bajia/configure.py

#!/usr/bin/env python3
"""generates a Ninja build file

usage:
    python3 configure.py
    python3 configure.py --asan      # enable address/undefined sanitizers
    python3 configure.py --debug     # -O0 instead of -O2
"""
import argparse
import os
import shutil
import sys
from pathlib import Path

ROOT = Path(__file__).resolve().parent
SRC = ROOT / "src"
BUILD = ROOT / "build"

CXX = os.environ.get("CXX", "g++")
CXXFLAGS = ["-std=c++20", "-O2", "-g"]
WARNINGS = ["-Wall", "-Wextra", "-Wpedantic", "-Wshadow", "-Wconversion", "-Wnull-dereference"]
linkflags = []

def discover_sources():
    return sorted(
        p.name for p in SRC.glob("*.cpp")
        if not p.name.endswith("_main.cpp") and not p.name.startswith(".")
    )

def write_makefile_convenience():
    make = ROOT / "Makefile"
    make.write_text(
        """# convenience wrapper around configure.py + ninja.
#
#   make            -> configure + build
#   make configure  -> regenerate build.ninja
#   make clean      -> remove build dir
#   make format     -> clang-format all sources (if available)
#
.PHONY: all configure clean format
all: configure
\t@ninja -C build

configure:
\t@python3 configure.py

clean:
\t@rm -rf build

format:
\t@command -v clang-format >/dev/null && clang-format -i src/*.cpp src/*.hpp || true
""",
        encoding="utf-8",
    )


def emit_ninja(cxx, cxxflags, dst):
    sources = discover_sources()
    objs = ["obj/" + Path(s).stem + ".o" for s in sources]
    target = "bajia"

    rule_cxx = (
        "rule cxx\n"
        "  command = {cxx} {cxxflags} -MMD -MF $out.d -c $in -o $out\n"
        "  depfile = $out.d\n"
        "  deps = gcc\n"
        "  description = CXX $out\n"
    ).format(cxx=cxx, cxxflags=" ".join(cxxflags))

    rule_link = (
        "rule link\n"
        "  command = {cxx} {ldflags} $in -o $out -lpthread\n"
        "  description = LINK $out\n"
    ).format(cxx=cxx, ldflags=" ".join(linkflags))

    lines = ["# generated by configure.py -- do not edit", "ninja_required_version = 1.8", ""]
    lines.append(rule_cxx)
    lines.append(rule_link)
    lines.append('build {target}: link {objs}'.format(target=target, objs=" ".join(objs)))
    lines.append("")
    for o, s in zip(objs, sources):
        lines.append('build {o}: cxx {src}/{s}'.format(o=o, src=SRC, s=s))
    lines.append("")
    lines.append('build all: phony {target}'.format(target=target))
    lines.append("default all")
    lines.append("")

    (BUILD / "obj").mkdir(exist_ok=True)
    dst.write_text("\n".join(lines) + "\n", encoding="utf-8")

def parse_args():
    p = argparse.ArgumentParser(description="Configure bajia build (generates build.ninja)")
    p.add_argument("--asan", action="store_true", help="enable address + UB sanitizers")
    p.add_argument("--debug", action="store_true", help="disable -O2, enable -O0")
    p.add_argument("--clean", action="store_true", help="remove build dir")
    return p.parse_args()

def main():
    args = parse_args()
    if args.clean:
        shutil.rmtree(BUILD, ignore_errors=True)
        print("removed build/")
        return 0

    if not shutil.which("ninja"):
        print("error: ninja not found in PATH", file=sys.stderr)
        return 1

    BUILD.mkdir(exist_ok=True)

    cxxflags = list(CXXFLAGS)
    global linkflags
    linkflags = []
    if args.debug:
        cxxflags = [f for f in cxxflags if f != "-O2"]
        cxxflags += ["-O0"]
    if args.asan:
        cxxflags += ["-fsanitize=address,undefined", "-fno-omit-frame-pointer"]
        linkflags += ["-fsanitize=address,undefined"]

    cxxflags = [f for f in cxxflags if f not in WARNINGS]
    cxxflags = WARNINGS + cxxflags

    emit_ninja(CXX, cxxflags, BUILD / "build.ninja")
    write_makefile_convenience()

    print(f"configured {len(discover_sources())} sources -> build/build.ninja")
    print("run: ninja -C build")
    return 0

if __name__ == "__main__":
    sys.exit(main())