[llvm-dev] [SemaCXX] Should we fix test failing due to reverse iteration?

[Grang, Mandeep Singh via llvm-dev]

I see that the following test fails if reverse iteration of SmallPtrSet 
is enabled:

/clang/test/SemaCXX/warn-loop-analysis.cpp/

This is because in SemaStmt.cpp we iterate SmallPtrSet and output 
warnings about the variables not used in the loop.

Expected output: /warning: variables 'i', 'j', and 'k' used in loop 
condition not modified/

Output with reverse iteration: /warning: variables 'k', 'j', and 'i' 
used in loop condition not/

I would like the community's opinion on whether this is something worth 
fixing? In this case, should the output always be the same irrespective 
of the iteration order?

If yes, then we have 2 alternatives:

1. Change SmallPtrSet to SmallVector for the container (VarDecls) being 
iterated - this may have a compile time impact (need to measure).

2. Sort the container (VarDecls) before iteration. We can sort based on 
decl source location and decl name. Not sure if these guaranteed to be 
unique?

Thanks,

Mandeep

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