Inconsistent line numbers between __LINE__ and clang SourceLocation

[glugalug]

For multi-line macros, the SourceLocation of symbols generated by the macro expansion in the clang AST is the first line of the macro. But __LINE__ is expanding to the line number of the last line of it.

Should these be the same?

[AaronBallman]

Can you post a code example so we can be sure we're thinking of the same code? __LINE__ should expand to the value of the expansion line. e.g., https://godbolt.org/z/ebdM3jW9o

This is because the line splices are deleted in an earlier phase of translation (so the macro expansion list is all on the same logical source line), but __LINE__ isn't resolved until after it is macro replaced. So in my example, MLM is first expanded to the additions with __LINE__, then the resulting tokens are rescanned for further macro replacement, which replaces __LINE__ with the line number of the expansion.

As for SourceLocation, in Clang the SourceLocation generally points to the start of the token which generated it.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (glugalug)

For multi-line macros, the SourceLocation of symbols generated by the macro expansion in the clang AST is the first line of the macro. But `__LINE__` is expanding to the line number of the last line of it.

Should these be the same?