RE: Confused about linking

[lrtaylor at micron dot com]

No, that is not right.  If you look at his file listing, he obviously does have libboost_thread installed.

-lxx causes the linker to look first for libxx.so and then libxx.a, unless you override that default by specifying the appropriate actions.  In this case, with -lboost_thread, it's going to look for libboost_thread.so and then libboost_thread.a.  However, neither of them exists - instead, you have libboost_thread.so.1.  Create a symbolic link in /usr/lib named libboost_thread.so to libboost_thread.so.1, and you should be OK.

For example, execute the following commands:

su (must be logged in as root)
cd /usr/bin
ln -s libboost_thread.so.1 libboost_thread.so

Cheers,
Lyle

-----Original Message-----
From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org] On Behalf Of Ishwar Rattan
Sent: Monday, August 09, 2004 4:51 PM
To: Mattias Brändström
Cc: gcc-help@gcc.gnu.org
Subject: Re: Confused about linking

-lxx

implies that libxx.a exists in the specified path, has nothing
to do with shared libraries. Install libboost-thread first!

-ishwar


On Mon, 9 Aug 2004, [ISO-8859-1] Mattias Brändström wrote:

> Hello!
>
> I am seriously confused when it comes to linking my executable written
> in C++. More specificaly I want to link againts boost_thread and
> boost_regex on a Fedora 2 system.
>
> These files are located in /usr/lib:
>
> /usr/lib/libboost_thread.so.1
> /usr/lib/libboost_thread.so.1.31.0
> /usr/lib/libboost_regex.a
> /usr/lib/libboost_regex.so.1.31.0
> /usr/lib/libboost_regex.so.1
>
> I have a small file named 'foo.cpp' containing the following:
>
> int main()
> {
>    return 0;
> }
>
> When I try the following:
>
> g++ foo.cpp -L/usr/lib -lboost_regex
>
> everthing works fine. But when I do this:
>
> g++ foo.cpp -L/usr/lib -lboost_thread
>
> I get:
>
> /usr/bin/ld: cannot find -lboost_thread
> collect2: ld returned 1 exit status
>
> When removing /usr/lib/libboost_regex.a I get the same error as above
> when trying to 'g++ foo.cpp -L/usr/lib -lboost_regex'.
>
> I was under the impression that g++ would look for shared librarires and
> try to link againt them first and if that didn't work try to link againt
> static libraries. Perhaps this is not tha case? Can someone enlighten me
> on this, probalbly trivial, issue?
>
> Thanks in advance!
>
> :.:: mattias
>
> PS.
>  > g++ -v foo.cpp -L/usr/lib -lboost_thread
>
> Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/specs
> Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
> --infodir=/usr/share/info --enable-shared --enable-threads=posix
> --disable-checking --disable-libunwind-exceptions --with-system-zlib
> --enable-__cxa_atexit --host=i386-redhat-linux
> Thread model: posix
> gcc version 3.3.3 20040412 (Red Hat Linux 3.3.3-7)
>   /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/cc1plus -quiet -v
> -D__GNUC__=3 -D__GNUC_MINOR__=3 -D__GNUC_PATCHLEVEL__=3 -D_GNU_SOURCE
> foo.cpp -D__GNUG__=3 -quiet -dumpbase foo.cpp -auxbase foo -version -o
> /tmp/cccCYtHd.s
> GNU C++ version 3.3.3 20040412 (Red Hat Linux 3.3.3-7) (i386-redhat-linux)
>          compiled by GNU C version 3.3.3 20040412 (Red Hat Linux 3.3.3-7).
> GGC heuristics: --param ggc-min-expand=64 --param ggc-min-heapsize=64549
> ignoring nonexistent directory "/usr/i386-redhat-linux/include"
> #include "..." search starts here:
> #include <...> search starts here:
>   /usr/include/c++/3.3.3
>   /usr/include/c++/3.3.3/i386-redhat-linux
>   /usr/include/c++/3.3.3/backward
>   /usr/local/include
>   /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/include
>   /usr/include
> End of search list.
>   as -V -Qy -o /tmp/ccqqpjhi.o /tmp/cccCYtHd.s
> GNU assembler version 2.15.90.0.3 (i386-redhat-linux) using BFD version
> 2.15.90.0.3 20040415
>   /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/collect2 --eh-frame-hdr -m
> elf_i386 -dynamic-linker /lib/ld-linux.so.2
> /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../../crt1.o
> /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../../crti.o
> /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/crtbegin.o -L/usr/lib
> -L/usr/lib/gcc-lib/i386-redhat-linux/3.3.3
> -L/usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../.. /tmp/ccqqpjhi.o
> -lboost_thread -lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc
> /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/crtend.o
> /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../../crtn.o
> /usr/bin/ld: cannot find -lboost_thread
> collect2: ld returned 1 exit status
>