Re: order of -L options created by gcc for the linker

Andrew Haley-5 wrote:

tjevon writes:
 >
 > I'm having a problem with gcc placing the default gcc libraries
 > (-L/usr/lib/gcc/x86_64-redhat-linux/3.4.5) ahead of the correct (newer)
 > versions in the list of arguments being passed to ld.
 >
 
This doesn't make any sense.  gcc always links the versions of the
libraries that are compatible with the gcc version that's installed.
If you have a newer version of gcc installed, with newer libraries,
the new gcc will link against the new libraries.

I find it hard to imagine what kind of a broken setup would give the
problems you're describing.

Andrew

Maybe I should have been more specific about which libraries I'm having trouble with. There is a version of gtk+ that is part of the linux (redhat) distribution installed in /usr/lib64. There is a more recent version available that I installed in /usr/local/ext/lib.

The problem I'm having isn't directly caused by my installation or my build environment. The problem is that when gcc formats the line used by ld, it's placing -L/usr/lib/gcc/x86_64-redhat-linux/3.4.5/../../../../lib64 before the -L/usr/local/extlib that I pass to the gcc (using -Wl,) for the link. As a result, the incorrect gtk+ library is being used for the link.

so the command that my build environment executes is similar to:
/usr/bin/g++ foo.o -o foo -Wl,-R/usr/local/ext/lib -Wl,-L/usr/local/ext/lib -Wl,-R/usr/X11R6/lib64 -Wl,-L/usr/X11R6/lib64 -lgtkmm ... -lgtk-x11-2.0 ...

I left out all the other require libraries for brevity.

The line that g++ creates for the link has -L/usr/lib/gcc/x86_64-redhat-linux/3.4.5/../../../../lib64 (location not specified by me, but by gcc) before the -L/usr/local/ext/lib. I determined this by adding a -v argument.

If I change the line passed to g++ to: (please notice that I've removed the -Wl, preceeding my lib location)
/usr/bin/g++ foo.o -o foo -Wl,-R/usr/local/ext/lib -L/usr/local/ext/lib -Wl,-R/usr/X11R6/lib64 -Wl,-L/usr/X11R6/lib64 -lgtkmm ... -lgtk-x11-2.0 ...

the line that g++ creates for the link has -L/usr/local/ext/lib before the gcc generated -L/usr/lib/gcc/x86_64-redhat-linkux/3.4.5/../../../../lib64.

What I was surprised at was the resultant different location in the link command for my -L/usr/local/ext/lib as a result of using -Wl,. I was looking for an explaination of this behavior and/or a way to insure that my -L would preceed any -L inserted into the link command by gcc.

The obvious way would be to just use the -L instead of -Wl. Unfortunately, this is where my build environment enters the picture. There is currently (may need to change) no way to have it generate a -L instead of the -Wl,-L.

After rereading my original, I realize I should have said "problem with gcc placing the default gcc library locations (-L(s)), ahead of my specified -L.

tjevon