GDC fails to link with GSL and fortran code

[Johannes Pfau via Digitalmars-d-learn]

Am Tue, 17 Mar 2015 12:13:44 +0000
schrieb "Andrew Brown" <aabrown24 at hotmail.com>:

> Thank you very much for your replies, I now have 2 solutions to 
> my problem! Both compiling on a virtual machine running debian 
> wheezy, and using gcc to do the linking produced executables that 
> would run on the cluster.
> 
> Compiling with the verbose flags for linker and compiler produced 
> the following output:
> 
> failed gdc attempt: http://dpaste.com/0Z5V4PV
> 
> successful dmd attempt: http://dpaste.com/0S5WKJ5
> 
> successful use of gcc to link: http://dpaste.com/0YYR39V
> 
> It seems a bit of a mess, with various libraries in various 
> places. I'll see if I can get to the bottom of it, I think it'll 
> be a learning experience.
> 
> Thanks again for the swift and useful help and guidance.
> 
> Andrew

GCC's verbose output can indeed be quite confusing but if you know
what to look for it's possible to find some useful information :-)

In your case the linker messages hinted at a problem with libc. And as
there were only a few errors it's likely a version compatibility
problem.

If you search for libc.so in these logs you'll find this:
Failed GDC:
attempt to open /usr/lib/../lib64/libc.so succeeded
opened script file /usr/lib/../lib64/libc.so
opened script file /usr/lib/../lib64/libc.so
attempt to open /lib64/libc.so.6 succeeded
/lib64/libc.so.6

GCC:
attempt to
open /software/lib/gcc/x86_64-redhat-linux/4.9.1/../../../../lib64/libc.so
succeeded opened script
file /software/lib/gcc/x86_64-redhat-linux/4.9.1/../../../../lib64/libc.so
opened script
file /software/lib/gcc/x86_64-redhat-linux/4.9.1/../../../../lib64/libc.so
attempt to open /software/lib64/libc.so.6
succeeded /software/lib64/libc.so.6

The binary gdc searches for libaries in the 'usual' places,
including /usr/lib64. Your gcc doesn't search in /usr/lib64 but
in /software. You seem to have an incompatible libc in /usr/lib64
which gets picked up by gdc. This is one reason why binary compiler
releases are difficult to maintain and we usually recommend to compile
gdc from source.

DMD avoids this mess by simply calling the local gcc instead of ld to
link. GCC unfortunately doesn't support this and forces us to always
call the linker directly.