commit 567cedcc5f99aae2db9c7f124b7f3a6f4b5ec57d
author Behdad Esfahbod <behdad@behdad.org> Mon Feb 22 22:09:15 2021 -0700
committer Behdad Esfahbod <behdad@behdad.org> Mon Feb 22 22:32:42 2021 -0700
tree eb87aff694f64e4047f74c11fa6864edb775dcae
parent f4f35a4d5fd595bc6887b9951f1c92ce4d100fe8

Narrow down cast operators on IntType

Say for USHORT, we were implementing casts from and to unsigned.
With this change, we cast from and to uint16_t only.  This allows
compiler more opportunities to catch possible narrowing issues in
the code.

It needed a couple of fixes in the codebase though, because
previously, if a USHORT was participating in arithmetic with signed
numbers, eg. "u + 1", the result would have been unsigned.  With
this change, it would be signed.  The correct fix is to update the
code to read "u + 1u".

That said, I think about conditionally adding back the cast
out to signed/unsigned, to facilitate better type deduction.
But I couldn't think of a real situation where that would help
with anything.  So I didn't add.  Here's what it was:

  template <typename Type2 = hb_conditional<hb_is_signed (Type), signed, unsigned>,
           hb_enable_if (sizeof (Type) < sizeof (Type2))>
  operator hb_type_identity_t<Type2> () const { return v; }

https://github.com/harfbuzz/harfbuzz/pull/2875