What are the stages a C program goes through from source code to executable?

Question

Accepted Answer

Compile each .c to assembly, assemble that to a .o object file, then link all the objects plus the C runtime into one executable.

* Each source file travels its own compile → assemble path to a .o; the linker fuses all objects plus the C runtime into the final executable. *
The compilation pipeline:

Stage
Tool
Input
Output

1. Compilation
cc1/cpp
.c file
.s (assembly)

2. Assembly
as
.s file
.o (relocatable object)

3. Linking
ld/collect2
.o files + libraries
executable

Key insight: Each .c file is compiled independently to its own .o file. The linker combines all .o files plus the C runtime library (CRT) into the final executable.
# View the full compilation process
$ gcc -v -O2 -Wall -g -o prog main.c swap.c

Tip: GCC is actually a "compiler driver" - it orchestrates calls to the preprocessor, compiler, assembler, and linker.
Go deeper:

GCC — the compiler driver (Wikipedia) — how one gcc command chains preprocessor, compiler, assembler and linker.
 Ian Lance Taylor — Linkers, part 1 — start of a linker author's classic 20-part deep dive into what happens after compilation.

Stage	Tool	Input	Output
1. Compilation	cc1/cpp	`.c` file	`.s` (assembly)
2. Assembly	as	`.s` file	`.o` (relocatable object)
3. Linking	ld/collect2	`.o` files + libraries	executable