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opalc++(1)                         Open PAL                         opalc++(1)




NAME

       opalc++ -- Open PAL C++ wrapper compiler


SYNTAX

       opalc++ [-showme|-showme:compile|-showme:link] ...


OPTIONS

       -showme
              Do  not  invoke the underlying compiler.  Instead, show the com-
              mand line that would be executed to compile the program.   NOTE:
              If  a  non-filename  argument is passed on the command line, the
              -showme option will not display any additional flags.  For exam-
              ple,  both "opalc++ --showme" and "opalc++ --showme my_source.c"
              will show all the wrapper-supplied flags.  But "opalc++  -showme
              -v" will only show the underlying compiler name and "-v".

       -showme:compile
              Do  not  invoke  the underlying C++ compiler.  Instead, show the
              compiler flags that would be supplied to the C++ compiler.

       -showme:link
              Do not invoke the underlying C++ compiler.   Instead,  show  the
              linker flags that would be supplied to the C++ compiler.

       See  the  man  page for your underlying compiler for other options that
       can be passed through opalc++


DESCRIPTION

       Conceptually, the role of these commands is quite simple: transparently
       add  relevant compiler and linker flags to the user's command line that
       are necessary to compile / link Open PAL programs, and then invoke  the
       underlying compiler to actually perform the command.

       As such, these commands are frequently referred to as "wrapper" compil-
       ers because they do not actually compile  or  link  applications  them-
       selves;  they  only  add  in command line flags and invoke the back-end
       compiler.

   Background
       Open MPI is comprised of three software  layers:  OPAL  (Open  Portable
       Access  Layer),  ORTE (Open Run-Time Environment), and OMPI (Open MPI).
       There are wrapper compilers for each layer; each layer's  wrapper  only
       links  in  the  libraries  relevant for that layer.  Specifically, each
       layer provides the following wrapper compilers:

       OPAL
           opalcc and opalc++

       ORTE
           ortecc and ortec++

       OMPI
           mpicc, mpic++, mpicxx, mpiCC (only on  systems  with  case-senstive
           file  systems),  mpif77, and mpif90.  Note that mpic++, mpicxx, and
           mpiCC all invoke the same underlying C++  compiler  with  the  same
           options.   All  are provided as compatibility with other MPI imple-
           mentations.

       The Fortran wrapper compilers for MPI (mpif77 and mpif90) will be inop-
       erative and will return an error on use if Fortran 77 / Fortran 90 sup-
       port was not built into the MPI layer.

   Overview
       opalc++ is a convenience wrappers  for  the  underlying  C++  compiler.
       Translation  of  an  Open  PAL program requires the linkage of the Open
       PAL-specific libraries which may not reside  in  one  of  the  standard
       search  directories  of ld(1).  It also often requires the inclusion of
       header files what may also not be found in a standard location.

       opalc++ passes its arguments to the underlying C++ compiler along  with
       the -I, -L and -l options required by Open PAL programs.

       The  Open  PAL  Team  strongly  encourages  using the wrapper compilers
       instead of attempting to link to the Open PAL libraries manually.  This
       allows  the specific implementation of Open PAL to change without forc-
       ing changes to linker directives in users' Makefiles.  Indeed, the spe-
       cific  set of flags and libraries used by the wrapper compilers depends
       on how Open PAL was configured and built; the values can change between
       different installations of the same version of Open PAL.

       Indeed, since the wrappers are simply thin shells on top of an underly-
       ing compiler, there are very, very few compelling reasons  not  to  use
       opalc++.   When  it  is  not possible to use the wrappers directly, the
       -showme:compile and -showme:link options should be  used  to  determine
       what flags the wrappers would have used.  For example:

       shell$ cc -c file1.c `mpicc -showme:compile`

       shell$ cc -c file2.c `mpicc -showme:compile`

       shell$ cc file1.o file2.o `mpicc -showme:link` -o my_mpi_program


NOTES

       It is possible to make the wrapper compilers multi-lib aware.  That is,
       the libraries and includes specified may differ based on  the  compiler
       flags  specified  (for example, with the GNU compilers on Linux, a dif-
       ferent library path may be used if  -m32  is  seen  versus  -m64  being
       seen).   This  is not the default behavior in a standard build, but can
       be activated (for example, in a binary package providing both 32 and 64
       bit support).  More information can be found at:

         https://svn.open-mpi.org/trac/ompi/wiki/compilerwrapper3264


FILES

       The  string  that  the  wrapper  compilers insert into the command line
       before invoking the underlying compiler are stored in a text file  cre-
       ated  by  Open  PAL and installed to $pkgdata/opalc++-wrapper-data.txt,
       where $pkgdata is typically $prefix/share/openmpi, and $prefix  is  the
       top installation directory of Open PAL.

       It  is  rarely  necessary  to edit this file, but it can be examined to
       gain insight into what flags the wrappers are placing  on  the  command
       line.


ENVIRONMENT VARIABLES

       By default, the wrappers use the compilers that were selected when Open
       PAL was configured.  These compilers were either found automatically by
       Open  MPI's "configure" script, or were selected by the user in the CC,
       CXX, F77,  and/or  FC  environment  variables  before  "configure"  was
       invoked.   Additionally,  other  arguments specific to the compiler may
       have been selected by configure.

       These values can be selectively overridden by either editing  the  text
       files  containing  this  configuration  information (see the FILES sec-
       tion), or  by  setting  selected  environment  variables  of  the  form
       "OPAL_value".

       Valid value names are:

       CPPFLAGS
              Flags added when invoking the preprocessor (C or C++)

       LDFLAGS
              Flags added when invoking the linker (C, C++, or Fortran)

       LIBS   Libraries added when invoking the linker (C, C++, or Fortran)

       CC     C compiler

       CFLAGS C compiler flags

       CXX    C++ compiler

       CXXFLAGS
              C++ compiler flags

       F77    Fortran 77 compiler

       FFLAGS Fortran 77 compiler flags

       FC     Fortran 90 compiler

       FCFLAGS
              Fortran 90 compiler flags



OPAL                               Open PAL                         opalc++(1)

opalc++ 1.2.7 - Generated Sat Sep 13 08:04:05 CDT 2008
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