C Run-Time Library reimplementer for the MSVC compiler.
Note
This project is not intended as a full replacement for the CRT, but it can significantly simplify the integration of projects that rely on the CRT. Many functions may still be missing, but the author has successfully linked Lua 5.4.7 in their own Non-CRT project.
CRT-0 is a small extension for VC++ projects where the CRT needs to be disabled. This may be necessary for projects that require greater control over the internal functions of the C library.
When using the /NODEFAULTLIB flag in MSVC, the linker does not include the library that provides implementations of various functions - from basic ones like tolower or strcpy to more complex ones like sprintf or acos. The project also loses the CRT-specific entry point _DllMainCRTStartup/mainCRTStartup. This provides a high degree of control over the runtime environment, but at the same time requires giving up all the functions that are normally linked by default.
This usually doesn't cause issues if the developer already has their own set of functions capable of replacing the CRT core. However, there are cases when it's necessary to integrate third-party projects that actively use C functions - for example, Lua. Adapting such projects can be too burdensome, so it's often much easier to simply reimplement the functions they rely on, allowing the linker to resolve them from your own files.
This is exactly what CRT-0 does - it provides the linker with the same functions that would normally be linked if the /NODEFAULTLIB flag were not used.
Some developers simply define macros that redirect to their own implementations. For example:
#define strcpy(d, s) my_strcpy(d, s)This can be convenient and even more correct in some cases. However, when working with MSVC, it can lead to conflicts with CRT header files and other macro-related issues. Ultimately, you'll still need to modify the source code of the projects that use CRT functions. The reimplementation approach helps minimize such modifications - although in rare cases, some editing may sti 6182 ll be necessary, it is required to a much lesser extent.
Simply add all .cpp files to your project so the compiler can build the functions that will serve as CRT alternatives. Use the standard development environment headers (cstring, etc.).
CRT-0 assumes that you will not use Thread Local Storage in your project (e.g., static variables inside functions, thread_local, etc.), as this is considered overhead. Use the /Zc:threadSafeInit- flag to prevent the generation of TLS-related code for static variables within functions.
In general, any options related to the CRT should be disabled. This includes Basic Runtime Checks, C++ Exceptions, Runtime Library, Security Check, SDL checks, and Run-Time Type Information. If any of these options are enabled, CRT-0 is likely to fail to compile due to linkage conflicts.
The project has only been built and tested for Windows, x64. Other configurations have not been thoroughly tested, and it is unlikely that CRT-0 will work for them. CRT-0 definitely cannot be built for x32 due to the compiler implicitly inserting functions like __alldiv, __allrem, etc., when handling 64-bit arithmetic.
This product is distributed under the MIT-0 License.