From 7582ab165b4c57d2325561b59d99a6665af28cc3 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Thu, 11 Feb 2016 18:43:27 +0100
Subject: Delay tracking activation

Introduce global static `enabled` variable used to signal the interposed functions to either start tracking or perform plain forwarding without any additional logic.
This is required as e.g. `nvim` crashed when wrapped in `libChangeLog` because it called interposed functions during library initialization.
---
 src/change_log.cc | 65 +++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 21 deletions(-)

diff --git a/src/change_log.cc b/src/change_log.cc
index a6f1437..8ff99e4 100644
--- a/src/change_log.cc
+++ b/src/change_log.cc
@@ -8,20 +8,14 @@
 #include "utility/logger.h"
 #include "tracking/change_tracker.h"
 
+// `true`  signals the interposed functions to execute tracking logic
+// `false` signals the interposed functions to do plain forwarding
+static bool enabled = false;
+
 static std::unique_ptr<utility::FileDescriptorGuard> fd_guard;
 static std::unique_ptr<utility::Logger>              logger;
 static std::unique_ptr<tracking::ChangeTracker>      tracker;
 
-void track_write(const int fd) {
-	if ( fd != *fd_guard && utility::is_regular_file(fd) ) {
-		const std::string file_name{ utility::get_file_name(fd) };
-
-		if ( !tracker->is_tracked(file_name) ) {
-			tracker->track(file_name);
-		}
-	}
-}
-
 void init() __attribute__ ((constructor));
 void init() {
 	if ( getenv("CHANGE_LOG_TARGET") != NULL ) {
@@ -40,6 +34,41 @@ void init() {
 	} else {
 		tracker = std::make_unique<tracking::ChangeTracker>(logger.get());
 	}
+
+	// tracking is only enabled when everything is initialized as both
+	// the actual tracking and the decision if a event should be tracked
+	// depend on `logger` and `tracker` being fully instantiated.
+	// In most cases this library will work correctly without delayed
+	// activation but e.g. `nvim` crashes as it performs tracked syscalls
+	// before `init` has been called.
+	enabled = true;
+}
+
+inline void track_write(const int fd) {
+	if ( enabled && fd != *fd_guard && utility::is_regular_file(fd) ) {
+		const std::string file_name{ utility::get_file_name(fd) };
+
+		if ( !tracker->is_tracked(file_name) ) {
+			tracker->track(file_name);
+		}
+	}
+}
+
+inline void track_rename(
+	const std::string& old_path, const std::string& new_path) {
+	if ( enabled ) {
+		if ( !tracker->is_tracked(old_path) ) {
+			tracker->track(old_path);
+		}
+
+		logger->append("renamed '", old_path, "' to '", new_path, "'");
+	}
+}
+
+inline void track_remove(const std::string& path) {
+	if ( enabled && utility::is_regular_file(path.c_str()) ) {
+		logger->append("removed '", path, "'");
+	}
 }
 
 ssize_t write(int fd, const void* buffer, size_t count) {
@@ -55,34 +84,28 @@ ssize_t writev(int fd, const iovec* iov, int iovcnt) {
 }
 
 int rename(const char* old_path, const char* new_path) {
-	if ( !tracker->is_tracked(old_path) ) {
-		tracker->track(old_path);
-	}
-
-	logger->append("renamed '", old_path, "' to '", new_path, "'");
+	track_rename(old_path, new_path);
 
 	return actual::rename(old_path, new_path);
 }
 
 int rmdir(const char* path) {
-	logger->append("removed directory '", path, "'");
+	track_remove(path);
 
 	return actual::rmdir(path);
 }
 
 int unlink(const char* path) {
-	if ( utility::is_regular_file(path) ) {
-		logger->append("remove '", path, "'");
-	}
+	track_remove(path);
 
 	return actual::unlink(path);
 }
 
 int unlinkat(int dirfd, const char* path, int flags) {
 	if ( dirfd == AT_FDCWD ) {
-		logger->append("removed '", path, "'");
+		track_remove(path);
 	} else {
-		logger->append("removed '", utility::get_file_name(dirfd), path, "'");
+		track_remove(utility::get_file_name(dirfd) + path);
 	}
 
 	return actual::unlinkat(dirfd, path, flags);
-- 
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