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GNU Info (autoconf.info)Fortran 77 CompilerFortran 77 Compiler Characteristics ----------------------------------- - Macro: AC_PROG_F77 ([COMPILER-SEARCH-LIST]) Determine a Fortran 77 compiler to use. If `F77' is not already set in the environment, then check for `g77' and `f77', and then some other names. Set the output variable `F77' to the name of the compiler found. This macro may, however, be invoked with an optional first argument which, if specified, must be a space separated list of Fortran 77 compilers to search for. This just gives the user an opportunity to specify an alternative search list for the Fortran 77 compiler. For example, if you didn't like the default order, then you could invoke `AC_PROG_F77' like this: AC_PROG_F77(fl32 f77 fort77 xlf cf77 g77 f90 xlf90) If using `g77' (the GNU Fortran 77 compiler), then `AC_PROG_F77' will set the shell variable `G77' to `yes'. If the output variable `FFLAGS' was not already set in the environment, then set it to `-g -02' for `g77' (or `-O2' where `g77' does not accept `-g'). Otherwise, set `FFLAGS' to `-g' for all other Fortran 77 compilers. - Macro: AC_PROG_F77_C_O Test if the Fortran 77 compiler accepts the options `-c' and `-o' simultaneously, and define `F77_NO_MINUS_C_MINUS_O' if it does not. The following macros check for Fortran 77 compiler characteristics. To check for characteristics not listed here, use `AC_TRY_COMPILE' (Note: Examining Syntax) or `AC_TRY_RUN' (Note: Run Time), making sure to first set the current language to Fortran 77 `AC_LANG(Fortran 77)' (Note: Language Choice). - Macro: AC_F77_LIBRARY_LDFLAGS Determine the linker flags (e.g. `-L' and `-l') for the "Fortran 77 intrinsic and run-time libraries" that are required to successfully link a Fortran 77 program or shared library. The output variable `FLIBS' is set to these flags. This macro is intended to be used in those situations when it is necessary to mix, e.g. C++ and Fortran 77 source code into a single program or shared library (*note Mixing Fortran 77 With C and C++: (automake)Mixing Fortran 77 With C and C++.). For example, if object files from a C++ and Fortran 77 compiler must be linked together, then the C++ compiler/linker must be used for linking (since special C++-ish things need to happen at link time like calling global constructors, instantiating templates, enabling exception support, etc.). However, the Fortran 77 intrinsic and run-time libraries must be linked in as well, but the C++ compiler/linker doesn't know by default how to add these Fortran 77 libraries. Hence, the macro `AC_F77_LIBRARY_LDFLAGS' was created to determine these Fortran 77 libraries. The macro `AC_F77_DUMMY_MAIN' or `AC_F77_MAIN' will probably also be necessary to link C/C++ with Fortran; see below. - Macro: AC_F77_DUMMY_MAIN ([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND]) With many compilers, the Fortran libraries detected by `AC_F77_LIBRARY_LDFLAGS' provide their own `main' entry function that initializes things like Fortran I/O, and which then calls a user-provided entry function named e.g. `MAIN__' to run the user's program. The `AC_F77_DUMMY_MAIN' or `AC_F77_MAIN' macro figures out how to deal with this interaction. When using Fortran for purely numerical functions (no I/O, etcetera), users often prefer to provide their own `main' and skip the Fortran library initializations. In this case, however, one may still need to provide a dummy `MAIN__' routine in order to prevent linking errors on some systems. `AC_F77_DUMMY_MAIN' detects whether any such routine is _required_ for linking, and what its name is; the shell variable `F77_DUMMY_MAIN' holds this name, `unknown' when no solution was found, and `none' when no such dummy main is needed. By default, ACTION-IF-FOUND defines `F77_DUMMY_MAIN' to the name of this routine (e.g. `MAIN__') _if_ it is required. [ACTION-IF-NOT-FOUND] defaults to exiting with an error. In order to link with Fortran routines, the user's C/C++ program should then include the following code to define the dummy main if it is needed: #ifdef F77_DUMMY_MAIN # ifdef __cplusplus extern "C" # endif int F77_DUMMY_MAIN() { return 1; } #endif Note that `AC_F77_DUMMY_MAIN' is called automatically from `AC_F77_WRAPPERS'; there is generally no need to call it explicitly unless one wants to change the default actions. - Macro: AC_F77_MAIN As discussed above for `AC_F77_DUMMY_MAIN', many Fortran libraries allow you to provide an entry point called e.g. `MAIN__' instead of the usual `main', which is then called by a `main' function in the Fortran libraries that initializes things like Fortran I/O. The `AC_F77_MAIN' macro detects whether it is _possible_ to utilize such an alternate main function, and defines `F77_MAIN' to the name of the function. (If no alternate main function name is found, `F77_MAIN' is simply defined to `main'.) Thus, when calling Fortran routines from C that perform things like I/O, one should use this macro and name the "main" function `F77_MAIN' instead of `main'. - Macro: AC_F77_WRAPPERS Defines C macros `F77_FUNC(name,NAME)' and `F77_FUNC_(name,NAME)' to properly mangle the names of C/C++ identifiers, and identifiers with underscores, respectively, so that they match the name-mangling scheme used by the Fortran 77 compiler. Fortran 77 is case-insensitive, and in order to achieve this the Fortran 77 compiler converts all identifiers into a canonical case and format. To call a Fortran 77 subroutine from C or to write a C function that is callable from Fortran 77, the C program must explicitly use identifiers in the format expected by the Fortran 77 compiler. In order to do this, one simply wraps all C identifiers in one of the macros provided by `AC_F77_WRAPPERS'. For example, suppose you have the following Fortran 77 subroutine: subroutine foobar(x,y) double precision x, y y = 3.14159 * x return end You would then declare its prototype in C or C++ as: #define FOOBAR_F77 F77_FUNC(foobar,FOOBAR) #ifdef __cplusplus extern "C" /* prevent C++ name mangling */ #endif void FOOBAR_F77(double *x, double *y); Note that we pass both the lowercase and uppercase versions of the function name to `F77_FUNC' so that it can select the right one. Note also that all parameters to Fortran 77 routines are passed as pointers (Note: Mixing Fortran 77 With C and C++. ). Although Autoconf tries to be intelligent about detecting the name-mangling scheme of the Fortran 77 compiler, there may be Fortran 77 compilers that it doesn't support yet. In this case, the above code will generate a compile-time error, but some other behavior (e.g. disabling Fortran-related features) can be induced by checking whether the `F77_FUNC' macro is defined. Now, to call that routine from a C program, we would do something like: { double x = 2.7183, y; FOOBAR_F77(&x, &y); } If the Fortran 77 identifier contains an underscore (e.g. `foo_bar'), you should use `F77_FUNC_' instead of `F77_FUNC' (with the same arguments). This is because some Fortran 77 compilers mangle names differently if they contain an underscore. - Macro: AC_F77_FUNC (NAME, [SHELLVAR]) Given an identifier NAME, set the shell variable SHELLVAR to hold the mangled version NAME according to the rules of the Fortran 77 linker (see also `AC_F77_WRAPPERS'). SHELLVAR is optional; if it is not supplied, the shell variable will be simply NAME. The purpose of this macro is to give the caller a way to access the name-mangling information other than through the C preprocessor as above; for example, to call Fortran routines from some language other than C/C++. automatically generated by info2www version 1.2.2.9 |