Re: [Libguestfs] [PATCH nbdkit 0/2] common: Add checked-overflow macros
On Tue, Nov 09, 2021 at 05:49:16PM +0000, Richard W.M. Jones wrote:
In common/vector/vector.c use GCC/Clang built-in overflow operators.
The first patch is a neutral change which adds comments. The second
patch is the actual change.
Add a new header "checked-overflow.h" which has the purpose of
isolating the use of the built-ins to one file (in case we need to add
a new compiler later). Then use this in generic_vector_reserve.
I tested this with GCC 11 and Clang 13.
That's the modern edge of the spectrum; will we be interfering with
compilation on older distros with older compilers? I guess CI testing
can help find that out quickly.
I verified by disassembly that "jo" (jump overflow) / "jno" is used
where it was not used previously, by both compilers.
Nice, and an argument in favor of doing this.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org