Extract actual function acquisition

The pointers to the actual function implementations are now fetched inside the `actual` namespace declared in the `actual_function.h` header.

Fixed source of _noreturn_ related warning during compilation by adding the appropriate flag. Sadly this means that we can not use `std::function` in this context as it doesn't seem to carry these _c-like_ flags.

4 files changed, 79 insertions, 40 deletions

diff --git a/src/actual_function.h b/src/actual_function.h
new file mode 100644
index 0000000..0ffe0c2
--- /dev/null
+++ b/src/actual_function.h
@@ -0,0 +1,60 @@
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#ifndef CHANGE_SRC_ACTUAL_FUNCTION_H_
+#define CHANGE_SRC_ACTUAL_FUNCTION_H_
+
+#include <dlfcn.h>
+#include <sys/mman.h>
+
+#include <memory>
+#include <cstring>
+
+namespace {
+	template <class Result, typename... Arguments>
+	std::function<Result(Arguments...)> get_actual_function(
+		const std::string& symbol_name) {
+
+		Result (*real_function)(Arguments...) = nullptr;
+		const void* symbol_address = dlsym(RTLD_NEXT, symbol_name.c_str());
+
+		std::memcpy(&real_function, &symbol_address, sizeof(symbol_address));
+
+		return std::function<Result(Arguments...)>(real_function);
+	}
+}
+
+namespace actual {
+	static auto write = get_actual_function<
+		ssize_t,
+		int, const void*, size_t
+	>("write");
+
+	static auto rename = get_actual_function<
+		int,
+		const char*, const char*
+	>("rename");
+
+	static auto rmdir = get_actual_function<
+		int,
+		const char*
+	>("rmdir");
+
+	static auto unlink = get_actual_function<
+		int,
+		const char*
+	>("unlink");
+
+	static auto unlinkat = get_actual_function<
+		int,
+		int, const char*, int
+	>("unlinkat");
+
+	static auto mmap = get_actual_function<
+		void*,
+		void*, size_t, int, int, int, off_t
+	>("mmap");
+}
+
+#endif  // CHANGE_SRC_ACTUAL_FUNCTION_H_
diff --git a/src/change_log.cc b/src/change_log.cc
index f07296e..8ff1475 100644
--- a/src/change_log.cc
+++ b/src/change_log.cc
@@ -2,32 +2,18 @@
 #define _GNU_SOURCE
 #endif
 
-#include <sys/mman.h>
-
-#include <memory>
 #include <algorithm>
 #include <functional>
 #include <unordered_set>
 
 #include "io.h"
 #include "utility.h"
+#include "actual_function.h"
 
 static std::unique_ptr<std::unordered_set<std::string>> tracked_files;
 static std::unique_ptr<io::FileDescriptorGuard>         fd_guard;
 static std::unique_ptr<utility::Logger>                 logger;
 
-template <class Result, typename... Arguments>
-std::function<Result(Arguments...)> get_real_function(
-	const std::string& symbol_name) {
-
-	Result (*real_function)(Arguments...) = nullptr;
-	const void* symbol_address = dlsym(RTLD_NEXT, symbol_name.c_str());
-
-	std::memcpy(&real_function, &symbol_address, sizeof(symbol_address));
-
-	return std::function<Result(Arguments...)>(real_function);
-}
-
 void init() __attribute__ ((constructor));
 void init() {
 	tracked_files = std::make_unique<std::unordered_set<std::string>>();
@@ -43,9 +29,14 @@ void init() {
 }
 
 void exit(int status) {
+	__attribute__((__noreturn__)) void(*real_exit)(int) = nullptr;
+	const void* symbol_address = dlsym(RTLD_NEXT, "exit");
+
+	std::memcpy(&real_exit, &symbol_address, sizeof(symbol_address));
+
 	logger->append("exit");
 
-	get_real_function<void, int>("exit")(status);
+	real_exit(status);
 }
 
 bool is_tracked_file(const std::string& file_name) {
@@ -57,8 +48,6 @@ bool track_file(const std::string& file_name) {
 }
 
 ssize_t write(int fd, const void* buffer, size_t count) {
-	static auto real_write = get_real_function<ssize_t, int, const void*, size_t>("write");
-
 	if ( io::is_regular_file(fd) ) {
 		const std::string file_name{ io::get_file_name(fd) };
 
@@ -69,52 +58,42 @@ ssize_t write(int fd, const void* buffer, size_t count) {
 		}
 	}
 
-	return real_write(fd, buffer, count);
+	return actual::write(fd, buffer, count);
 }
 
 int rename(const char* old_path, const char* new_path) {
-	static auto real_rename = get_real_function<int, const char*, const char*>("rename");
-
 	if ( !is_tracked_file(old_path) ) {
 		track_file(old_path);
 	}
 
 	logger->append("renamed '" + std::string(old_path) + "' to '" + std::string(new_path) + "'");
 
-	return real_rename(old_path, new_path);
+	return actual::rename(old_path, new_path);
 }
 
 int rmdir(const char* path) {
-	static auto real_rmdir = get_real_function<int, const char*>("rmdir");
-
 	logger->append("removed directory '" + std::string(path) + "'");
 
-	return real_rmdir(path);
+	return actual::rmdir(path);
 }
 
 int unlink(const char* path) {
-	static auto real_unlink = get_real_function<int, const char*>("unlink");
-
 	logger->append("removed '" + std::string(path) + "'");
 
-	return real_unlink(path);
+	return actual::unlink(path);
 }
 
 int unlinkat(int dirfd, const char* path, int flags) {
-	static auto real_unlinkat = get_real_function<int, int, const char*, int>("unlinkat");
-
 	if ( dirfd == AT_FDCWD ) {
 		logger->append("removed '" + std::string(path) + "'");
 	} else {
 		logger->append("removed '" + io::get_file_name(dirfd) + path + "'");
 	}
 
-	return real_unlinkat(dirfd, path, flags);
+	return actual::unlinkat(dirfd, path, flags);
 }
 
 void* mmap(void* addr, size_t length, int prot, int flags, int fd, off_t offset) {
-	static auto real_mmap = get_real_function<void*, void*, size_t, int, int, int, off_t>("mmap");
-
 	if ( ( prot & PROT_WRITE ) && io::is_regular_file(fd) ) {
 		const std::string file_name{ io::get_file_name(fd) };
 
@@ -125,5 +104,5 @@ void* mmap(void* addr, size_t length, int prot, int flags, int fd, off_t offset)
 		}
 	}
 
-	return real_mmap(addr, length, prot, flags, fd, offset);
+	return actual::mmap(addr, length, prot, flags, fd, offset);
 }
diff --git a/src/io.h b/src/io.h
index c36a5b0..676ebac 100644
--- a/src/io.h
+++ b/src/io.h
@@ -1,5 +1,5 @@
-#ifndef CHANGE_IO_H_
-#define CHANGE_IO_H_
+#ifndef CHANGE_SRC_IO_H_
+#define CHANGE_SRC_IO_H_
 
 #include <unistd.h>
 #include <dlfcn.h>
@@ -58,4 +58,4 @@ bool is_regular_file(int fd) {
 
 }
 
-#endif  // CHANGE_IO_H_
+#endif  // CHANGE_SRC_IO_H_
diff --git a/src/utility.h b/src/utility.h
index 27ce8e9..96ee15c 100644
--- a/src/utility.h
+++ b/src/utility.h
@@ -1,5 +1,5 @@
-#ifndef CHANGE_UTILITY_H_
-#define CHANGE_UTILITY_H_
+#ifndef CHANGE_SRC_UTILITY_H_
+#define CHANGE_SRC_UTILITY_H_
 
 #include <ext/stdio_filebuf.h>
 
@@ -25,4 +25,4 @@ class Logger {
 
 }
 
-#endif  // CHANGE_UTILITY_H_
+#endif  // CHANGE_SRC_UTILITY_H_