Can I compile C or C++ code to platform-independent LLVM bitcode?
No. C and C++ are inherently platform-dependent languages. The most obvious example of this is the preprocessor. A very common way that C code is made portable is by using the preprocessor to include platform-specific code. In practice, information about other platforms is lost after preprocessing, so the result is inherently dependent on the platform that the preprocessing was targeting. Another example is sizeof. It’s common for sizeof(long) to vary between platforms. In most C front-ends, sizeof is expanded to a constant immediately, thus hard-wiring a platform-specific detail. Also, since many platforms define their ABIs in terms of C, and since LLVM is lower-level than C, front-ends currently must emit platform-specific IR in order to have the result conform to the platform ABI.
