----- Original Message -----
From: "Brian Dessent" <brian@xxxxxxxxxxx>
To: "Michael Gong" <mwgong@xxxxxxxxxxxxxx>
Cc: <gcc-help@xxxxxxxxxxx>
Sent: Friday, April 20, 2007 12:28 PM
Subject: Re: where is the string literal allocated ? On the stack ?
Michael Gong wrote:
Though it's not related with gcc, could anyone help me with following
question:
Where is the string literal allocated ? Is it on the stack ?
For example, where is "abc" allocated ?
char * foo() {
return "abc";
}
Everyone else has already answered your question directly, but I'd
like
to point out that the compiler is not a black box -- you can easily
see
exactly what it's doing with a few simple commands. Check the docs
for
on -S, -save-temps, -fverbose-asm, etc. For example:
$ echo 'char * foo() { return "abc"; }' | gcc -x c - -S -o
-
.file ""
.section .rodata
.LC0:
.string "abc"
.text
.globl foo
.type foo, @function
foo:
pushl %ebp
movl %esp, %ebp
movl $.LC0, %eax
popl %ebp
ret
.size foo, .-foo
.ident "GCC: (GNU) 4.0.4 20060507 (prerelease) (Debian
4.0.3-3)"
.section .note.GNU-stack,"",@progbits
As you can see, it goes in the .rodata section. The above is the
behavior under linux, but for PE (Win32) it is a different section:
$ echo 'char * foo() { return "abc"; }' | gcc -x c - -S -o -
.file ""
.section .rdata,"dr"
LC0:
.ascii "abc\0"
.text
.globl _foo
.def _foo; .scl 2; .type 32; .endef
_foo:
pushl %ebp
movl %esp, %ebp
movl $LC0, %eax
popl %ebp
ret
That is my second point: this kind of thing is platform-dependant
(although it can never be on the stack), and you didn't mention at all
what platform you are using in your original question, which should be
a
requirement for almost any compiler/toolchain question.
Brian
Thanks for the comments.
Actually, I don't care about the exact location :-) All I need to know
is whether it is on the stack. Therefore, I don't mention the platform
in the question.
Mike
