Summary - Linker

Combine object files, relocation and ELF to write a symbol viewer.

Summary - Symbol viewer

In this lesson you'll combine object files, relocation and ELF to write a symbol viewer. The program defines three functions, prints each one's name, gives the total count, and finally calls one to show its result.

Each function is a symbol: the linker records them in the symbol table. Printing the function names is like listing the symbol table contents. The call shows symbol resolution and relocation logic at run time. This exercise merges the linker topics in one program.

Exercise Write a symbol viewer

Define three functions: int add(int a, int b) { return a + b; }, int sub(int a, int b) { return a - b; }, int mul(int a, int b) { return a * b; }. Write int main(void); print each function's name as printf("Sembol: add\n") (for all three), then call printf("Toplam: 3\n") and printf("Çağrı: %d\n", add(40, 2)).

Show example solution

#include <stdio.h>

int add(int a, int b) { return a + b; }
int sub(int a, int b) { return a - b; }
int mul(int a, int b) { return a * b; }

int main(void) {
    printf("Sembol: add\n");
    printf("Sembol: sub\n");
    printf("Sembol: mul\n");
    printf("Toplam: 3\n");
    printf("Çağrı: %d\n", add(40, 2));
    return 0;
}

Test yourself

What does a symbol viewer show?
- Only error codes
- Only memory addresses
- Only compiler versions
- Function and variable names
Show answer

Function and variable names — A symbol viewer lists names from the symbol table.

Complete the function call

int add(int a, int b) { return a + b; }
int result = add(40, ____);

Show answer

int add(int a, int b) { return a + b; }
int result = add(40, 2);

Match concept to role

Object file

Relocatable
Symbol

Name and address
Relocation

Address patching
ELF

File format

Next lesson: What is embedded?

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