Dead Variables C

Question

I am working on some kind of private code that I cannot show, but I have made some code examples to describe my problem:

main.c:

#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <stdint.h>

typedef uint32_t (*FuncPtr)(char *s, uint32_t n);

uint32_t doSomething(char *s, uint32_t n){ 
    printf("n is %d in doSomething\n", n);
    printf("s is '%s' in doSomething\n\n", s);
    return 0;

}

uint32_t func1(char *s, uint32_t n){
    printf("n is %d in func1\n", n);
    printf("s is '%s' in func1\n\n", s);
    return doSomething(s, n);
}

uint32_t func2(char *s, uint32_t n){
    printf("n is %d in func2\n", n);
    printf("s is '%s' in func2\n\n", s);
    return doSomething(s, n);
}

uint32_t func3(char *s, uint32_t n){
    printf("n is %d in func3\n", n);
    printf("s is '%s' in func3\n\n", s);
    return doSomething(s, n);
}

void perform(FuncPtr fp, char *s, uint32_t n){
    printf("fp is location in %p\n", fp);
    printf("n is %d in perform\n", n);
    printf("s is '%s' in perform\n\n", s);
    fp(s, n);
}

int main(void) {

    srand(time(NULL));
    uint32_t r = (uint32_t)(rand() % 3 + 1);
    uint32_t n = (uint32_t)(rand() %100);
    char *s = "some string here";

    printf("r is %d\n", r);
    printf("n is %d in main\n", n);
    printf("s is '%s' in main\n\n", s);

    switch(r)
    {
        case 1:
            perform(func1, s, n);
            break;
        case 2:
            perform(func2, s, n);
            break;
        case 3:
            perform(func3, s, n);
            break;
    }

    return 0;
}

Here's the call stack:

 0  func1(s=0x9abcdef0, n=0 << Dead >>) [..\main.c:9,1]
 1  perform(fp=0x12345678, s=0x9abcdef0, n=42)  [..\main.c:21,1]
 2  main()  [..\main.c:25,10]

As you can see from above, nwhich is passed in func1, << dead >>and does not match the value in perform, although the pointer salways rests at the same address, Why is this happening? I did not find a useful description of what a dead variable is anywhere. Is there any fix I can make for this code, or is it due to a lot of compiler and memory issues that I cannot implement here?

Answer 1

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