From f4eb3c80e63b5323dbb19b1103ba1db2dd1c4c41 Mon Sep 17 00:00:00 2001
From: Bent Bisballe Nyeng <deva@aasimon.org>
Date: Tue, 15 Jun 2021 18:44:14 +0200
Subject: Recompile affected files if compiler flags change in build
 configuration.

---
 task_cc.cc | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-------
 task_cc.h  |  5 +++++
 2 files changed, 72 insertions(+), 8 deletions(-)

diff --git a/task_cc.cc b/task_cc.cc
index 34129a3..bef108e 100644
--- a/task_cc.cc
+++ b/task_cc.cc
@@ -89,10 +89,15 @@ TaskCC::TaskCC(const BuildConfiguration& config, const Settings& settings,
 	, settings(settings)
 {
 	sourceFile = source;
+
 	targetFile = settings.builddir / sourceFile.stem();
 	targetFile += ".o";
+
 	depsFile = settings.builddir / sourceFile.stem();
 	depsFile += ".d";
+
+	flagsFile = settings.builddir / sourceFile.stem();
+	flagsFile += ".flags";
 }
 
 bool TaskCC::dirty()
@@ -115,6 +120,12 @@ bool TaskCC::dirty()
 		return true;
 	}
 
+	if(!std::filesystem::exists(flagsFile))
+	{
+		//std::cout << "Missing flagsFile\n";
+		return true;
+	}
+
 	if(std::filesystem::last_write_time(sourceFile) >
 	   std::filesystem::last_write_time(depsFile))
 	{
@@ -122,6 +133,15 @@ bool TaskCC::dirty()
 		return true;
 	}
 
+	{
+		auto lastFlags = readFile(flagsFile);
+		if(flagsString() != lastFlags)
+		{
+			//std::cout << "The compiler flags changed\n";
+			return true;
+		}
+	}
+
 	auto depList = readDeps(depsFile);
 	for(const auto& dep : depList)
 	{
@@ -152,13 +172,9 @@ int TaskCC::run()
 		return 1;
 	}
 
-	std::string comp = "/usr/bin/g++";
-	auto flags = config.cxxflags;
-	if(std::string(sourceFile.extension()) == ".c")
-	{
-		comp = "/usr/bin/gcc";
-		flags = config.cflags;
-	}
+	std::string comp = compiler();
+	auto compiler_flags = flags();
+
 	std::vector<std::string> args;
 	args.push_back("-MMD");
 	args.push_back("-c");
@@ -166,11 +182,16 @@ int TaskCC::run()
 	args.push_back("-o");
 	args.push_back(std::string(targetFile));
 
-	for(const auto& flag : flags)
+	for(const auto& flag : compiler_flags)
 	{
 		args.push_back(flag);
 	}
 
+	{ // Write flags to file.
+		std::ofstream flagsStream(flagsFile);
+		flagsStream << flagsString();
+	}
+
 	return execute(comp, args);
 }
 
@@ -188,6 +209,12 @@ int TaskCC::clean()
 		std::filesystem::remove(depsFile);
 	}
 
+	if(std::filesystem::exists(flagsFile))
+	{
+		std::cout << "Removing " << std::string(flagsFile) << "\n";
+		std::filesystem::remove(flagsFile);
+	}
+
 	return 0;
 }
 
@@ -200,3 +227,35 @@ std::string TaskCC::target() const
 {
 	return targetFile;
 }
+
+std::vector<std::string> TaskCC::flags() const
+{
+	if(std::string(sourceFile.extension()) == ".c")
+	{
+		return config.cflags;
+	}
+	return config.cxxflags;
+}
+
+std::string TaskCC::flagsString() const
+{
+	std::string flagsStr;
+	for(const auto& flag : flags())
+	{
+		if(!flagsStr.empty())
+		{
+			flagsStr += " ";
+		}
+		flagsStr += flag;
+	}
+	return flagsStr;
+}
+
+std::string TaskCC::compiler() const
+{
+	if(std::string(sourceFile.extension()) == ".c")
+	{
+		return "/usr/bin/gcc";
+	}
+	return "/usr/bin/g++";
+}
diff --git a/task_cc.h b/task_cc.h
index c73a1e5..5c19017 100644
--- a/task_cc.h
+++ b/task_cc.h
@@ -29,9 +29,14 @@ public:
 	std::string target() const override;
 
 private:
+	std::vector<std::string> flags() const;
+	std::string flagsString() const;
+	std::string compiler() const;
+
 	std::filesystem::path sourceFile;
 	std::filesystem::path targetFile;
 	std::filesystem::path depsFile;
+	std::filesystem::path flagsFile;
 
 	const BuildConfiguration& config;
 	const Settings& settings;
-- 
cgit v1.2.3