Intel(R) Fortran Compiler for Linux* Systems User's Guide Volume I ...

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Intel® Fortran Compiler for Linux* Systems User's Guide Volume I: Building Applications CHARACTER*(*) string END INTERFACE The C routine must expect two arguments: void pass_str (char *string, unsigned int length_arg ) This interface handles the hidden-length argument, but you must still reconcile C strings that are null-terminated and Fortran strings that are not. In addition, if the data assigned to the Fortran string is less than the declared length, the Fortran string will be blank padded. Rather than trying to handle these string differences in your C routines, the best approach in Fortran/C mixed programming is to adopt C string behavior whenever possible. Fortran functions that return a character string using the syntax CHARACTER*(*) place a hidden string argument and the length of the string at the beginning of the argument list. C functions that implement such a Fortran function call must declare this hidden string argument explicitly and use it to return a value. The C return type should be void. However, you are more likely to avoid errors by not using characterstring return functions. Use subroutines or place the strings into modules or global variables whenever possible. Returning Character Data Types If a Fortran program expects a function to return data of type CHARACTER, the Fortran compiler adds two additional arguments to the beginning of the called procedure's argument list: • The first argument is a pointer to the location where the called procedure should store the result. • The second is the maximum number of characters that must be returned, padded with white spaces if necessary. The called routine must copy its result through the address specified in the first argument. Example that follows shows the Fortran code for a return character function called MAKECHARS and corresponding C routine. Example of Returning Character Types from C to Fortran Fortran code CHARACTER*10 CHARS, MAKECHARS 210
Intel® Fortran Compiler for Linux* Systems User's Guide, Volume I: Building Applications DOUBLE PRECISION X, Y CHARS = MAKECHARS( X, Y ) Corresponding C Routine void makechars ( result, length, x, y ); char *result; int length; double *x, *y; { ...program text, producing returnvalue... for (i = 0; i < length; i++ ) { result[i] = returnvalue[i]; } } In the above example, the following restrictions and behaviors apply: • The function's length and result do not appear in the call statement; they are added by the compiler. • The called routine must copy the result string into the location specified by result; it must not copy more than length characters. • If fewer than length characters are returned, the return location should be padded on the right with blanks; Fortran does not use zeros to terminate strings. • The called procedure is type void. • You must use lowercase names for C routines and INTERFACE blocks to make the calls using lower case. Handling User-Defined Types Fortran 95/90 supports user-defined types (data structures similar to C structures). User-defined types can be passed in modules and common blocks just as other data types, but the other language must know the type's structure. For example: Fortran Code: TYPE LOTTA_DATA SEQUENCE REAL A INTEGER B CHARACTER(30) INFO COMPLEX CX CHARACTER(80) MOREINFO END TYPE LOTTA_DATA TYPE (LOTTA_DATA) D1, D2 COMMON /T_BLOCK/ D1, D2 211
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Intel(R) Fortran Compiler for Linux
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Table Of Contents Table Of Contents
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Table Of Contents Predefined Prepro
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Table Of Contents -e90 or -e95 ....
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Table Of Contents -[no]fpconstant .
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Table Of Contents -noinclude ......
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Table Of Contents -par_threshold n.
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Table Of Contents Using Debugger Co
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Table Of Contents Limitations of Nu
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Table Of Contents Specifiers for Fi
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Table Of Contents Programming with
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Table Of Contents Run-Time Message
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About the Intel® Fortran Compiler
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Intel® Fortran Compiler for Linux*
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Page 183 and 184: Intel® Fortran Compiler for Linux*
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Index ! !DEC$ prefix ..............
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Index -assume dummy_aliases compile
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Index common blocks allocating ....
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Index compiler option -convert meth
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Index additional...................
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Index file information OPEN stateme
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Index FOR$IOS_FLTOVF error message
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Index FOR$IOS_TOOMANREC error messa
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Index -fvisibility-keyword compiler
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Index -ip_no_pinlining compiler opt
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Index manuals additional...........
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Index -nus compiler option.........
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Index -pad_source compiler option..
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Index record characteristics OPEN s
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Index signal routine calling ......
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Index uninstall.sh file ...........
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Intel(R) Fortran Compiler for Linux* Systems User's Guide Volume I ...

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