[zturner]

1) ABI compatibility is not present. With clang-cl you can compile half of your object files with MSVC and half with clang-cl, and link them together. That's very powerful. You might be thinking "but who is really gonna do that anyway?" However, there is more to the ABI than just this. For example, consider what happens if you need to use Structured Exception Handling. Well, with GCC, you can't.

2) Debug Information. GCC does not emit PDBs, it emits DWARF. This means you cannot use Visual Studio to debug, you cannot use vTune or WPA to profile, you cannot use symbol / source servers.

3) There are licensing implications, GPL != BSD and it's easier to use BSD.

These are the main reasons. There are other reasons though, such as if the entire goal is to get down to 1 toolchain and that toolchain is X, then why would you waste your time converting Y to Z?

[tavert]

> if you need to use Structured Exception Handling. Well, with GCC, you can't

You can on 64 bit.