Question

in c/c++ program:

1. The differences between symbol relocation and symbol resolution.

2. Why is it a good idea to have multiple object files as opposed to just one?

3.

Answer 1

1. Answer: Difference between Symbol relocation vs Symbol Resolution

Symbol resolution: Symbol resolution means to find the definition of undefined reference in an object file.

Ex: let say we have two file main.c and swapnumber.c

main.c   

int num[2] = {5,6};

int main(){

swapnumber();

}

The use of swapnumber() in main.o needs to be resolved to definition found in swapnumber.o

Symbol relocation: It is a process of assigning an absolute address to the code and data.

Ex: swapnumber.c

extern int num[];

void swapnumber(){

int temp;

temp = num[1];

int num[1] = num[0];

num[0] = temp;

}

here swapnumber.c compiled without knowing about num, it is the responsibility of the linker to allocate memory and update uses of num in swapnumber.o to use this location.

2. Answer: Multiple objects file optimize the performance of a compiler. The separate unit compilation is faster than a single object file. Let say we are working on a large project and we did a few changes in the code of the project than we need to compile the entire file and a new object file will be created. This makes the compiler slow. If we have multiple object files of a large project than if we change the code in one of the files, then it is easy to create an object of the smaller file rather than a whole project at once.