Bug#794798: libnspr4-dev: pthread missing from pkg-config lib

[Mike Hommey]

On Wed, Apr 20, 2016 at 09:05:11AM -0400, Peter Jones wrote:
> > Mike Hommey wrote:
> > > On Thu, Aug 06, 2015 at 04:37:06PM -0500, D. Jared Dominguez wrote:
> > >> On Thu, Aug 06, 2015 at 03:46:39PM -0500, Mike Hommey wrote:
> > >> >On Thu, Aug 06, 2015 at 01:42:55PM -0500, Daniel Jared Dominguez wrote:
> > >> >>Package: libnspr4-dev
> > >> >>Version: 2:4.10.8-2
> > >> >>Severity: important
> > >> >>
> > >> >>"pkg-config --libs nspr" returns:
> > >> >>-lplds4 -lplc4 -lnspr4
> > >> >>
> > >> >>However, at least pthread is missing, which causes building with nspr4 and
> > >> >>using pkg-config not to work right.
> > >> >
> > >> >You don't need to link against pthread to link against nspr.
> > >>
> > >> Well, it's what's causing this: http://paste.debian.net/289831/
> > >>
> > >> Particularly,
> > >> """
> > >> /usr/bin/gcc -g -O2 -fstack-protector-strong -Wformat
> > >> -Werror=format-security  -Wall -Wsign-compare -Wno-unused-result
> > >> -Wno-unused-function -std=gnu11 -fshort-wchar -fPIC -flto
> > >> -fno-strict-aliasing -fno-merge-constants -D_GNU_SOURCE -DCONFIG_x86_64
> > >> -I/«PKGBUILDDIR»/include     -I/usr/include/efivar -I/usr/include/nss
> > >> -I/usr/include/nspr   -Wl,-z,relro    -D_FORTIFY_SOURCE=2 -o pesigcheck
> > >> pesigcheck.o pesigcheck_context.o certdb.o cms_common.o content_info.o oid.o
> > >> password.o signed_data.o signer_info.o wincert.o ucs2.o
> > >> /«PKGBUILDDIR»/libdpe/libdpe.a  -lefivar -lnss3 -lnssutil3 -lsmime3 -lssl3
> > >> -lplds4 -lplc4 -lnspr4 -lpopt /usr/bin/ld: /tmp/ccSnL8H8.ltrans1.ltrans.o:
> > >> undefined reference to symbol 'pthread_rwlock_wrlock@@GLIBC_2.2.5'
> > >> //lib/x86_64-linux-gnu/libpthread.so.0: error adding symbols: DSO missing from command line
> > >> collect2: error: ld returned 1 exit status
> > >> """
> > >>
> > >> I see that this is what Fedora is doing:
> > >> http://pkgs.fedoraproject.org/cgit/nspr.git/tree/nspr-config-pc.patch
> > >>
> > >> Also,
> > >> $ ldd /usr/lib/x86_64-linux-gnu/libnspr4.so | grep pthread
> > >>         libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f3111be4000)
> > >>
> > >> To me, that seems to be a pretty good indication that pthread is needed to link
> > >> against nspr.
> > >
> > > To me, that seems to be a pretty good indication that one of those
> > > object files is using pthread_rwlock_wrlock.
> > >
> > > The only reference to pthread_rwlock_wrlock in the nspr code base is in
> > > a .c file, which means there is no way something #including nspr header
> > > can inadvertently have a dependency on that symbol.
> > 
> > -lpthread -lrt -ldl (@OS_LIBS@) is certainly required for static linking 
> > (and there are static libraries in libnspr-dev).
> > 
> > (However, I think the linked above fedora patch is also slightly wrong, 
> > @OS_LIBS@ should be in Libs.private, not in Libs).
> > 
> > But I don't see -static in failed command above, so not sure why it 
> > fails and if this is a same problem.
> 
> This doesn't have anything to do with -static, or with header files.
> What's going on is that the dynamic section of libnspr4.so has a
> dependency pointing to libpthread.so.0:
> 
> $ eu-readelf -d /usr/lib/x86_64-linux-gnu/libnspr4.so
> Dynamic segment contains 32 entries:
>  Addr: 0x000000000023ad98  Offset: 0x03ad98  Link to section: [ 4] '.dynstr'
>   Type              Value
>   NEEDED            Shared library: [libpthread.so.0]
>   NEEDED            Shared library: [libdl.so.2]
>   NEEDED            Shared library: [librt.so.1]
>   NEEDED            Shared library: [libc.so.6]
>   SONAME            Library soname: [libnspr4.so]
> ...
> 
> But the linker that gcc gets when it calls /usr/bin/ld defaults to
> having the option flags "--no-add-needed --no-copy-dt-needed-entries"
> set - as I understand this has been a deliberate feature, and library
> packages are supposed to have been fixed to work with[0].  The result is
> that programs or libraries linking against libnspr4.so needs to use
> -lpthreads /as a result of linking against libnspr4.so/.

No they don't.

$ cat <<EOF > test.c
#include <prmem.h>

int main() {
  void *foo = PR_Malloc(42);
  PR_Free(foo);
  return 0;
}
EOF
$ pkg-config nspr --cflags --libs
-I/usr/include/nspr -lplds4 -lplc4 -lnspr4
$ gcc -o test test.c $(pkg-config nspr --cflags --libs)
$ ./test
$ echo $?
0
$ readelf -d test | head

Dynamic section at offset 0x8a8 contains 27 entries:
  Tag        Type                         Name/Value
 0x0000000000000001 (NEEDED)             Shared library: [libplds4.so]
 0x0000000000000001 (NEEDED)             Shared library: [libplc4.so]
 0x0000000000000001 (NEEDED)             Shared library: [libnspr4.so]
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
 0x000000000000000c (INIT)               0x400548
 0x000000000000000d (FINI)               0x400754
 0x0000000000000019 (INIT_ARRAY)         0x600890