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List:       busybox
Subject:    Re: Question: Finding libraries that are required for busybox??
From:       Eli Schwartz <eschwartz () archlinux ! org>
Date:       2018-06-26 21:38:16
Message-ID: 4e6a0f33-389e-8ffc-a32b-d228501221cb () archlinux ! org
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On 06/26/2018 07:37 AM, Walter Harms wrote:
> there is no static version of gnu-libc.

There is absolutely a libc.a provided by GNU libc, and you can
statically link it on account of it's a static library.

I'm looking at it right now, along with the binaries which are,
successfully, statically linked to it.

> But i agree there is other to really know what is needed.
> Dynamic libraries by there very name are dynamic and may link
> other libraies in without notice, i doubt ldd will be clever enought
> to see this.

This has absolutely nothing to do with dynamic vs. static libs.

Static libraries are part of the binary, and dynamic libraries are *very
clearly* marked as required, as ldd, readelf, objdump, or literally
anything else which checks ELF headers can attest.

dlopen() is a *third* way of "linking" a library, and any or all three
methods can be used in the same ELF file.

> In the give case ldd may be ok, but it is clearly not fool-proof and
> a runtime test is always required.

ldd is never okay, because it cannot detect dlopen().

Nothing can, except for running the binary and tracing the calls it makes.

-- 
Eli Schwartz
Bug Wrangler and Trusted User


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