On Tue, Jun 17, 2025 at 10:07:07AM -0400, enh wrote: > On Mon, Jun 16, 2025 at 5:44 PM Alejandro Colomar <a...@kernel.org> wrote: > > > > Hi Florian, > > > > On Mon, Jun 16, 2025 at 09:35:01PM +0200, Florian Weimer wrote: > > > * Adhemerval Zanella Netto: > > > > > > > I have re-read the whole thread and it seems that most maintainers are > > > > OK > > > > with this change and agree that current POSIX's realloc spec has some > > > > drawbacks (albeit it still allows current glic behavior). > > > > > > > > The only one involved in the previous thread that raised some objection > > > > to > > > > this change was Joseph [1], but I will let to say if he still think this > > > > potential change to glibc is ill-advised. > > > > > > I objected then, and I'm objecting now as well. > > > > > > My rationale has not changed: > > > > > > <https://inbox.sourceware.org/libc-alpha/8734kl1pim....@oldenburg.str.redhat.com/> > > > > > > I believe Siddhesh's proposed patch as the time was mostly a device to > > > drive the discussion to a conclusion, which it did. > > > > I'll quote your rationale from the link: > > > > | * Siddhesh Poyarekar: > > | | Nope, please read the threads carefully; I actually said that I won't > > | | sustain an objection if I'm the only one holding that opinion. > > | > > | I'm still objecting, I don't think this change is valuable. > > | > > | I'm open to looking at this again once the C standard fully specifies > > | the behavior of zero-sized objects, the return value of malloc (0), and > > | so on. > > > > I'm working on that. I have a proposal for mandating that malloc(0), > > but I can't present it until realloc(p, 0) is fixed. And the > > C Committee has refused to fix realloc(p, 0) by decree, so until the > > remaining implementations that are broken fix their implementations, we > > can't think of having the standard fixed. > > > > Since glibc and Bionic are the two implementations that are currently > > broken, could you please fix your implementations? I'm sure the > > C Committee will be much easier to convince if the implentations have > > changed in a clear direction. > > > > But if the committee says we're not fixing ISO C until the > > implementations are fixed, and the implementations (you) refuse to > > accept the fix until the committee standardizes something, then we'll > > have the problem forever. > > is it really a problem though? you're basically asking to _add_ an > incompatibility with existing versions of glibc/bionic (so, you know, > "basically every non-Windows computer out there"). > > from my perspective: > > pros: > + code would then behave the same on android and ios > cons: > - code would behave differently on different versions of android > - code would behave differently on the host > unknowns: > ? what does Windows do? > ? does anyone actually care? > > not having heard anyone but you bring this up in the last 15 years > (despite it apparently being an android/ios difference), i'm inclined > to assume this is a non-problem that's not worth the disruption of > changing anything...
I'm not sure what you mean by "not having heard anyone but you bring this up in the last 15 years". This has been a recurring issue on the glibc bug tracker and in C and POSIX committees, and comes up all the time with users of the language not understanding what the standard says or if/how implementations are conforming. There have been multiple bug reports against different versions of the wording in different versions of the C and POSIX standards, and it's a perpetual source of disagreements. Indeed fixing the bug will not make any immediate improvement. For decades applications will still need to assume they might be running on a system with the broken (inconsistent) behavior like glibc or Bionic, or apply a wrapper to fix it (ala gnulib). But maybe eventually that can become a bad chapter of history we leave behind. One thing I kinda would like to think about is if there's a way we can signal at compile-time (without run tests that don't work for cross compiling) that realloc is non-broken and doesn't need gnulib-style wrapping/replacement. My hope is that such a mechanism would follow the principles of the "Macro-based advertisement of libc extensions" proposal on libc-coord. Rich
