[clang] 857bf5d - [FIX] Do not copy an llvm::function_ref if it has to be reused

[Johannes Doerfert via cfe-commits]

Some buildbots, I think only Windows buildbots for some reason, crashed 
in this function.

The reason, as described, is that an `llvm::function_ref` cannot be 
copied and then reused. It just happened to work on almost all 
configurations.

The change was not a "shot in the dark" but identified as proper fix by 
examining the `llvm::function_ref` implementation.

I could not reproduce the error on any machine I had immediately access 
to so maybe you can call that part "shot in the dark".


I'm not sure what else you want me to add here as a explanation but 
please let me know if there is anything I can do.


On 3/22/20 12:21 AM, David Blaikie wrote:
> "a problem" seems a smidge vague - was there a specific explanation for the
> kind of problem that was signalled? Or was this fix a bit of a shot in the
> dark?
>
> On Sat, Feb 15, 2020 at 10:55 PM Johannes Doerfert via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
>> Author: Johannes Doerfert
>> Date: 2020-02-16T00:51:11-06:00
>> New Revision: 857bf5da35af8e1f9425e1865dab5f5fce5e38f2
>>
>> URL:
>> https://github.com/llvm/llvm-project/commit/857bf5da35af8e1f9425e1865dab5f5fce5e38f2
>> DIFF:
>> https://github.com/llvm/llvm-project/commit/857bf5da35af8e1f9425e1865dab5f5fce5e38f2.diff
>>
>> LOG: [FIX] Do not copy an llvm::function_ref if it has to be reused
>>
>> Some buildbots signaled a problem in this method when the
>> llvm::function_ref was copied and reused after 1228d42ddab8. To
>> eliminate the problem we avoid copying the llvm::function_ref and
>> instead we pass it as a const reference.
>>
>> Added:
>>
>>
>> Modified:
>>      clang/include/clang/AST/OpenMPClause.h
>>
>> Removed:
>>
>>
>>
>>
>> ################################################################################
>> diff  --git a/clang/include/clang/AST/OpenMPClause.h
>> b/clang/include/clang/AST/OpenMPClause.h
>> index a3831fd5950f..453c068bbeb0 100644
>> --- a/clang/include/clang/AST/OpenMPClause.h
>> +++ b/clang/include/clang/AST/OpenMPClause.h
>> @@ -6682,10 +6682,10 @@ struct OMPTraitInfo {
>>     llvm::SmallVector<OMPTraitSet, 4> Sets;
>>
>>     bool anyScoreOrCondition(
>> -      llvm::function_ref<bool(Expr *&, bool /* IsScore */)> Cond) {
>> -    return llvm::any_of(Sets, [Cond](OMPTraitInfo::OMPTraitSet &Set) {
>> +      const llvm::function_ref<bool(Expr *&, bool /* IsScore */)> &Cond) {
>> +    return llvm::any_of(Sets, [&Cond](OMPTraitInfo::OMPTraitSet &Set) {
>>         return llvm::any_of(
>> -          Set.Selectors, [Cond](OMPTraitInfo::OMPTraitSelector &Selector)
>> {
>> +          Set.Selectors, [&Cond](OMPTraitInfo::OMPTraitSelector
>> &Selector) {
>>               return Cond(Selector.ScoreOrCondition,
>>                           /* IsScore */ Selector.Kind !=
>>                               llvm::omp::TraitSelector::user_condition);
>>
>>
>>
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