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1. Check endianness

   int n = 1;
   int isLittleEndian = (*(char *)&n == 1);
   

2. Inline assembly with Intel syntax

   // $ gcc -m32 -fasm-blocks asm.c -o asm
   
   #include <stdio.h>
   
   int main (int argc, char *argv[]) {
   
       int espValue;
   
       _asm {
             mov [espValue], esp;
       }
   
       printf("espValue: %u\n", espValue);
   
       return 0;
   }
   

3. Return address of the current function

   void x() {
       void *returnAddress = __builtin_return_address(0);
       printf("%p\n", returnAddress);
   }
   

   The level argument is number of frames to scan up the call stack.

   See http://gcc.gnu.org/onlinedocs/gcc/Return-Address.html.

4. Size of an array on the stack

   int a[3]= { 1, 2, 3 };
   int len = sizeof(a)/sizeof(*a);