gcc « assembly « C Q&A

1. Is GCC broken when taking the address of an argument on ARM7TDMI?    stackoverflow.com

My C code snippet takes the address of an argument and stores it in a volatile memory location (preprocessed code):

void foo(unsigned int x) {
    *(volatile unsigned int*)(0x4000000 + ...

2. How do I know if gcc agrees that something is volatile?    stackoverflow.com

Consider the following:

volatile uint32_t i;

3. Trouble understanding gcc's assembly output    stackoverflow.com

While writing some C code, I decided to compile it to assembly and read it--I just sort of, do this from time to time--sort of an exercise to keep me thinking ...

4. How to fetch the end address of my code    stackoverflow.com

I'm writing a real-time operation system from scratch for a course project. I want to know the end address of my code after I download it to the chip, because I ...

5. Using GCC to produce readable assembly?    stackoverflow.com

I was wondering how to use GCC on my C source file to dump a mnemonic version of the machine code so I could see what my code was ...

6. GCC generated assembly equivalent to continue statement in C    stackoverflow.com

When a continue statement is used inside a loop in C code, GCC creates a new label with a nop instruction right before the end of the loop block and jumps ...

7. Decoding equivalent assembly code of C code    stackoverflow.com

Wanting to see the output of the compiler (in assembly) for some C code, I wrote a simple program in C and generated its assembly file using gcc. The code is this: ...

8. DPPS on older version GCC    stackoverflow.com

Hei! I need to optimize some matrix multiplication code in c, and I'm doing it using SSE vector instructions. I also found that there exists SSE4.1 that already has instruction for dot-product, ...

9. GCC hotpatching?    stackoverflow.com

When I compile this piece of code

unsigned char A[] = {1, 2, 3, 4};

unsigned int
f (unsigned int x)
{
  return A[x];
}

mov edi, edi
movzx  eax, BYTE PTR A[rdi]
ret

10. Differences in dis-assembled C code of GCC and Borland?    stackoverflow.com

Recently I have gotten interested into dis-assembling C code (very simple C code) and followed a tutorial that used Borland C++ Compiler v 5.5 (compiles C code just fine) and everything ...

11. Why does LLVM add two extra instructions for the same program?    stackoverflow.com

I am compiling this C program and comparing the generated assembly code:

int main(){ return 0; }

_main:
LFB2:
    pushq   ...

12. Integrating Intel's icc with gcc    stackoverflow.com

okey i am stuck at a problem. Been using gcc to compiler/assemble my C codes for a while and got used to using Intel assembly syntax. used the "-masm=intel" flag when ...

13. GCC adds weird temporal variables    stackoverflow.com

I have created this code:

#include <stdio.h>

typedef unsigned int uint;
uint in[2]={1,2},out[2]={3,4};

int main() {

    in[0]=out[0]/10;
}

0000000000400474 <main>:
400474:   ...

14. disassembling simple code in C on LLVM GCC 4.2    stackoverflow.com

when I disassembled following simple program in C:

int main ()
{
 int a = 'a';
return 0;
}

Dump of assembler code for function main:
0x0000000100000f20 <main+0>:    push   rbp
0x0000000100000f21 ...

15. SIGSEGV in optimized version of code    stackoverflow.com

My knowledge of the intel instruction set is a bit rusty. Can you tell me why I might be getting a segmentation fault in the optimized version of my function ...

16. GCC option to get assembly code AND C code    cboard.cprogramming.com

17. Understading assembly code created by gcc    cboard.cprogramming.com

I'm supposed to get the assembly code from some C file with -S switch and then perform some tasks with that code, saying where is the start and end of a function including comments on the asm file, identify the records or memory cells where the variables where saved, presente the structure and content of the stack an some other things... ...