Because -nostdlib currently has priority over -pthread, libtool can't build
shared C++ libraries using libpthread. A libtool maintainer told me to file a
bug with GCC. Here's my original email:
-------------------------------------------------------
Subject: C++ shared library with pthread missing symbols
From: Simon Perreault <[EMAIL PROTECTED]>
To: libtool@gnu.org
Why does this create a library with missing symbols?
$ cat testcase.cpp
#include <pthread.h>
void f() { pthread_create(0,0,0,0); }
$ libtool --mode=compile g++ -pthread -c testcase.cpp
mkdir .libs
g++ -pthread -c testcase.cpp -fPIC -DPIC -o .libs/testcase.o
g++ -pthread -c testcase.cpp -o testcase.o >/dev/null 2>&1
$ libtool --mode=link g++ -pthread -rpath /usr/local/lib testcase.lo -o
libtestcase.la
g++ -shared -nostdlib /usr/lib/gcc/i386-redhat-linux/4.1.0/../../../crti.o
/usr/lib/gcc/i386-redhat-linux/4.1.0/crtbeginS.o .libs/testcase.o
-L/usr/lib/gcc/i386-redhat-linux/4.1.0
-L/usr/lib/gcc/i386-redhat-linux/4.1.0/../../.. -lstdc++ -lm -lc -lgcc_s
/usr/lib/gcc/i386-redhat-linux/4.1.0/crtendS.o
/usr/lib/gcc/i386-redhat-linux/4.1.0/../../../crtn.o -pthread -Wl,-soname
-Wl,libtestcase.so.0 -o .libs/libtestcase.so.0.0.0
(cd .libs && rm -f libtestcase.so.0 && ln -s libtestcase.so.0.0.0
libtestcase.so.0)
(cd .libs && rm -f libtestcase.so && ln -s libtestcase.so.0.0.0 libtestcase.so)
ar cru .libs/libtestcase.a testcase.o
ranlib .libs/libtestcase.a
creating libtestcase.la
(cd .libs && rm -f libtestcase.la && ln -s ../libtestcase.la libtestcase.la)
$ ldd -r .libs/libtestcase.so
undefined symbol: pthread_create (.libs/libtestcase.so)
linux-gate.so.1 => (0x00799000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x003a3000)
libm.so.6 => /lib/libm.so.6 (0x00b89000)
libc.so.6 => /lib/libc.so.6 (0x00cc7000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x008b1000)
/lib/ld-linux.so.2 (0x00531000)
$ g++ --version
g++ (GCC) 4.1.0 20051212 (Red Hat 4.1.0-0.7)
$ libtool --version
ltmain.sh (GNU libtool) 1.5.20 (1.1220.2.287 2005/08/31 18:54:15)
Thanks!
---------------------------------------------------------------
Here's the reply:
Subject: Re: C++ shared library with pthread missing symbols
From: Ralf Wildenhues <[EMAIL PROTECTED]> (Department of Numerical
Simulation, University of Bonn)
I believe pecause -nostdlib will cause gcc not to add -lpthread even if
-pthread is given. Could you file a bug with the GCC bugzilla (to
either fix the semantics or adjust the documentation)? Thanks.
It may not be trivial to work around within libtool. You can
probably LDFLAGS=-lpthread to work around in your special case.
--
Summary: -pthread should have priority over -nostdlib
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: nomis80 at nomis80 dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25460
