I am going to execute the below program
in the above program , where will store the variable "p" ? is it store in "Code segment" or "Data segment" ?Code:#include<stdio.h> int main { char *p="howareyou"; return 0; }
why it store in data segment, If it store in "Data segment", ?
Neither. p is an automatic local variable. It is automatically created at the start of main and disappears when main is done. It exists on the stack. The string it points to, however, should exist in the data segment. The code segment is just for machine instruction. The data segment is for data, like string literals.
HI Thanks for your reply.
Just I want to know the code segment starting pointing address and ending pointing address. is there any way to find these address details?
Why do you want to know this?Originally Posted by nkrao123@gmail.
Look up a C++ Reference and learn How To Ask Questions The Smart Way
Hi Light,
Actually I fell that "howareyou" would be store in Code(data) segment. while executing the code, i can find the address of "howareyou" by using the printf("%u\n",p).Code:#include<stdio.h> int main { char *p="howareyou"; printtf ("%u\n",p); return 0; }
so if i know the Code(data) segment starting point and end point, then the valud of "p" should be in between this values of staring and ending.
Hope you understand my point . Please let me know solutions for this.
Now on my machine, string constants end up in a section for read-only data (.rodata)Code:$ cat foo.c #include<stdio.h> int main () { char *p="aaaaaaaabbbbbbbb"; return 0; } $ gcc -c foo.c $ size foo.o text data bss dec hex filename 92 0 0 92 5c foo.o $ nm foo.o 0000000000000000 T main $ objdump -d foo.o foo.o: file format elf64-x86-64 Disassembly of section .text: 0000000000000000 <main>: 0: 55 push %rbp 1: 48 89 e5 mov %rsp,%rbp 4: 48 c7 45 f8 00 00 00 movq $0x0,-0x8(%rbp) b: 00 c: b8 00 00 00 00 mov $0x0,%eax 11: c9 leaveq 12: c3 retq $ objdump -s foo.o foo.o: file format elf64-x86-64 Contents of section .text: 0000 554889e5 48c745f8 00000000 b8000000 UH..H.E......... 0010 00c9c3 ... Contents of section .rodata: 0000 61616161 61616161 62626262 62626262 aaaaaaaabbbbbbbb 0010 00 . Contents of section .comment: 0000 00474343 3a202855 62756e74 7520342e .GCC: (Ubuntu 4. 0010 342e332d 34756275 6e747535 2920342e 4.3-4ubuntu5) 4. 0020 342e3300 4.3. Contents of section .eh_frame: 0000 14000000 00000000 017a5200 01781001 .........zR..x.. 0010 1b0c0708 90010000 1c000000 1c000000 ................ 0020 00000000 13000000 00410e10 4386020d .........A..C... 0030 06000000 00000000 ........
Some other machines would put string constants into the code section.
Some ancient fossils would put them in the data section.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
nkr, you haven't answered laserlight's question. All you have done is reiterate what you want to do. Laserlight asked you why want to do that.
Given your obvious ducking of the question, I will assume your reason is the same as others who ask what you have. That reason is generally malicious, unethical, or illegal, such as a desire to write a virus, trojan horse, or a self-modifying (and therefore mutating) executable. And that is against the guidelines of this site. Refer, specifically, to point 6 in the forum guidelines.
Last edited by grumpy; 02-04-2012 at 12:32 AM.
Hi Salem,
I goggled some material and understand the below things.
1. code segment ( mostly it is Read only . often it have readwrite also) ( can you let me know one small example for readwrite scenario?)
2. data segment
a. Initialized data segment ( it has read or readwrite)
b. unInitialized data segment ( it has read or readwrite)
4. stack
5. Heap.
in your above example " char *p="aaaaaaaabbbbbbbb"; " goes to code segment or Data segment ?
Hi salem,
I have one more doubt. Till now i know only code, data, stack and heap segments. .rodata is new segment or how it is? pleace can you explain me little bit more about it. i gone through the URL (http://www.bravegnu.org/gnu-eprog/c-startup.html ). but i did not understand much.
Thanks in advance
Last edited by nkrao123@gmail.; 02-04-2012 at 01:30 AM.
Hi Light/Grumpy,
Actually my thing is to verify that "howareyou" address is in code segment. Thats why if i know the code segment staring address and ending address. According that i can validate that one as "howareyou" would be in that segment. that is my intention .
