[clang] [llvm] Enable fexec-charset option (PR #138895)

[Abhina Sree via llvm-commits]

abhina-sree wrote:

Hi, 
I'd like to discuss and clarify how we should handle the interaction of wide characters and fexec-charset. The standard states

> A character literal that begins with the letter L, such as L'x', is a wide-character literal. A wide-character literal has type wchar_t. The value of a wide-character literal containing a single c-char has value equal to the numerical value of the encoding of the c-char in the execution wide-character set. (2.13.2 Character literals)

which seems to imply 'L'a' == 'a' . If the fexec-charset and fwide-exec-charset are not compatible, this condition will fail. Should we allow fexec-charset to translate single wide characters to meet this condition if the fwide-exec-charset is not explicity specified?

https://github.com/llvm/llvm-project/pull/138895