Launcher

A one file implementation of a simple launcher

Summary

The launcher will set some environment variables and launch your application, making it so that your libraries will spawn with these environment variables already set. These environment variables can also change at runtime, using the preInit() to setup the environment variables and postInit() to clean then up.

NOTE: THIS SHOULD NOT BE USED TO STORE SECRET ENVIRONMENT VARIABLES, IT IS EASY TO FIND THEM WITH A HEX EDITOR

Requirements

• clang or gcc with at least c++17 and c99

Compile command

• For MacOS/Linux
• For the C++ file c++ -o launcher launcher.cpp -std=c++17
• For the C file cc -o launcher launcher.c -std=c99

• For Windows
• For the C++ file c++ -o launcher.exe launcher.cpp -std=c++17
• For the C file cc -o launcher.exe launcher.cpp -std=c99

How to use

• Open up the lanuncher.h, inside there will be the following at the very top of the page. They will be the exact same inside the c file and the cpp file.

static const char* EXECUTABLE_PATH = "my_app";

static const char* ENVIRONMENT_VARIABLES[]
{
	"MY_VARIABLE", 			/* = */		"MY_VALUE",				/* Override? */		"true",
	"MY_OTHER_VARIABLE", 		/* = */		"MY_OTHER_VALUE",			/* Override? */		"false",
};

// #define LAUNCHER_NO_OPTIONS_CHECKING 1

void preInit(int argc, const char* argv[])
{
	//Change environment variables any way you want here, edit `ENVIRONMENT_VARIABLES` to `char**` if needed
}

void postInit(int argc, const char* argv[])
{
	//Free pointers if needed
}

• There are a few things to note LAUNCHER_NO_OPTIONS_CHECKING is a macro to disable debugging, by default it is off. It will print statuses, show errors and validate your inputs for the EXECUTABLE_PATH and ENVIRONMENT_VARIABLES variables.

EXECUTABLE_PATH is the path to your executable, it can use / or \ for folders and will automatically switch to the correct one depending on your platforms.

ENVIRONMENT_VARIABLES are the environment variables themselves. When you first open the file, you will see two default environment variables set

static const char* ENVIRONMENT_VARIABLES[]
{
	"MY_VARIABLE", 			/* = */		"MY_VALUE",				/* Override? */		"true",
	"MY_OTHER_VARIABLE", 		/* = */		"MY_OTHER_VALUE",			/* Override? */		"false",
};

The environment variables are in groups of three, looking at a single line, we can see this

"MY_VARIABLE", 				/* = */		"MY_VALUE",					/* Override? */		"true",

MY_VARIABLE is the name of the environment variable. MY_VALUE is the value of the environment variable. true is a either "true" or "false". If set to true, the environment variable will be set no matter what. If false, the environment variable will be set ONLY if the environment variable wasn't set before.

These lines can be as long as the computer allows.

We then have these two functions:

void preInit(int argc, const char* argv[])
{
	//Change environment variables any way you want here, edit `ENVIRONMENT_VARIABLES` to `char**` if needed
}

void postInit(int argc, const char* argv[])
{
	//Free pointers if needed
}

These have an argc and argv parameters, these can be used to edit the environment variables based on how the library was called. You can also use something like std::filesystem::current_path(). or an equivalent in C.

The preInit() function is called first thing inside the main() function. This can then be used to edit the executable path or the environment variables themselves if needed. You could also, but is highly unrecommended due to the easy reverse-engineering process, try having the environment variables encrypted and then decrypt them in the preInit() function for some rudimentary obfuscation.

The postInit() function is called right after the system() command to launch the application. You can use the function to free any memory you dynamically allocated in C or add a debug message.