compilers 🗃️

compilers are programs that convert program source code to executable form

“executable” = machine code / bytecode

the Gnu C compiler: gcc — three steps in the compiling process

gcc -o file1.c file2.c

1. applies source-to-source transformation (pre-processor)
   • replaces constants created using #define — outputs something similar to C (.e file)
   • gcc -E file.c > file.e
2. compiles source code to produce object files
   • converts pre-processed file into machine code — outputs basically gibberish (.o file)
   • gcc -c file.c
3. links object files and libraries to produce executables
   • links files that depend on each other (e.g. libraries and multi-file) — outputs executable
   • gcc -o file file1.o file2.o

• other flags

note: dcc and 3c are ‘wrappers’ around gcc

• more checking and more detailed/understandable error messages
• better run-time support (e.g. array bounds, use of dynamic memory)

makefiles ⏩

for large projects, compilation gets complex:

• need to run many commands (or long commands)

• we don’t need to necessarily recompile every single file if we have only changed some

  (only perform step 1 and step 2 on modified files → then link all the .o files)

makefiles are usually named Makefile and placed in same directory as everything else