r208146 - Try harder to ensure a strict weak ordering of overload candidates that

[Richard Smith]

Looking into this further, this function is supposed to establish a *total*
order, not just a strict weak order, for the overload candidates (see the
isBeforeInTranslationUnit tie-breaker at the end, and the caller who uses
std::sort not std::stable_sort).


On Tue, May 6, 2014 at 5:43 PM, Kaelyn Takata <rikka at google.com> wrote:

> Author: rikka
> Date: Tue May  6 19:43:38 2014
> New Revision: 208146
>
> URL: http://llvm.org/viewvc/llvm-project?rev=208146&view=rev
> Log:
> Try harder to ensure a strict weak ordering of overload candidates that
> have arity mismatches.
>
> Modified:
>     cfe/trunk/include/clang/Sema/Overload.h
>     cfe/trunk/lib/Sema/SemaOverload.cpp
>
> Modified: cfe/trunk/include/clang/Sema/Overload.h
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Overload.h?rev=208146&r1=208145&r2=208146&view=diff
>
> ==============================================================================
> --- cfe/trunk/include/clang/Sema/Overload.h (original)
> +++ cfe/trunk/include/clang/Sema/Overload.h Tue May  6 19:43:38 2014
> @@ -679,6 +679,18 @@ namespace clang {
>
>        return CanFix;
>      }
> +
> +    unsigned getNumParams() const {
> +      if (IsSurrogate) {
> +        auto STy = Surrogate->getConversionType();
> +        while (STy->isPointerType() || STy->isReferenceType())
> +          STy = STy->getPointeeType();
> +        return STy->getAs<FunctionProtoType>()->getNumParams();
> +      }
> +      if (Function)
> +        return Function->getNumParams();
> +      return ExplicitCallArguments;
> +    }
>    };
>
>    /// OverloadCandidateSet - A set of overload candidates, used in C++
>
> Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=208146&r1=208145&r2=208146&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaOverload.cpp Tue May  6 19:43:38 2014
> @@ -9260,12 +9260,17 @@ struct CompareOverloadCandidatesForDispl
>            L->FailureKind == ovl_fail_too_few_arguments) {
>          if (R->FailureKind == ovl_fail_too_many_arguments ||
>              R->FailureKind == ovl_fail_too_few_arguments) {
> -          if (!L->Function || !R->Function) return !R->Function;
> -          int LDist = std::abs((int)L->Function->getNumParams() -
> (int)NumArgs);
> -          int RDist = std::abs((int)R->Function->getNumParams() -
> (int)NumArgs);
> -          if (LDist == RDist)
> -            return L->FailureKind == ovl_fail_too_many_arguments &&
> -                   R->FailureKind == ovl_fail_too_few_arguments;
> +          int LDist = std::abs((int)L->getNumParams() - (int)NumArgs);
> +          int RDist = std::abs((int)R->getNumParams() - (int)NumArgs);
> +          if (LDist == RDist) {
> +            if (L->FailureKind == R->FailureKind)
> +              // Sort non-surrogates before surrogates.
> +              return !L->IsSurrogate && R->IsSurrogate;
> +            // Sort candidates requiring fewer parameters than there were
> +            // arguments given after candidates requiring more parameters
> +            // than there were arguments given.
> +            return L->FailureKind == ovl_fail_too_many_arguments;
> +          }
>            return LDist < RDist;
>          }
>          return false;
>
>
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