1 - ArgIdx in Sema::AddOverloadCandidate looks like it overflows

[shafik]

Static analysis flagged the 1 - ArgIdx as possibly leading to overflow:

llvm-project/clang/lib/Sema/SemaOverload.cpp

Line 7196 in f75dce4

PO == OverloadCandidateParamOrder::Reversed ? 1 - ArgIdx : ArgIdx;

Looking at somewhat related code maybe it was meant to be Args.size() - 1 - ArgIdx.

[shafik]

CC @zygoloid since this was introduced via 974c8b7

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Shafik Yaghmour (shafik)

Static analysis flagged the `1 - ArgIdx` as possibly leading to overflow:

llvm-project/clang/lib/Sema/SemaOverload.cpp

Line 7196 in f75dce4

PO == OverloadCandidateParamOrder::Reversed ? 1 - ArgIdx : ArgIdx;

Looking at somewhat related code maybe it was meant to be Args.size() - 1 - ArgIdx.

[zygoloid]

OverloadCandidateParamOrder::Reversed is only used for overloaded comparison operators, for which the number of arguments is always 2 here. Maybe we could add something like

assert(PO != OverloadCandidateParamOrder::Reversed || Args.size() == 2);