Update the overflow functions to include qsizetype

Commit 29bc68cf169b8cf87d306a1c72e12eb9b6fbfce7 added support for
unsigned and commit 5ff7a3d96e0ce0dcb3d388b53d038cdd40c7a975 later added
support for int. This commit adds support for qsizetype, which isn't int
on 64-bit platforms.

We do this by reorganizing the code and using the generic version of
__builtin_{add,sub,mul}_overflow from GCC 5 and Clang 3.8, which ICC 18
seems to support now too on Linux. That leaves older versions of GCC and
Clang, as well as MSVC, ICC on Windows, and the GHS compiler, to use the
generic implementations, as I've removed the assembly code those
versions of GCC and Clang on x86 are now uncommon.

Note: any older version of ICC probably breaks. We only support the
latest.

Change-Id: I9e2892cb6c374e93bcb7fffd14fc11bcd5f067a7
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

0 files changed, 0 insertions, 0 deletions