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Stub Functions

002_06: How can I change the value of a file static variable from a stub function in a different source file?

Question:

The function I am testing uses a static variable. I want to change the value of the static variable from a stub function, but since the source files are different, the static variable cannot be accessed from the stub function. Is there a workaround for this?

Answer:

For example, consider the function test_sample() and the sub-function sub_sample() below. 

----- source.c ----
static int val=0; /* cannot access from stub source file */

void test_sample(void)
{
    val = 0; /* initialized */

    sub_sample(); /* the value of "val" is changed within sub_sample() */

    if( val = 0 )
    {
        /* branch procedure 0 */
    }
    else
    {
        /* branch procedure 1 */
    }
}

void sub_sample(void)
{
    /* procedure to change value of "val" */
}

Since the stub function to replace sub_sample() resides in a different source file, the static variable "val" cannot be accessed directly. Therefore, we will use the method described below to indirectly access static variable "val".

1. Create a pointer to a global variable of the same type as "static int val" in the stub function source file.
2. Use the pointer within the stub function to change the value. 

--AMSTB_SrcFile.c--

int *ptr_val;

void AMSTB_test_sub(void)
{
    static int INPUT_param;   /* create a variable to enter input test data */
    ptr_val[0] = INPUT_param; /* assign the input test data to ptr_val[0] */
}

3. Add to the CSV file’s input variables:
  "ptr_val" (add by "Address" setting)
  "ptr_val[0]" (add by "Pointer with Index" setting).
  "INPUT_param"

4. In the test data for "ptr_val" enter the address of the static variable val. Since the address can be entered by symbol name, enter "source.c /val" to enter the address for static variable val. As a result, during test execution ptr_val points to the same address as static variable val, and ptr_val[0] is the same memory as val.

Note: The format for file static variables is [source filename]/[variable name].

5. In "INPUT_param", enter the test data you want to assign to val.

As a result, when executing the stub function for sub_sample(), the data entered for INPUT_param is assigned to ptr_val[0]. But since ptr_val[0] points to the same memory as "val" you can change the value of "val" from the stub function.

 

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