On Tue, Aug 12, 2008 at 10:58 PM, Santosh Pradhan
<santosh.pradhan@xxxxxxxxx> wrote:
> Hi All,
> I am new to this group and I have a question regarding following C program.
>
> #include<stdio.h>
>
> #define NAME "santosh"
>
> int main()
> {
> char *p_name = NAME;
> char *q_name = NAME;
> if (p_name == q_name)
> printf("Hello, World\n");
> return 0;
> }
>
> When I compile this test program, it always prints "Hello, World".
>
> My Question:
>
> i) Does compiler do any optimization automatically to make both the pointers
> have same address ?
>
> ii) How does this happen?
>
> iii) Will both the pointers be same always?
I don't know much of assembly but it looks like gcc is optimizing
it......See the below assembly for your code
/home/mkatiyar> gcc -S d.c
/home/mkatiyar> cat d.s
.file "d.c"
.section .rodata
.LC0:
.string "santosh"
.LC1:
.string "Hello, World"
.text
.globl main
.type main, @function
main:
leal 4(%esp), %ecx
andl $-16, %esp
pushl -4(%ecx)
pushl %ebp
movl %esp, %ebp
pushl %ecx
subl $20, %esp
movl $.LC0, -8(%ebp) <<============ p_name
movl $.LC0, -12(%ebp) <<============ q_name
movl -8(%ebp), %eax
cmpl -12(%ebp), %eax
...............
...............
Both have been assigned the same address of LC0. I tried compiling it
with various other options and every time it generates the same
assembly for it, so I guess it will be same always. Prehaps someone
more knowledgeable with internals of gcc will throw more light on
this.
Thanks -
Manish
>
> iv) Will it differ in other platforms like prop. Unix (AIX/HP-UX etc.) and
> Win?
>
> Any kind of help is appreciated.
>
> Sorry, if it is not the right place to ask this :(.
>
> Thanks in advance.
>
> Regards,
> Santosh
>
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