[all-commits] [llvm/llvm-project] c53117: Fix invalid overflow check in flang

[serge-sans-paille via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c531171d995728f55e5775d354a21dceed03edce
      https://github.com/llvm/llvm-project/commit/c531171d995728f55e5775d354a21dceed03edce
  Author: serge-sans-paille <sguelton at redhat.com>
  Date:   2022-03-30 (Wed, 30 Mar 2022)

  Changed paths:
    M flang/runtime/command.cpp

  Log Message:
  -----------
  Fix invalid overflow check in flang

Statically checking for overflow with

    if constexpr (sizeof(std::size_t) <= sizeof(std::int64_t)) {
         return static_cast<std::int64_t>(length);
    }

Doesn't work if `sizeof(std::size_t) == sizeof(std::int64_t)` because std::size_t
is unsigned.

if `length == std::numeric_limits<size_t>` casting it to `int64_t` is going to overflow.

This code would be much simpler if returning a `uint64_t` instead of a signed
value...

Differential Revision: https://reviews.llvm.org/D122705