[mpich2-dev] wrapping library calls

[Rob Latham]

Hey folks

Phil's put together this slick tool called 'darshan'[1].  Darshan
uses the MPI profiling interface to wrap MPI calls, and linker tricks
(-wrap) to wrap posix I/O calls.

We have to modify the MPI wrapper scripts so that darshan's
implementation of the wrapped symbols gets linked in.  Each driver
update requires a new set of wrapper shell scripts.

Is there some way through the command line that we can pass the flags
'-Wl,-wrap,read,-wrap,write,...' and '-L/path/to/darshan
-ldarshan-posix'  ?  

What would be great is if darshan could ship an mpicc wrapper that was
just one line "/path/to/real/mpicc -Wl,-wrap,read,-wrap,write... $@
-L/path/to/darshan -ldarshan-io".  

Unfortunately when I try this, the -Wl and -L flags I pass in go in
very early in the generated command line ("${allargs[@]}" ).  

Phil wrote a script to take the output of 'mpicc -show' and munge the
command line accordingly, so this is kind of a solved problem for
Darshan.  I was just wondering if there was an approach I had not
considered in case we want to wrap function calls for some other
project in the future.

[1]http://press.mcs.anl.gov/darshan/

Thanks
==rob

-- 
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA