unused symbols and GCC

all.c

#include <stdio.h>

int used(void)
{
    printf("all used\n");
    return 0;
}

int unused(void)
{
    printf("all unused\n");
    return 9000;
}

int unrelated(void)
{
    return 42;
}

int main(int argc, char **argv)
{
    return used();
}

build

#!/usr/bin/env bash

# Compile
gcc -o all.o -c all.c
gcc -o main.o -c main.c
gcc -o helper.o -c helper.c
gcc -o unrelated.o -c unrelated.c

# Archive
rm -f helper.a # ar has no option to completely overwrite existing file
ar rcf helper.a helper.o
rm -f unrelated.a
ar rcf unrelated.a unrelated.o

# Link
gcc -o test1 all.o
gcc -o test2 main.o helper.o unrelated.o
gcc -o test3 main.o helper.a unrelated.a

# Tests
echo Same object file
nm test1 | grep "\b\(unused\|used\|unrelated\)\b"

echo Separate object file
nm test2 | grep "\b\(unused\|used\|unrelated\)\b"

echo Separate archived object file
nm test3 | grep "\b\(unused\|used\|unrelated\)\b"

helper.c

#include <stdio.h>

int used(void)
{
    printf("used\n");
    return 0;
}

int unused(void)
{
    printf("unused\n");
    return 9000;
}

main.c

int used(void);

int main(int argc, char **argv)
{
    return used();
}

results.txt

Same object file
0000000000400550 T unrelated
000000000040053b T unused
0000000000400526 T used
Separate object file
0000000000400566 T unrelated
0000000000400551 T unused
000000000040053c T used
Separate archived object file
0000000000400551 T unused
000000000040053c T used

unrelated.c

int unrelated(void)
{
    return 42;
}