From 30d28c558015afe22822647cc3943e2afb14afde Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Mon, 30 Nov 2015 12:07:33 +0100
Subject: 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.
---
 src/change_log.cc | 47 +++++++++++++----------------------------------
 1 file changed, 13 insertions(+), 34 deletions(-)

(limited to 'src/change_log.cc')

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);
 }
-- 
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