Simple build config with dependency tracking.

9 files changed, 268 insertions, 0 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..7cad9bd
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,11 @@
+all: libcppbuild.a cppbuild
+
+libcppbuild.a: libcppbuild.cc
+	g++ -g -std=c++17  libcppbuild.cc -c -o libcppbuild.o
+	ar rcs libcppbuild.a libcppbuild.o
+
+cppbuild: cppbuild.cc libcppbuild.a
+	g++ -g -std=c++17 cppbuild.cc libcppbuild.a -o cppbuild
+
+clean:
+	rm -f cppbuild libcppbuild.o libcppbuild.a
diff --git a/cppbuild.cc b/cppbuild.cc
new file mode 100644
index 0000000..b06b082
--- /dev/null
+++ b/cppbuild.cc
@@ -0,0 +1,19 @@
+#include <vector>
+#include <string>
+#include <utility>
+
+#include "libcppbuild.h"
+
+BuildConfiguration configs()
+{
+	return
+	{
+		// target
+		"bas",
+		{
+			// source files
+			"src/foo.cc",
+			"src/bar.cc",
+		}
+	};
+}
diff --git a/libcppbuild.cc b/libcppbuild.cc
new file mode 100644
index 0000000..ff208b3
--- /dev/null
+++ b/libcppbuild.cc
@@ -0,0 +1,204 @@
+#include <vector>
+#include <string>
+#include <filesystem>
+#include <iostream>
+#include <fstream>
+#include <regex>
+#include <utility>
+
+#include "libcppbuild.h"
+
+namespace
+{
+std::string readFile(const std::string &fileName)
+{
+	std::ifstream ifs(fileName.c_str(), std::ios::in | std::ios::binary | std::ios::ate);
+
+	std::ifstream::pos_type fileSize = ifs.tellg();
+	ifs.seekg(0, std::ios::beg);
+
+	std::vector<char> bytes(fileSize);
+	ifs.read(bytes.data(), fileSize);
+
+	return std::string(bytes.data(), fileSize);
+}
+
+std::vector<std::string> readDeps(const std::string& depFile)
+{
+	if(!std::filesystem::exists(depFile))
+	{
+		return {};
+	}
+
+	auto str = readFile(depFile);
+
+	std::vector<std::string> output;
+	std::string tmp;
+	bool start{false};
+	bool in_whitespace{false};
+	for(const auto& c : str)
+	{
+		if(c == '\\' || c == '\n')
+		{
+			continue;
+		}
+
+		if(c == ':')
+		{
+			start = true;
+			continue;
+		}
+
+		if(!start)
+		{
+			continue;
+		}
+
+		if(c == ' ' || c == '\t')
+		{
+			if(in_whitespace)
+			{
+				continue;
+			}
+
+			if(!tmp.empty())
+			{
+				output.push_back(tmp);
+			}
+			tmp.clear();
+			in_whitespace = true;
+		}
+		else
+		{
+			in_whitespace = false;
+			tmp += c;
+		}
+	}
+
+	if(!tmp.empty())
+	{
+		output.push_back(tmp);
+	}
+
+	return output;
+}
+} // namespace ::
+
+
+
+int main(int argc, const char* argv[])
+{
+	if(argc == 2 && std::string(argv[1]) == "clean")
+	{
+		system("rm -Rf build");
+		return 0;
+	}
+
+	std::filesystem::path builddir("build/");
+	std::filesystem::create_directory(builddir);
+
+	auto project = configs();
+	std::string output = "build/" + project.target;
+	const auto& files = project.sources;
+	std::vector<std::string> objects;
+
+	std::cout << "Building\n";
+	for(const auto& file : files)
+	{
+		auto path = std::filesystem::path(file);
+		std::string object = builddir / path.stem();
+		object += ".o";
+		objects.push_back(object);
+
+		std::string deps = builddir / path.stem();
+		deps += ".d";
+
+		if(!std::filesystem::exists(file))
+		{
+			std::cout << "Missing source file: " << file << "\n";
+			return 1;
+		}
+
+		bool recompile{false};
+
+		if(!std::filesystem::exists(object) ||
+		   !std::filesystem::exists(deps))
+		{
+			recompile = true;
+		}
+
+		if(!recompile &&
+		   std::filesystem::last_write_time(file) >
+		   std::filesystem::last_write_time(deps))
+		{
+			recompile = true;
+		}
+
+		if(!recompile)
+		{
+			auto depList = readDeps(deps);
+			for(const auto& dep : depList)
+			{
+				if(!std::filesystem::exists(dep) ||
+				   std::filesystem::last_write_time(object) <
+				   std::filesystem::last_write_time(dep))
+				{
+					recompile = true;
+					break;
+				}
+			}
+		}
+
+		if(recompile ||
+		   !std::filesystem::exists(object) ||
+		   std::filesystem::last_write_time(file) >
+		   std::filesystem::last_write_time(object))
+		{
+			std::string compiler = "g++ -MMD -c " + file + " -o " + object;
+			std::cout << compiler << "\n";
+			if(system(compiler.data()))
+			{
+				return 1;
+			}
+		}
+	}
+
+	std::cout << "Linking\n";
+	bool dolink{false};
+	if(!std::filesystem::exists(output))
+	{
+		dolink = true;
+	}
+	else
+	{
+		for(const auto& object : objects)
+		{
+			if(std::filesystem::last_write_time(output) <=
+			   std::filesystem::last_write_time(object))
+			{
+				dolink = true;
+				break;
+			}
+		}
+	}
+
+	if(!dolink)
+	{
+		std::cout << "No linking needed\n";
+		return 0;
+	}
+
+	std::string objectlist;
+	for(const auto& object : objects)
+	{
+		objectlist += object + " ";
+	}
+	std::string compiler = "g++ " + objectlist + " -o " + output;
+	std::cout << compiler << "\n";
+	if(system(compiler.data()))
+	{
+		return 1;
+	}
+
+	return 0;
+}
diff --git a/libcppbuild.h b/libcppbuild.h
new file mode 100644
index 0000000..11a8eb7
--- /dev/null
+++ b/libcppbuild.h
@@ -0,0 +1,12 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+struct BuildConfiguration
+{
+	std::string target;
+	std::vector<std::string> sources;
+};
+
+BuildConfiguration configs();
diff --git a/src/bar.cc b/src/bar.cc
new file mode 100644
index 0000000..2486a0a
--- /dev/null
+++ b/src/bar.cc
@@ -0,0 +1,9 @@
+#include <iostream>
+
+#include "foo.h"
+
+int main()
+{
+	foo();
+	std::cout << __FILE__ << "\n";
+}
diff --git a/src/bar.o b/src/bar.o
new file mode 100644
index 0000000..37903db
--- /dev/null
+++ b/src/bar.o
diff --git a/src/bas.h b/src/bas.h
new file mode 100644
index 0000000..3f59c93
--- /dev/null
+++ b/src/bas.h
@@ -0,0 +1,2 @@
+#pragma once
+
diff --git a/src/foo.cc b/src/foo.cc
new file mode 100644
index 0000000..b2c478c
--- /dev/null
+++ b/src/foo.cc
@@ -0,0 +1,6 @@
+#include <iostream>
+
+void foo()
+{
+	std::cout << __FILE__ << "\n";
+}
diff --git a/src/foo.h b/src/foo.h
new file mode 100644
index 0000000..9620fc7
--- /dev/null
+++ b/src/foo.h
@@ -0,0 +1,5 @@
+#pragma once
+
+#include "bas.h"
+
+void foo();