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Date: Thu, 21 May 2020 22:22:53 +0200
From: Harald Welte <laforge@...monks.org>
To: musl@...ts.openwall.com
Subject: MUSL ignores__attribute__((constructor(priority))) ?

Hi all!

While investigating some really strange behavior of osmocom software
on MUSL based systems (see https://osmocom.org/issues/4456)
there are two observations:

1) if there are multiple libraries (in this example libosmocore and libtalloc,
   where libosmocore depends on libtalloc), the __attribute__((constructor))
   functions are not called in inverse dependency order, i.e. the talloc
   ones are *not* called before those of libosmocore.

2) even when adding an explicit "priority" field like
   static __attribute__((constructor(65535))) void on_dso_load_ctx(void)
   the MUSL ld.so doesnt' seem to respect this, i.e. it still calls the
   constructor with the high priority value *before* the constructor of lower
   priority.  This is not as specified in https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Function-Attributes.html

I don't know whether '1' is a bug (i.e. whether it is valid to assume constructors
of libraries are executed in-line with library dependencies).   However, I am
quite convinced '2' is a bug.

Regards,
	Harald

p.s.: Please keep me in Cc, I'm not a subscriber to this list.

-- 
- Harald Welte <laforge@...monks.org>           http://laforge.gnumonks.org/
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