Date: Thu, 28 May 2020 15:29:22 -0400 From: Rich Felker <dalias@...c.org> To: Jeffrey Walton <noloader@...il.com> Cc: musl@...ts.openwall.com Subject: Re: Shared library loading On Thu, May 28, 2020 at 03:20:46PM -0400, Jeffrey Walton wrote: > On Wed, May 27, 2020 at 2:10 PM Dmitry Samersoff <dms@...ersoff.net> wrote: > > > > > The "b" library loading works on my Ubuntu 19.10 and > > > fails on Alpine 3.11.6 with message: > dlopen failed: Error loading shared library liba.so: No such file or > > > directory (needed by /root/load-lib-sample/bin/b/libb.so) > > > Should it work on Alpine with musl libc as well? > > > > 1. You explicitly load library with a path (.../liba.so) > > > > 2. You are explicitly loading another library (.../libb.so) > > > > 3. Linker find liba.so in the appropriate section of libb.so and > > attempts to load it from syspath (LD_LIBRARY_PATH etc) > > > > 4. Linker doesn't find it. Musl return error on this step but glibc and > > BSD go further. > > > > 5. Linker compares short names of already loaded library and the > > required one > > > > 6. It matches, so Linker decides to resolve > > > > I didn't find any specification that dictates one or other behavior, so > > it could not be considered as a bug. > > I believe Drepper's DSO HowTo specifies the behavior for Linux. > > Also see https://www.akkadia.org/drepper/dsohowto.pdf. I'm not sure if the further search of already loaded libraries is harmful or not, but Drepper's spec is not a standard we implement in musl. It's certainly open to discussion but it's the type of behavior that can easily have unforseen and bad consequences, and I would not want to be hasty/sloppy about adopting it. Rich
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