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Date: Tue, 10 Mar 2020 10:59:49 +0100
From: Szabolcs Nagy <>
Cc: Kaisrlí, Jan <>
Subject: Re: musl and jemalloc support

* Kaisrlík, Jan <> [2020-03-10 10:32:08 +0100]:
> I would like to ask about the support of external malloc and jemalloc.
> I find an old mail in ML claiming that support is not there and using
> external malloc function can potentially cause problems[1] and a
> thread[2] on jemalloc saying the same. On the other hand, I find a lot
> of pages comparing speed like pages [3] and also I noticed that Musl
> claims "replacement of malloc is now allowed/supported" statement in
> changelog [4]. So, my expectation is Musl from version 1.1.20 supports
> the loading of external malloc function and it is working. Is my
> assumption correct? Does it have any limitations, e.g., it has to be
> done in compilation time, is LD_PRELOAD supported?

yes, it just works.

> The reason why I'm asking is that some apps started crashing with a
> weird coredump from the moment I used
> LD_PRELOAD=/usr/lib/

the preloaded libraries obviously have to be built against musl.
(in some cases a glibc linked library would work, i would expect
a glibc linked malloc library to work with musl on x86_64, but
there is no guarantee)

the fact that you have means it's not a musl system
and preloading a from another libc is expected to
crash. (even on other systems you should not just preload libpthread,
but libjemalloc should have it in its dependencies if needed.)

> Thank you for your answer.
> The best,
> Jan
> [1]:
> [2]:
> [3]:
> [4]:

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