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Date: Sat, 27 Jun 2015 11:41:43 +0200
From: "piranna@...il.com" <piranna@...il.com>
To: musl@...ts.openwall.com
Subject: Re: Link problems with static node-canvas

Hi Lynx, thank you for your answer.

Attached you can find the output of `readelf -Wa canvas.node`, as you
can see the only NEEDED libraries are libstdc++.so.6 (the gcc c++
runtime) and libc.so (musl, in this case). Also you can see that
jinit_arith_decoder has entries in the .rela.plt, .dynsym and .symtab
sections.

I've compiled canvas.node with the -static argument to force all its
dependencies are linked statically and "bundled" in the final shared
object. GCC devs don't want -shared and -static being used at the same
time and try to promote the usage of dynamic libraries everywhere
(https://bugzilla.redhat.com/show_bug.cgi?id=214465#c1) although they
are compatible and has some valid use cases (like generating Node.js
modules, that's this case), and although both files are the same
crtbeginT.o (used when the -static flag is enabled) is not compiled
with -fPIL needed to be used in shared libraries, so I needed to write
crtbeginS.o over crtbeginT.o
(https://bugs.launchpad.net/ubuntu/+source/gcc-4.4/+bug/640734/comments/6).
LLVM don't have this problem, since it only have one version of
crtbegin.o, in any case this seems not to be a problem since I have
done the sabe "trick" both on my Ubuntu machine and the NodeOS
toolchain and nothing more got broken...

If you want to try it yourself, you can download the code of my fork
of node-canvas (https://github.com/NodeOS/node-canvas) and compile it
with 'npm install --has_cairo=false' (you'll need to have Node.js
installed)

2015-06-27 8:18 GMT+02:00 Рысь <lynx@...server.ru>:
> On Sat, 27 Jun 2015 01:06:04 +0200
> "piranna@...il.com" <piranna@...il.com> wrote:
>
>> I have been trying in the last days to craft a statically linked
>> version of node-canvas (https://github.com/Automattic/node-canvas) to
>> use it in NodeOS (a musl-based Linux OS with no global libraries).
>>
>> In my fork I managed to convert it from needing cairo, libjpeg,
>> freetype and giflib as dynamica libraries to create it as a statically
>> linked shared object that contains all of them inside, making it
>> autonomous (that's the way ideally Node.js addons are build, as .so
>> files -with the extension changed to .node- with all their
>> dependencies statically linked and not needing any dynamic library.
>> This .node files later are loaded with dlopen() when someone requires
>> them by calling the require() function from inside Node.js).
>>
>> When compiling it in Ubuntu using glibc it works correctly, but when
>> compiling it for NodeOS using musl, I got an error about "Error
>> relocating: jinit_arith_decode symbol not found"
>> (https://github.com/Automattic/node-canvas/issues/551#issuecomment-114253760).
>> That function is from libjpeg, and both the jpeg.a and the canvas.node
>> files have references to it. I've trying to use the musl-compiled
>> canvas.node file by using LD_LIBRARY_PATH and it shows the "Error
>> relocating" string, but doesn't clarify where's the error. At first I
>> though it would be a libjpeg-turbo problem, but after removing the
>> support for JPEG in node-canvas, the same "Error relocating" problem
>> showed, only that now regarding to a FreeType function, so since it
>> works correctly with glibc that's why I thought it could be a linking
>> problem related to musl. This is strange since other compiled modules
>> works correctly under NodeOS, but it's true they don't link with other
>> libraries (both startic or dynamic) beyond the C lib or the Linux
>> kernel SysCalls... :-/
>>
>> Any idea or suggestiong about what could be the culprit or where to
>> continue investigating?
>>
>
> If canvas.node is a shared object then linker will not warn you about
> any missing symbols when making it. So, your libjpeg.a was not included
> during build or somehow broken. Do a `readelf -Wa canvas.node` and make
> sure you still have no shared dependencies on libraries you link
> statically (you have no NEEDED libraries in Dynamic section).
> Alternatively gzip the output and attach with your next message.



-- 
"Si quieres viajar alrededor del mundo y ser invitado a hablar en un
monton de sitios diferentes, simplemente escribe un sistema operativo
Unix."
– Linus Tordvals, creador del sistema operativo Linux

Download attachment "canvas_node.txt.tar.gz" of type "application/x-gzip" (146897 bytes)

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