TrueStudio - Why does the link static library fail?

Question

I am using TrueStudio for my own stm32 project. I create 2 file foo.h and foo.c includes 2 functions

//foo.h
int add(int a, int b);
int sub(int a, int b);

and the implementation of timeout

//foo.c
#include "foo.h"

int add(int a, int b)
{
  return a + b;
}

int sub(int a, int b)
{
  return a - b;
}

After that, I used gcc to compile a static library foo.a. I continue to make the main file to implement the library to test.

//main.c
#include <stdio.h>
#include "foo.h"

int main(int argc, const char *argv[])
{
  int a = 100, b = 50;

  printf("sum is: %d\n", add(a,b));
  printf("sub is: %d\n", sub(a,b));

  return 0;
}

Next, I link the static foo lib to main.c to make an executable file using command is

gcc main.c foo.a -o main

I ran it and get the result is

sum is: 150
sub is: 50

That's worked fine prove my static lib was built successfully. I begin to create a project stm32 from stmcubeMX and linker to this foo.a and the error appeared.

undefined reference to 'add'
undefined reference to 'sub'

My full code and setting path and build bellow

//main.c in TrueStudio
#include "main.h"
#include "foo.h"

int main(void)
{
  HAL_Init();

  SystemClock_Config();

  int a = 200, b = 100;
  int _sum, _sub;

  _sum = add(a, b);
  _sub = sub(a, b);

  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
}

I am very grateful for any help, thanks!

Answer 1

Rename your foo.a file to libfoo.a, then change the C Linker -> Libraries -> Libraries to just foo with nothing in front or in the back. This should cause the final output to be -lfoo, which in turn causes linker to search for libfoo.a in the library search paths.