The Build Workflow

The commands

gcc -std=c23 -Wall -Wextra -c mathutil.c -o mathutil.o    # compile only
gcc -std=c23 main.c mathutil.o -o app                      # link
gcc -std=c23 -Wall -Wextra main.c mathutil.c -o app        # both at once

-c stops after compiling (object file, no linking). The final command compiles AND links in one step — fine while projects are small.

The flag vocabulary

| flag | meaning | |------|---------| | -std=c23 | which C standard to enforce | | -Wall -Wextra | the warning level this course assumes | | -Werror | warnings become errors (CI builds) | | -O2 | optimize for speed (shipping) | | -g | embed debug info (for gdb) | | -Iinclude | add a header search path | | -lm | link the math library |

Debug build: -g (plus sanitizers on glibc). Release build: -O2 -DNDEBUG. Never ship what you have not also built with warnings on.

Make in one screen

app: main.o mathutil.o
	gcc main.o mathutil.o -o app

main.o: main.c mathutil.h
	gcc -std=c23 -Wall -Wextra -c main.c

mathutil.o: mathutil.c mathutil.h
	gcc -std=c23 -Wall -Wextra -c mathutil.c

Make rebuilds only what changed — the dependency graph is the Makefile. Tab indentation is mandatory and famously unforgiving.