Make

GNU Make

Purpose

Guide agents through idiomatic Makefile patterns for C/C++ projects: phony targets, pattern rules, automatic dependency generation, and common build idioms.

Triggers

• "How do I write a Makefile for my C project?"
• "My Makefile rebuilds everything every time"
• "How do I add dependency tracking to Make?"
• "What does $@, `$ $@

### 4. Common Make patterns

#### Debug and release builds

```makefile
BUILD ?= release

ifeq ($(BUILD),debug)
  CFLAGS += -g -Og -DDEBUG
else
  CFLAGS += -O2 -DNDEBUG
endif

Usage: make BUILD=debug

Parallel builds

make -j$(nproc)     # use all CPUs
make -j4            # exactly 4 jobs

Add -Otarget (or -O) for ordered output: make -j$(nproc) -O

Verbose output

# In Makefile: suppress with @
build/%.o: src/%.c | build
	@echo "  CC  $<"
	@$(CC) $(CFLAGS) -c -o $@ $<

Override silence: make V=1 if you guard with $(V):

Q := $(if $(V),,@)
build/%.o: src/%.c
	$(Q)$(CC) $(CFLAGS) -c -o $@ $<

Installing

PREFIX ?= /usr/local

install: $(TARGET)
	install -d $(DESTDIR)$(PREFIX)/bin
	install -m 0755 $(TARGET) $(DESTDIR)$(PREFIX)/bin/

5. Multi-directory projects

For medium projects, avoid recursive make (fragile, slow). Use a flat Makefile that includes sub-makefiles:

# project/Makefile
include lib/module.mk
include src/app.mk

# lib/module.mk
LIB_SRCS := $(wildcard lib/*.c)
LIB_OBJS := $(LIB_SRCS:lib/%.c=build/lib_%.o)
OBJS      += $(LIB_OBJS)

build/lib_%.o: lib/%.c
	$(CC) $(CFLAGS) -c -o $@ $<

6. Common errors

| Error | Cause | Fix | |-------|-------|-----| | No rule to make target 'foo.o' | Missing source or rule | Check source path and pattern rule | | Nothing to be done for 'all' | Targets up to date | Touch a source file or run make clean | | Circular dependency dropped | Target depends on itself | Check dependency chain | | missing separator | Tab vs spaces | Recipes must use a tab, not spaces | | *** multiple target patterns | Pattern rule syntax error | Check % placement | | Rebuilds everything every time | Timestamps wrong, or PHONY missing | Check date; ensure all is .PHONY | | Header change not detected | No dep tracking | Add -MMD -MP and -include $(DEPS) |

For a full variable and function reference, see [references/cheatsheet.md](references/cheatsheet.md).

Related skills

• Use skills/build-systems/cmake for CMake-based projects
• Use skills/build-systems/ninja for Ninja as a make backend
• Use skills/compilers/gcc for CFLAGS details

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: mohitmishra786
• Source: mohitmishra786/low-level-dev-skills
• License: MIT
• Homepage: https://www.lowleveldevskills.com

Install and usage instructions live in the source repository linked above.