From 61c717e6d668476717f74fb68e4b690a86917cd4 Mon Sep 17 00:00:00 2001
From: Robert Knight <robertknight@gmail.com>
Date: Fri, 16 Sep 2011 14:35:49 +0100
Subject: [PATCH] Temporarily change the current directory to that of the main
 binary when re-launching the application.

This may be required on Windows so that the application can find libraries
that it depends upon.
---
 src/FileUtils.cpp       | 35 +++++++++++++++++++++++++++++
 src/FileUtils.h         |  6 +++++
 src/UpdateInstaller.cpp | 49 +++++++++++++++++++++++++++--------------
 3 files changed, 74 insertions(+), 16 deletions(-)

diff --git a/src/FileUtils.cpp b/src/FileUtils.cpp
index d817b65..e1e7efe 100644
--- a/src/FileUtils.cpp
+++ b/src/FileUtils.cpp
@@ -516,3 +516,38 @@ std::string FileUtils::makeAbsolute(const char* path, const char* basePath)
 		return path;
 	}
 }
+
+void FileUtils::chdir(const char* path) throw (IOException)
+{
+#ifdef PLATFORM_UNIX
+	if (::chdir(path) != 0)
+	{
+		throw FileUtils::IOException("Unable to change directory");
+	}
+#else
+	if (!SetCurrentDirectory(path))
+	{
+		throw FileUtils::IOException("Unable to change directory");
+	}
+#endif
+}
+
+std::string FileUtils::getcwd() throw (IOException)
+{
+#ifdef PLATFORM_UNIX
+	char path[PATH_MAX];
+	if (!::getcwd(path,PATH_MAX))
+	{
+		throw FileUtils::IOException("Failed to get current directory");
+	}
+	return std::string(path);
+#else
+	char path[MAX_PATH];
+	if (GetCurrentDirectory(MAX_PATH,path) != 0)
+	{
+		throw FileUtils::IOException("Failed to get current directory");
+	}
+	return toUnixPathSeparators(std::string(path));
+#endif
+}
+
diff --git a/src/FileUtils.h b/src/FileUtils.h
index 12856ca..ff7afdb 100644
--- a/src/FileUtils.h
+++ b/src/FileUtils.h
@@ -119,5 +119,11 @@ class FileUtils
 		static std::string makeAbsolute(const char* path, const char* basePath);
 
 		static void writeFile(const char* path, const char* data, int length) throw (IOException);
+
+		/** Changes the current working directory to @p path */
+		static void chdir(const char* path) throw (IOException);
+
+		/** Returns the current working directory of the application. */
+		static std::string getcwd() throw (IOException);
 };
 
diff --git a/src/UpdateInstaller.cpp b/src/UpdateInstaller.cpp
index 866f868..77fa4bc 100644
--- a/src/UpdateInstaller.cpp
+++ b/src/UpdateInstaller.cpp
@@ -402,27 +402,44 @@ void UpdateInstaller::setObserver(UpdateObserver* observer)
 
 void UpdateInstaller::restartMainApp()
 {
-	std::string command;
-	std::list<std::string> args;
-
-	for (std::vector<UpdateScriptFile>::const_iterator iter = m_script->filesToInstall().begin();
-	     iter != m_script->filesToInstall().end();
-	     iter++)
+	try
 	{
-		if (iter->isMainBinary)
+		std::string command;
+		std::list<std::string> args;
+
+		for (std::vector<UpdateScriptFile>::const_iterator iter = m_script->filesToInstall().begin();
+			iter != m_script->filesToInstall().end();
+			iter++)
 		{
-			command = m_installDir + '/' + iter->path;
+			if (iter->isMainBinary)
+			{
+				command = m_installDir + '/' + iter->path;
+			}
+		}
+
+		if (!command.empty())
+		{
+			LOG(Info,"Starting main application " + command);
+
+			// change the current directory to that of the application binary,
+			// so that on Windows the application can find shared libraries
+			// that it depends on which are in the same directory
+			std::string appDir = FileUtils::dirname(command.c_str());
+			std::string currentDir = FileUtils::getcwd();
+			FileUtils::chdir(appDir.c_str());
+
+			ProcessUtils::runAsync(command,args);
+
+			FileUtils::chdir(currentDir.c_str());
+		}
+		else
+		{
+			LOG(Error,"No main binary specified in update script");
 		}
 	}
-
-	if (!command.empty())
+	catch (const std::exception& ex)
 	{
-		LOG(Info,"Starting main application " + command);
-		ProcessUtils::runAsync(command,args);
-	}
-	else
-	{
-		LOG(Error,"No main binary specified in update script");
+		LOG(Error,"Unable to restart main app " + std::string(ex.what()));
 	}
 }