How do shared libraries work in a mixed 64bit/32bit system?

Question

Good morning,

on a 64bit RedHat box we have to compile and run a 32bit application. Meanwhile I managed to compile the gcc version needed (4.0.3) and all required runtime libraries in 32bit and have set the LD_LIBRARY_PATH to point to the 32bit versions, but now during the remaining build process, a small java program needs to be executed which is installed in /usr/bin as a 64bit program, which now finds the 32bit version of libgcc_s.so first.

In general, if I set the LD_LIBRARY_PATH to the 32bit versions, I break the 64bit programs and vice versa.

How it this supposed to work at all? I am certain I am not the first person with this problem at hand. How is it solved usually?

Regards, Stefan

Answer 1

As a workaround, wrap the Java call in a small shell script which unsets LD_LIBRARY_PATH and then calls the executable. Alternatively, this might also work:

LD_LIBRARY_PATH= java...

Note the space between "=" and the name of the executable.

Answer 2

On Solaris one can use LD_LIBRARY32_PATH and LD_LIBRARY64_PATH, but that isn't supported on Linux.

In general, you should just never need to set LD_LIBRARY_PATH at all in the first place:

• either install needed libraries into /usr/lib32 or /usr/lib64 as appropriate, or
• build your 32-bit application with -Wl,-rpath=/path/to/32-bit/libs

Answer 3

Just set LD_LIBRARY_PATH to both paths (use colons to delimit). The linker will ignore the libraries that it cannot read.