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Date: Wed, 29 Jun 2022 18:30:19 +0200
From: Thomas Stüfe <>
To: Florian Weimer <>
Subject: Re: Question about calloc, free in CPU_ALLOC and CPU_FREE

On Wed, Jun 29, 2022 at 6:15 PM Florian Weimer <> wrote:

> * Thomas Stüfe:
> > Greetings,
> >
> > I have a small question about the way muslc implements the CPU_ALLOC and
> > 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()

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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