Thread: strings in C

when you have a program like:

Code:

#include <stdio.h>
int main()
{
	printf("This is my string\n");
	return 0;
}

I was wondering exactly how it compiles with the string in the middle of the code. I had THIS idea:
It runs through the code building the tokens etc. It takes the string, "This is my string\n" and puts it in the TXT memory and then when the program calls the std printf() it replaces the string I typed with a pointer to that area in memory.

I just want to know how it really works. If anyone could explain it or point me to a place where I could discover it, that would be appreciated. Thank you

-LC

yeah but if you disassemble it it doesnt say

Code:

    call printf("lala");

I think it says...

Code:

    .text:
        .string  "This is my string\n"
    main:
       ...
        movl  .string, %eax ; I think .string is the ptr to the addr of the string in mem
        call printf
       ...

So doesn't that mean that printf really just calls with the parameter of the pointer to my string rather than the string itself?

-LC

Within the executable are directories into the various data sections, including the ones marked with flags such as whether the section is readable, writable, executable and so forth. When the linker recalculates addresses it never touches the initialized, static variables anyway. And it's movl %eax, .string, not the other way around. Oh well.

also you have linux, so you can look through the glibc source code...or download it from gnu.org

of course this wont show teach you about the executable structure etc... but you can see how the function works.

Originally posted by Lynux-Penguin
when you have a program like:

Code:

#include <stdio.h>
int main()
{
	printf("This is my string\n");
	return 0;
}

I was wondering exactly how it compiles with the string in the middle of the code. I had THIS idea:
It runs through the code building the tokens etc. It takes the string, "This is my string\n" and puts it in the TXT memory and then when the program calls the std printf() it replaces the string I typed with a pointer to that area in memory.

I just want to know how it really works. If anyone could explain it or point me to a place where I could discover it, that would be appreciated. Thank you

-LC

You are essentially correct