From 9fe6626a63718635cca6ce8920e1669d099d46a7 Mon Sep 17 00:00:00 2001
From: Bent Bisballe Nyeng <deva@aasimon.org>
Date: Sat, 19 Jun 2021 11:58:12 +0200
Subject: Make self-aware (and recompile/re-launch as needed)

---
 .gitignore     |  4 +++-
 Makefile       |  8 ++++++--
 cppbuild.cc    | 30 ++++++++++++++++++++++++++++++
 execute.cc     |  8 ++++++++
 libcppbuild.cc | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 libcppbuild.h  |  3 +++
 6 files changed, 103 insertions(+), 3 deletions(-)

diff --git a/.gitignore b/.gitignore
index e518938..7d69636 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
+drumgizmo/
+build/
 cppbuild
 *.a
-*.o
\ No newline at end of file
+*.o
diff --git a/Makefile b/Makefile
index af29818..507d841 100644
--- a/Makefile
+++ b/Makefile
@@ -1,10 +1,11 @@
-all: libcppbuild.a
+all: libcppbuild.a cppbuild
 
 SRC = \
 	libcppbuild.cc \
 	task_cc.cc \
 	task_ld.cc \
 	task_ar.cc \
+	task_so.cc \
 	task.cc \
 	execute.cc \
 
@@ -18,5 +19,8 @@ CXXFLAGS = -g -O3 -std=c++17 -I.
 libcppbuild.a: $(OBJ)
 	ar rcs $@ $(OBJ)
 
+cppbuild: cppbuild.cc libcppbuild.a
+	g++ $(CXXFLAGS) -pthread cppbuild.cc libcppbuild.a -o $@
+
 clean:
-	rm -f libcppbuild.a $(OBJ)
+	rm -f libcppbuild.a $(OBJ) cppbuild
diff --git a/cppbuild.cc b/cppbuild.cc
index 882fe63..b1b31ed 100644
--- a/cppbuild.cc
+++ b/cppbuild.cc
@@ -18,8 +18,38 @@ exit $?
 
 #include "libcppbuild.h"
 
+/*
+Nested build configurations for for example unit-tests in a test folder
+#include "test/cppbuild.cc"
+*/
+
 std::vector<BuildConfiguration> configs()
 {
+	reg(__FILE__);
+/*
+Glob convenience methods
+std::string glob = getFilesInDir(...);
+*/
+
+/*
+Compilation database
+https://clang.llvm.org/docs/JSONCompilationDatabase.html
+*/
+
+/*
+En feature mere kunne være: pre-post build hooks
+De vil kunne udtrykkes som intra-build dependencies
+Og så selvfølgelig med conditions
+*/
+
+/*
+Target som er "shell script" eller sådan noget
+så kan man kalde f.eks. imageconvert
+*/
+
+/*
+Compiler selection per-target (for arm cross-compilation)
+*/
 	return
 	{
 		{
diff --git a/execute.cc b/execute.cc
index cb96bc5..bb691cf 100644
--- a/execute.cc
+++ b/execute.cc
@@ -7,6 +7,14 @@
 #include <spawn.h>
 #include <iostream>
 
+/*
+https://blog.famzah.net/2009/11/20/a-much-faster-popen-and-system-implementation-for-linux/
+https://github.com/famzah/popen-noshell/commit/1f9eaf4eeef348d1efe0f3c7fe8ab670653cfbb1
+https://blog.famzah.net/2018/12/19/posix_spawn-performance-benchmarks-and-usage-examples/
+https://stackoverflow.com/questions/4259629/what-is-the-difference-between-fork-and-vfork/5207945#5207945
+ */
+
+
 namespace
 {
 int parent_waitpid(pid_t pid)
diff --git a/libcppbuild.cc b/libcppbuild.cc
index 69d23ba..b400061 100644
--- a/libcppbuild.cc
+++ b/libcppbuild.cc
@@ -18,6 +18,7 @@
 #include "task_ar.h"
 #include "task_so.h"
 #include "settings.h"
+#include "execute.h"
 
 #include <unistd.h>
 
@@ -82,8 +83,60 @@ std::shared_ptr<Task> getNextTask(const std::list<std::shared_ptr<Task>>& allTas
 	return nullptr;
 }
 
+namespace
+{
+// Hack to get command-line args for re-launch
+int g_argc;
+char** g_argv;
+}
+
+// TODO: Use c++20 when ready, somehing like this:
+//void reg(const std::source_location location =
+//         std::source_location::current())
+void reg(const std::string& location)
+{
+	std::filesystem::path configFile(location);
+	std::filesystem::path binFile(configFile.stem());
+	if(std::filesystem::last_write_time(binFile) <=
+	   std::filesystem::last_write_time(configFile))
+	{
+		std::cout << "Rebuilding config\n";
+		auto ret = execute("/usr/bin/g++",
+		                   {
+			                   "-s",
+			                   "-O3",
+			                   "-std=c++17",
+			                   "-pthread",
+			                   configFile.string(),
+			                   "libcppbuild.a",
+			                   "-o",
+			                   binFile.string(),
+			                 });
+		if(ret != 0)
+		{
+			std::cerr << "Failed.\n";
+			exit(1);
+		}
+		else
+		{
+			std::cout << "Re-launch\n";
+			std::vector<std::string> args;
+			for(int i = 1; i < g_argc; ++i)
+			{
+				args.push_back(g_argv[i]);
+			}
+			exit(execute(g_argv[0], args));
+		}
+	}
+
+//	g++ -s -O3 -std=c++17 -pthread $0 libcppbuild.a -o cppbuild
+}
+
 int main(int argc, char* argv[])
 {
+	g_argc = argc;
+	g_argv = argv;
+
 	Settings settings;
 	// TODO: Set from commandline
 	settings.builddir = "build/foo";
diff --git a/libcppbuild.h b/libcppbuild.h
index 50b4459..98f6716 100644
--- a/libcppbuild.h
+++ b/libcppbuild.h
@@ -3,6 +3,7 @@
 
 #include <string>
 #include <vector>
+//#include <source_location>
 
 struct BuildConfiguration
 {
@@ -15,3 +16,5 @@ struct BuildConfiguration
 };
 
 std::vector<BuildConfiguration> configs();
+
+void reg(const std::string& location);
-- 
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