Re: [musl] undefined behavior in fread.c

[enh <enh@google.com>]

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On Fri, Feb 24, 2023 at 8:40 AM Jₑₙₛ Gustedt <jens.gustedt@inria.fr> wrote:

>
> on Fri, 24 Feb 2023 11:12:11 -0500 you (Tamir Duberstein
> <tamird@google.com>) wrote:
>
> > I agree, the caller's behavior is UB. I'll send them (freetype2) a
> > patch.
> >
> > That said, do we want to avoid internal UB here anyway?
>
> I am not sure that I even understand what "internal UB" is supposed to
> mean.
>
> > - As mentioned earlier, glibc avoids the UB (and the lock).
> > - llvm-libc does the same starting with
> > https://github.com/llvm/llvm-project/commit/53c251b
> > - uclibc avoids the UB but still locks:
> > https://github.com/gittup/uClibc/blob/9dbf00b/libc/stdio/fread.c#L25
> > - FreeBSD avoids the UB but still locks:
> >
> https://svnweb.freebsd.org/base/head/lib/libc/stdio/fread.c?view=markup#l76
> > - Android (bionic) avoids the UB but still locks:
> >
> https://cs.android.com/android/platform/superproject/+/master:bionic/libc/stdio/stdio.cpp;l=1099;drc=4aa8f499f21ebf84101de34d68682d5388667001
> >
> > Does this persuade?
>
> Me personally not much. The only thing that would help applications to
> write portable code is to put an attribute on the pointer argument
> such that bad calls get diagnosed if possible.
>

(bionic's actually working on the larger "annotate all the functions"
project, but hasn't got as far as stdio.h yet :-) )


> Jₑₙₛ
>
> --
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