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SYNTAX
oshcc [--showme | --showme:compile | --showme:link] ...
oshcxx [--showme | --showme:compile | --showme:link] ...
oshc++ [--showme | --showme:compile | --showme:link] ...
oshfort [--showme | --showme:compile | --showme:link] ...
shmemcc [--showme | --showme:compile | --showme:link] ...
shmemcxx [--showme | --showme:compile | --showme:link] ...
shmemc++ [--showme | --showme:compile | --showme:link] ...
shmemfort [--showme | --showme:compile | --showme:link] ...
OPTIONS
The options below apply to all of the wrapper compilers:
• --showme: This option comes in several different variants (see below). None of the variants invokes the
underlying compiler; they all provide information on how the underlying compiler would have been
invoked had --showme not been used. The basic --showme option outputs the command 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 example, both "oshcc --showme and oshcc --showme my_source.c will show all the
wrapper-supplied flags. But oshcc --showme -v will only show the underlying compiler name and -v.
• --showme:compile: Output the compiler flags that would have been supplied to the underlying compiler.
• --showme:link: Output the linker flags that would have been supplied to the underlying compiler.
• --showme:command: Outputs the underlying compiler command (which may be one or more tokens).
• --showme:incdirs: Outputs a space-delimited (but otherwise undecorated) list of directories that the
wrapper compiler would have provided to the underlying compiler to indicate where relevant header files
are located.
• --showme:libdirs: Outputs a space-delimited (but otherwise undecorated) list of directories that the
wrapper compiler would have provided to the underlying linker to indicate where relevant libraries are
located.
• --showme:libs Outputs a space-delimited (but otherwise undecorated) list of library names that the
wrapper compiler would have used to link an application. For example: mpi open-pal util.
• --showme:version: Outputs the version number of Open MPI.
• --showme:help: Output a brief usage help message.
See the man page for your underlying compiler for other options that can be passed through oshcc.
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 OpenSHMEM programs, and then invoke
the underlying compiler to actually perform the command.
As such, these commands are frequently referred to as “wrapper” compilers because they do not actually
compile or link applications themselves; they only add in command line flags and invoke the back-end
compiler.
BACKGROUND
Open MPI provides wrapper compilers for several languages:
• oshcc, shmemcc: C
• oshc++, oshcxx, shmemc++, shmemcxx`:: C++
• oshfort, shmemfort: Fortran
The wrapper compilers for each of the languages are identical; they can be use interchangeably. The
different names are provided solely for backwards compatibility.
FORTRAN NOTES
The Fortran wrapper compiler for OpenSHMEM (oshfort and shmemfort) can compile and link OpenSHMEM
applications that use any/all of the OpenSHMEM Fortran bindings.
Note, however, that the Fortran compiler may require additional command-line options to enforce a
specific Fortran dialect. For example, in some versions of the IBM XLF compiler, if xlf90 is the
underlying Fortran compiler, -qfixed may be necessary to compile fixed-format Fortran source files.
Finally, note that oshfort will be inoperative and will return an error on use if Fortran support was not
built into the OpenSHMEM layer.
OVERVIEW
oshcc and shmemcc are convenience wrappers for the underlying C compiler. Translation of an OpenSHMEM
program requires the linkage of the OpenSHMEM-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.
oshcc and shmemcc pass their arguments to the underlying C compiler along with the -I, -L and -l options
required by OpenSHMEM programs.
The same is true for all the other language wrapper compilers.
The OpenSHMEM Team strongly encourages using the wrapper compilers instead of attempting to link to the
OpenSHMEM libraries manually. This allows the specific implementation of OpenSHMEM to change without
forcing changes to linker directives in users’ Makefiles. Indeed, the specific set of flags and libraries
used by the wrapper compilers depends on how OpenSHMEM was configured and built; the values can change
between different installations of the same version of OpenSHMEM.
Indeed, since the wrappers are simply thin shells on top of an underlying compiler, there are very, very
few compelling reasons not to use oshcc. 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 `shmemcc --showme:compile`
shell$ cc -c file2.c `shmemcc --showme:compile`
shell$ cc file1.o file2.o `shmemcc --showme:link` -o my_oshmem_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 different 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 here.
FILES
The strings that the wrapper compilers insert into the command line before invoking the underlying
compiler are stored in a text file created by OpenSHMEM and installed to $pkgdata/NAME-wrapper-data.txt,
where:
• $pkgdata is typically $prefix/share/openmpi
• $prefix is the top installation directory of OpenSHMEM
• NAME is the name of the wrapper compiler (e.g., $pkgdata/shmemcc-wrapper-data.txt)
It is rarely necessary to edit these files, but they 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 OpenSHMEM was configured. These
compilers were either found automatically by Open MPI’s “configure” script, or were selected by the user
in the CC, CXX, 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 section), or by setting selected environment variables of the form
oshmem_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
• FC: Fortran compiler
• FCFLAGS: Fortran compiler flags
COPYRIGHT
2003-2025, The Open MPI Community
Feb 17, 2025 OSHMEM-WRAPPER-COMPILER(1)