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@elazarl
Last active Apr 12, 2020
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This is a demonstration showing how to print stack size of a certain function
// We demonstrate how to get the stack usage of a function
// using the __builtin_frame_address function of GCC and clang.
//
// This function returns:
// The frame is the area on the stack that holds local variables and saved registers.
// The frame address is normally the address of the first word pushed on to
// the stack by the function.
//
// by saving its value and comparing it to a callee, we get the stack usage of this
// function.
//
// $ make stack_size
// cc stack_size.c -o stack_size
// $ ./stack_size
// stack size of big_func: 0x7ffee6b716e0-0x7ffee6b712d0 = 1040
// stack size of small_func: 0x7ffee6b716e0-0x7ffee6b716b0 = 48
#include <stdio.h>
void* last_frame_addr;
void
__attribute__ ((noinline))
_print_stack_size(const char* func_name) {
printf("stack size of %s: %p-%p = %ld\n",
func_name,
last_frame_addr,
__builtin_frame_address(0),
last_frame_addr-__builtin_frame_address(0));
}
#define print_stack_size() _print_stack_size(__func__)
volatile int sink;
void big_func()
{
char buf[1000];
int i;
last_frame_addr = __builtin_frame_address(0);
buf[0] = 1;
for (i=1;i<sizeof(buf);i++) {
buf[i] = i + buf[i-1];
}
print_stack_size();
for (i=0;i<sizeof(buf);i++) {
sink = buf[i];
}
}
void small_func()
{
char buf[10];
int i;
buf[0] = 1;
last_frame_addr = __builtin_frame_address(0);
for (i=1;i<sizeof(buf);i++) {
buf[i] = i + buf[i-1];
}
print_stack_size();
for (i=0;i<sizeof(buf);i++) {
sink = buf[i];
}
}
int main() {
big_func();
small_func();
}
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