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Message-ID: <CAA-vtUxxgZfUXrBrSvFyRzVaikxog=014mwo=gHpFyfgLjVZZQ@mail.gmail.com>
Date: Wed, 29 Jun 2022 18:30:19 +0200
From: Thomas Stüfe <thomas.stuefe@...il.com>
To: Florian Weimer <fweimer@...hat.com>
Cc: musl@...ts.openwall.com
Subject: Re: Question about calloc, free in CPU_ALLOC and CPU_FREE
On Wed, Jun 29, 2022 at 6:15 PM Florian Weimer <fweimer@...hat.com> wrote:
> * Thomas Stüfe:
>
> > Greetings,
> >
> > I have a small question about the way muslc implements the CPU_ALLOC and
> CPU_FREE
> > macros.
> >
> > I see them defined in sched.h as:
> >
> > #define CPU_ALLOC(n) ((cpu_set_t *)calloc(1,CPU_ALLOC_SIZE(n)))
> > #define CPU_FREE(set) free(set)
> >
> > whereas the glibc defines them as calls to functions __sched_cpu_alloc()
> and
> > __sched_cpufree():
> >
> > #define __CPU_ALLOC(count) __sched_cpualloc (count)
> > #define __CPU_FREE(cpuset) __sched_cpufree (cpuset)
> >
> > in the end both variants allocate from C-heap, but the muslc variant
> > gets inlined directly into the calling code. If that calling code has
> > a function "free" or "calloc" (okay, less likely) these get called
> > instead. Could also be a class local method in C++.
>
> calloc and free can be macros, and if an implementation exercises this
> possibility, you will have some trouble defining your own functions of
> the same name. We ran into this issue when we added an iszero macro to
> glibc as part of support for future C revisions. In the end, we had to
> use an alternative C++ construct in C++ mode instead of the preprocessor
> macro we use for C: too many C++ applications broke because they used
> iszero as a member function name.
>
> I think I can guess which code base this is about. 8-) You really should
> adopt a non-colliding naming scheme for your os:: wrapper functions.
> This sidesteps this entire set of issues.
>
>
:-) I guess you guess right.
Yes, the JVM crashes on Alpine because of ::malloc() -> os::free()
disbalance: https://bugs.openjdk.org/browse/JDK-8289477
And you are absolutely right. We should change the naming scheme.
> There really isn't a musl bug here, I think (but I'm not a musl
> developer).
>
>
I think so too now.
> Thanks,
> Florian
>
>
Thank you, Thomas
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