[PATCH] D27163: Introduce -f[no-]strict-return flag that controls code generation for C++'s undefined behaviour return optimisation

[Richard Smith via Phabricator via cfe-commits]

rsmith added a comment.

In https://reviews.llvm.org/D27163#607078, @rsmith wrote:

> A target-specific default for this, simply because there's a lot of code on Darwin that happens to violate this language rule, doesn't make sense to me.


... but rjmccall's explanation of the problem helps. The C compatibility argument also suggests that this should only apply to trivially-copyable types, and perhaps only scalar types. The same issue presumably arises for `-fstrict-enums`, which is again only UB in C++? (Also, C has rather different and much less useful TBAA rules.) Perhaps some catch-all "I want defined behavior for things that C defines even though I'm compiling in C++" flag would make sense here?


Repository:
  rL LLVM

https://reviews.llvm.org/D27163