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C++ Build Process

  • C++ (based on C) is a mid-level compiled language.
  • Compiled language : It means the source code goes through a couple of steps to finally create the binary executable.

[*] Steps

Note : The below mentioned steps and examples are specifically for GNU gcc, though most other compilers follow the same process.

  • In the above image, their is a BlackBox, these steps will goes through explaining the internals of it :

1. Pre-processing : In the first phase , all the #includes , macros , conditional compilation basically all the statements that begin with # are processed i.e the pre-processor replaces that particular line with the actual content of the line.

$ cat example.cpp
#include<iostream>

#define a 5

int main()
{
  std::cout<<"Macro a is : " << a<<std::endl;
}

$ cpp example.cpp > example.i
# 'cpp' is the name of the pre-processsor , it line by line replaces the '#' with their actual definitions.

# example.i file contains the pre-processed code and contains the expanded source code.

2. Compiling : In the compilation phase, the compiler compiles the pre-processed source code into assembly code for a specific processor.

$ g++ -S example.i -o example.s
# The compiler creates the assembly code, for the processor of the machine the compiler is running on.

3. Assembly : In this phase, The assembler converts the assembly code(example.s) into machine code in the object file example.o.

$ as -o example.o example.s
# Thus the compiled and assembled 'object' file is ready now.

4. Linking : In the final linking phase, the linker links the diff object files together with the library code to produce an executable file "example".

$ ld  -o example example.o `other required libraries here`

# The final executable is produced here.

[*] C++ add-ons

  • The build process and steps that we discussed above are same for C, rather they are of C only and C++ was designed to be compatible with them.

  • Primary thing

    1. templates
    2. Name mangling
    3. Function over-loading, covered in mangling

Ques: Do you remember that there was no concept of function overloading in C, then how did C++ have it (since it is based on C only)? Ans : Name Mangling i.e it simply replaces the name internally.

[*] References/Resources