[PATCH] D101192: Add support for #elifdef and #elifndef

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added a comment.

> In this version of the patch, I am supporting the feature in all C and C++ modes. This seems like more useful functionality than diagnosing an unknown preprocessor directive in older language modes, and is a conforming extension in those modes anyway as use of an unknown directive is undefined behavior.

Is this really true? I think:

  #define X
  #if 0
  #elifdef X
  #error
  #endif

... is a valid translation unit in C++ and is strictly conforming in C11 and earlier; any //conditionally-supported-directive// (using the C++ terminology) within a //group// is ignored when skipping that //group//.

That said... applying this to all language modes does seem like the right choice, even though it may be technically non-conforming.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D101192/new/

https://reviews.llvm.org/D101192