aaron.ballman added a comment.

In D58154#1418594 <https://reviews.llvm.org/D58154#1418594>, @jyknight wrote:

> The errors disabled by this feature are default-error warnings -- you can 
> already get the same effect by using -Wno-<lots-of-things>. Why is it bad to 
> additionally allow -fpermissive to disable them? (If we have any diagnostics 
> which are currently default-on-warnings which should not _ever_ be 
> disable-able, then maybe we should just fix those?)


I believe -fpermissive controls more than just default-error warnings in GCC, 
and that's the kind of stuff I really don't want to support. For instance, 
there's no warning flag for this nonsense, but GCC accepts it under 
-fpermissive: https://godbolt.org/z/Q-Fl0i (If you think "but who does that?", 
this blog post shows up on the first page of a popular search engine when I 
search for fpermissive: 
http://blog.binchen.org/posts/always-turn-on-fpermissive-for-gcc-4-6.html). 
Another example of -fpermissive that I've seen in the wild is: 
https://godbolt.org/z/-44pK5 (which is warned on in C, but not controllable via 
a warning flag in C++). If we're going to claim support for -fpermissive as a 
GCC compatibility feature, then we'll get requests to support dialects like the 
above examples at some point as well and that's where my concern comes in -- I 
don't think we should ever support that kind of broken code.

I'd be fine with what's proposed here under a different flag name though.


Repository:
  rC Clang

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D58154/new/

https://reviews.llvm.org/D58154



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