RegJIT Makefile Management

Overview

Maintain clear and efficient Makefile for building RegJIT project, managing test targets, and handling LLVM integration.

When to Use

•Adding new test targets
•Changing build flags or compiler options
•Updating LLVM dependencies
•Optimizing build performance
•Documenting build procedures
•Setting up CI/CD integration

Makefile Structure

Essential Sections

1. Configuration

makefile

DEBUG_FLAGS := -g -O0
LLVM_CONFIG := /opt/homebrew/Cellar/llvm/19.1.7_1/bin/llvm-config
CXXFLAGS := $(DEBUG_FLAGS) -Wall -Wno-unknown-warning-option -std=c++17
CXXFLAGS += $(shell $(LLVM_CONFIG) --cxxflags)
LDFLAGS := $(shell $(LLVM_CONFIG) --ldflags)
LDLIBS := $(shell $(LLVM_CONFIG) --libs)

Purpose: Centralize build configuration

•Single source of truth for flags
•Dynamic LLVM configuration
•Easy cross-platform adaptation

2. File Variables

makefile

REGJIT_OBJ := src/regjit.o
REGJIT_SRC := src/regjit.cpp src/regjit.h

Purpose: Avoid duplication, improve maintainability

3. Phony Targets

makefile

.PHONY: all clean test test_all

Purpose: Distinguish logical targets from real files

4. Build Rules

makefile

%.o: %.cpp
	$(CXX) $(CXXFLAGS) -c $< -o $@

test_anchor: tests/test_anchor.cpp $(REGJIT_OBJ)
	$(CXX) $(CXXFLAGS) -I./src -o $@ $^ $(LDFLAGS) $(LDLIBS)

Purpose: Clear dependency management

Adding New Test Target

Template

makefile

test_new_feature: tests/test_new_feature.cpp $(REGJIT_OBJ)
	$(CXX) $(CXXFLAGS) -I./src -o $@ $^ $(LDFLAGS) $(LDLIBS)

Steps

•Create test file in tests/test_new_feature.cpp
•Add target to Makefile
•Update test_all dependency list
•Test: make test_new_feature && ./test_new_feature

Example: Adding anchor_quant_edge test

makefile

test_anchor_quant_edge: tests/test_anchor_quant_edge.cpp $(REGJIT_OBJ)
	$(CXX) $(CXXFLAGS) -I./src -o $@ $^ $(LDFLAGS) $(LDLIBS)

Then add to test_all:

makefile

test_all: test_anchor test_charclass test_quantifier test_anchor_quant_edge
	@echo "Running all tests in tests/ directory..."

Common Makefile Patterns

Implicit Rules (Pattern Matching)

makefile

# Compile all .cpp files to .o
%.o: %.cpp
	$(CXX) $(CXXFLAGS) -c $< -o $@

Benefit: Automatically applies to new files

Using Variables

makefile

# Good - reusable
test_anchor: tests/test_anchor.cpp $(REGJIT_OBJ)
	$(CXX) $(CXXFLAGS) -I./src -o $@ $^ $(LDFLAGS) $(LDLIBS)

# Bad - hardcoded, not maintainable
test_anchor: tests/test_anchor.cpp src/regjit.o
	c++ -g -O0 -Wall -std=c++17 tests/test_anchor.cpp src/regjit.o -o test_anchor

Dependency Tracking

makefile

# Object file depends on source files
src/regjit.o: src/regjit.cpp src/regjit.h
	$(CXX) $(CXXFLAGS) -c $< -o $@

# Test executable depends on test source and core object
test: test.cpp src/regjit.o
	$(CXX) $(CXXFLAGS) -I./src -o $@ $^ $(LDFLAGS) $(LDLIBS)

Variable Reference

Automatic Variables

Variable	Meaning
`$@`	Target name (e.g., test_anchor)
`$<`	First dependency (e.g., test_anchor.cpp)
`$^`	All dependencies
`$+`	All dependencies (with duplicates)

LLVM Variables

makefile

CXXFLAGS += $(shell $(LLVM_CONFIG) --cxxflags)
LDFLAGS := $(shell $(LLVM_CONFIG) --ldflags)
LDLIBS := $(shell $(LLVM_CONFIG) --libs)

Common Issues & Solutions

Issue: Rebuilding Everything Unnecessarily

Problem: Missing dependencies cause full rebuild Solution: List all file dependencies correctly

makefile

# WRONG - recompiles even if header doesn't change
test: test.cpp
	$(CXX) ... -o $@ $^

# RIGHT - recompiles only on actual changes
test: test.cpp src/regjit.o
	$(CXX) ... -o $@ $^ $(LDLIBS)

Issue: Hardcoded Paths Break on Different Systems

Problem: /usr/local/bin/llvm-config doesn't exist everywhere Solution: Use dynamic discovery

makefile

# WRONG
LLVM_CONFIG := /usr/local/bin/llvm-config

# GOOD - uses which to find it
LLVM_CONFIG := $(shell which llvm-config)

Issue: Phony Targets Treated as Files

Problem: make clean creates empty file named "clean" Solution: Declare phony targets

makefile

.PHONY: clean test all
clean:
	rm -f *.o test_* debug*

Issue: Parallel Build Fails

Problem: make -j4 breaks with incorrect dependencies Solution: Ensure all dependencies listed

makefile

# Good for parallel
test_anchor: tests/test_anchor.cpp $(REGJIT_OBJ)
test_charclass: tests/test_charclass.cpp $(REGJIT_OBJ)
# Can run in parallel without issues

Build Commands

Common Operations

bash

# Default build
make

# Specific test
make test_anchor

# All tests
make test_all

# Clean artifacts
make clean

# Rebuild everything
make clean && make

# Parallel build (4 cores)
make -j4

# Show what would be executed (dry run)
make -n test_anchor

# Debug dependencies
make -d test_anchor

Checking Makefile Correctness

bash

# Syntax check
make -n all    # Shows commands without executing

# Verify dependencies
make -d 2>&1 | grep "test_anchor"

# Clean rebuild
make clean && make test_all

Optimization Tips

1. Object File Caching

makefile

src/regjit.o: src/regjit.cpp src/regjit.h
	$(CXX) $(CXXFLAGS) -c $< -o $@

Benefits: Only recompile when source changes

2. Parallel Builds

bash

make -j4  # Use 4 cores

Speedup: 3-4x faster on multi-core machines

3. Conditional Compilation

makefile

ifdef DEBUG
    CXXFLAGS += -DDEBUG
endif

Usage: make DEBUG=1

Maintenance Checklist

Viewing Makefile

bash

# Show all targets
grep "^[a-z_]*:" Makefile

# Show variables
grep "^[A-Z_]* :=" Makefile

# Show dependencies for target
make -d test_anchor 2>&1 | grep "test_anchor"

Quick Reference

Command	Effect
`make`	Build default (all)
`make clean`	Remove artifacts
`make test_X`	Build test_X
`make -n`	Show commands (no execute)
`make -j N`	Parallel with N cores
`make -d`	Debug mode