External names & underscores

[gstern]

We are planning to switch to Intel Fortran for Linux. Our product consists of more than 10,000 files, Fortran, C and C++. On each UNIX platform, we are using Fortran compiler options to avoid appending undersores to external names, subroutines, functions and common blocks, in order to have the same access to these names from C/C++ across platforms. Intel's compiler option -nus however only suppresses underscores in subroutine and function names while common block names are still having underscores. Is there a hidden option to suppress underscores in common block names ? Does anyone know if subsequent compiler releases will allow suppression of all underscores, or do I have to change hundreds of source files ?

[Martyn_C_Intel]

I don't know of a command line option to do this. A colleague suggests:

"Consider the following example:
COMMON /MINE/ A,B,C
A = 3.0
END

If you compile this normally, ifc com.f90

you'll get a global symbol called mine_ that represents the COMMON block. As stated, compiling with -nus, does not change this. However, if we change the program and add:
COMMON /MINE/ A,B,C
!DIR$ATTRIBUTES C ::/MINE/
A = 3.0
END

then the global symbol emitted for the COMMON block is just mine.

This does involve changing source, but if the common block declaration is in an include file, as many people do, it's not too onerous. Otherwise, the directive would have to be inserted at each declaration of the common block."

If you feel that this is not sufficient, and a command line option is needed, I encourage you to submit a feature request to Intel Premier Support at https:premier.intel.com (one way to get an account, if you don't have one, is when you download an evaluation compiler). I can't say whether or not this would be accepted, but it seems like a reasonable suggestion/request to make.

Martyn

[Martyn_C_Intel]

Oops, the syntax should be
!DEC$ATTRIBUTES C ::/MINE/
not
!DIR$ATTRIBUTES C ::/MINE/

The rule is !DIR$ for directives but !DEC$ for attributes

Martyn

[joseph-krahn]

If you don't want to go through the code adding directives to the common block definitions, it is not that hard to define CPP macros in a common C header to modify names on the C side of the interface, assuming that all common block names are global names that don't conflict with other local names.

I quickly hacked together this example command-line to build CPP #defines from Fortran sources:

$ grep -i "^ *common */" *.f *.f90 *.inc | awk -F / '{print tolower($2)}' | sort | uniq | awk '{printf "#define %s %s_ ",$1,$1;}'

[Steven_L_Intel1]

madmjcorden:

The rule is !DIR$ for directives but !DEC$ for attributes

This is an old thread resurrected, but the compiler treats !DIR$ and !DEC$ (and !MS$) identically. We document !DEC$ as the prefix but you can use the others if you like.