On 16 July 2014 10:28, Florian Weimer <fweimer@xxxxxxxxxx> wrote: > On 07/16/2014 11:00 AM, Jakub Jelinek wrote: >> >> On Wed, Jul 16, 2014 at 10:55:57AM +0200, Florian Weimer wrote: >>> >>> On 07/15/2014 07:22 PM, Adam Jackson wrote: >>>> >>>> On Tue, 2014-07-15 at 10:40 -0600, Orion Poplawski wrote: >>>>> >>>>> Did you know that "char" defaults to "signed char" on x86 but "unsigned >>>>> char" >>>>> on ppc and arm? I didn't. >>>> >>>> >>>> Yep, found that out the hard way. It annoyed me enough that I went >>>> digging in the gcc source to find the answer for all platforms: >>>> >>>> http://ajax.fedorapeople.org/is-char-signed-or-not.txt >>> >>> >>> Any idea why aarch64 and ppc64le got this wrong? >> >> >> Why is char == unsigned char wrong? Because i?86/x86_64 do it >> differently? > > > Yes, it looks like a totally avoidable portability hazard. iOS has signed > chars as well, so even when considering current ARM, the natural choice is > unclear. Older ARMs couldn't perform sign-extending 8-bit loads in a single > instruction, but that's true for historic x86, too, and yet even the old > 16-bit compilers used signed chars. > > History aside, I assumed that the idea behind both architectures (aarch64 > and ppc64le) is to use it to run current general-purpose server loads, and > those are predominantly x86 right now. That's why picking unsigned chars > puzzles me. > Implementation defined in all iterations of the C standard. End of story really. -- imalone http://ibmalone.blogspot.co.uk -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
