Getting rid of the C runtime library on Windows

NO RUNTIME!!!

Nov 23, 2024

Something that has been on my mind for a while is getting rid of the C runtime library (CRT) in order to reduce the size of Windows executables and make them more portable.

While googling around, I found a video by Dani Crunch going into detail about how to do this.

Here is a written version of the steps he took:

Configuration

First, we need to configure the project to not use the CRT. This can be done by setting the following flags in the project settings:

C/C++ -> Code Generation -> Security Check: Disable Security Check (/GS-)
Linker -> General -> Enable Incremental Linking: No (/INCREMENTAL:NO)
Linker -> Input -> Ignore All Default Libraries: Yes (/NODEFAULTLIB)
Linker -> System -> SubSystem: Console (/SUBSYSTEM:CONSOLE)
Linker -> System -> Entry Point: mainCRTStartup or your custom entry Point
Add /Gs9999999 to the Additional Options field to effectively disable stack probes for functions with large stack allocations. (-mno-stack-arg-probe)

Don't forget to add any additional libraries you need to the Linker -> Input -> Additional Dependencies field.

CMake

Edited on 2025-02-02 to add CMake instructions.

If you are using CMake, you can add the following code to your CMakeLists.txt file to set the necessary flags:

if(MSVC)
    add_compile_options(/GS- /Zl /GR- /EHa-)
    add_link_options(/NODEFAULTLIB /ENTRY:main /SUBSYSTEM:CONSOLE kernel32.lib ws2_32.lib user32.lib)
    set(CMAKE_C_FLAGS_DEBUG "/D_DEBUG")
    set(CMAKE_C_FLAGS_RELEASE "/DNDEBUG")
elseif(CMAKE_C_COMPILER_ID STREQUAL "GNU")
    set(CMAKE_C_FLAGS_DEBUG "-D_DEBUG")
    set(CMAKE_C_FLAGS_RELEASE "-DNDEBUG")
endif()

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