Re: ./configure errors witn musl-gcc (zlib library conflict when building openssh)

[Rich Felker <dalias@libc.org>]

On Fri, Aug 05, 2016 at 06:32:14PM -0400, Assaf Gordon wrote:
> Hello,
> 
> I'm trying to build openssh on Ubuntu with musl-gcc, and encountered a problem during "./configure" due to required library (zlib) which causes conflicts between the system's glibc and musl-libc.
> 
> There is probably a simple solution, but I couldn't find one.
> 
> The system is Ubuntu 14.04 LTS, gcc 4.8.4.
> musl is 1.1.15 built from source, installed to /usr/local/musl .
> 
> First, I build zlib using musl-gcc:
> 
>      wget http://zlib.net/zlib-1.2.8.tar.gz
>      tar -xf zlib-1.2.8.tar.gz
>      cd zlib-1.2.8
>      CC=musl-gcc ./configure
>      make
> 
> This works well (note I did not install it with 'sudo make install').
> 
> Second, I try to build openssh:
> 
>     git clone https://github.com/openssh/openssh-portable
>     cd openssh-portable
>     autoreconf -if
>     CC=musl-gcc ./configure --without-stackprotect --with-zlib=/home/ubuntu/sources/zlib-1.2.8
> But this fails with:
> 
>     checking zlib.h usability... yes
>     checking zlib.h presence... yes
>     checking for zlib.h... yes
>     checking for deflate in -lz... yes
>     checking for possibly buggy zlib... yes
>     configure: error: *** zlib too old - check config.log ***
>     Your reported zlib version has known security problems.  It's possible your
>     vendor has fixed these problems without changing the version number.  If you
>     are sure this is the case, you can disable the check by running
>     "./configure --without-zlib-version-check".
>     If you are in doubt, upgrade zlib to version 1.2.3 or greater.
>     See http://www.gzip.org/zlib/ for details.
> 
> The problem is not that zlib is "too old", but that the wrong shard-object is used (it uses the system's one).
> From config.log:
> 
>     configure:9002: checking for possibly buggy zlib
>     configure:9041: musl-gcc -o conftest -g -O2 -Wall -Wpointer-arith -Wuninitialized -Wsign-compare -Wformat-security -Wsizeof-pointer-memaccess -Wno-pointer-sign -Wno-unused-result -fno-strict-aliasing -D_FORTIFY_SOURCE=2 -ftrapv -fno-builtin-memset -I/home/ubuntu/sources/zlib-1.2.8  -L/home/ubuntu/sources/zlib-1.2.8  -Wl,-z,relro -Wl,-z,now -Wl,-z,noexecstack conftest.c -lz  >&5
>     configure:9041: $? = 0
>     configure:9041: ./conftest
>     Error relocating /lib/x86_64-linux-gnu/libz.so.1: __snprintf_chk: symbol not found
>     Error relocating /lib/x86_64-linux-gnu/libz.so.1: __vsnprintf_chk: symbol not found
>     configure:9041: $? = 127
>     configure: program exited with status 127

Somehow musl-gcc is not correctly replacing the compiler's builtin
library path. It's likely something weird Ubuntu's gcc build is doing
for their multilib/multiarch support, but hard to say specifically
what. Can you build a hello world program succesfully? What does
musl-gcc -v hello.c say, given a hello world program hello.c?

Rich