating more stack space than needed. It seems to be bug similar to
bug 9624.
C test code.
------------
1 #include <stdio.h>
2
3 void function1() {
4 char a;
5 }
6
7 int main() {
8 function1();
9 }
Assembly Output
----------------
1 .file "test1.c"
2 .text
3 .globl function1
4 .type function1, @function
5 function1:
6 pushl %ebp
7 movl %esp, %ebp
8 subl $16, %esp <----- 16 bytes for a char??
9 leave
10 ret
11 .size function1, .-function1
12 .globl main
13 .type main, @function
14 main:
15 leal 4(%esp), %ecx
16 andl $-16, %esp
17 pushl -4(%ecx)
18 pushl %ebp
19 movl %esp, %ebp
20 pushl %ecx
21 call function1
22 popl %ecx
23 popl %ebp
24 leal -4(%ecx), %esp
25 ret
26 .size main, .-main
27 .ident "GCC: (GNU) 4.2.4 (Ubuntu 4.2.4-1ubuntu3)"
28 .section .note.GNU-stack,"",@progbits
gcc -v output
-------------
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr
--enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--with-gxx-include-dir=/usr/include/c++/4.2 --program-suffix=-4.2
--enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr
--enable-targets=all --enable-checking=release --build=i486-linux-gnu
--host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.2.4 (Ubuntu 4.2.4-1ubuntu3)
--
Summary: Stack allocation in the assembly output is more than
needed.
Product: gcc
Version: 4.2.4
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: nascent dot mind at gmail dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39428
