libstdc++/5859: gdb fails to break in C++ MPI code

[cummings at cacr dot caltech dot edu]

>Number:         5859
>Category:       libstdc++
>Synopsis:       gdb fails to break in C++ MPI code
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Mar 06 19:06:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Julian Cummings
>Release:        3.0
>Organization:
>Environment:
i686 running Linux 2.4.9-ac9
>Description:
The gdb debugger fails to break on the symbol MPI_Init
in a trivial MPI code written in C++.  The code uses the
mpich package from Argonne National Laboratory and is 
compiled using mpiCC, a script that invokes the g++ compiler
and links with libmpich.a.  The code is executed using 
"mpirun" and the -gdb flag, which causes gdb to set a 
breakpoint at MPI_Init and run the program.  

The problem is triggered by any C++ MPI code that utilizes 
C++ streams, for example, to write something to std::cout.
In this case, the code will run through all of main() and
stop inside the global object destructor phase.  With no
usage of C++ streams, the code halts at MPI_Init as it 
should.  Also, a comparable MPI code written in C functions
properly with gdb.

I am reporting this as a gcc bug because it does not happen
with gcc 2.96.  It seems that something has changed with
respect to the C++ standard library and streams that makes
debugging of MPI codes with gdb no longer possible.  
>How-To-Repeat:
You will need to have a recent version of mpich
installed (http://www.mcs.anl.gov/mpi/mpich).  I am using 
mpich-1.2.1.  With this installed, build my example code
with the command "mpiCC -g -o cctest main.cc".  Then run it
on a single processor, for example, with the command
"mpirun -np 1 ./cctest".  Now try to run it under the gdb
debugger by adding the flag -gdb to the mpirun command.
You should see that the code does not break at MPI_Init
as expected.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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