FortranCInterface

This module provides variables and commands to detect Fortran/C Interface.

Load this module in a CMake project with:

include(FortranCInterface)

This module automatically detects the API by which C and Fortran languages interact.

Variables

Result Variables

Including this module defines the following variables that indicate if the mangling is found:

FortranCInterface_GLOBAL_FOUND

Boolean indicating whether global subroutines and functions are available.

FortranCInterface_MODULE_FOUND

Boolean indicating whether module subroutines and functions (declared by MODULE PROCEDURE) are available.

Input Variables

This module also provides the following variables to specify the detected mangling, though a typical use case does not need to reference them and can use the Commands below.

FortranCInterface_GLOBAL_PREFIX

Prefix for a global symbol without an underscore.

FortranCInterface_GLOBAL_SUFFIX

Suffix for a global symbol without an underscore.

FortranCInterface_GLOBAL_CASE

The case for a global symbol without an underscore, either UPPER or LOWER.

FortranCInterface_GLOBAL__PREFIX

Prefix for a global symbol with an underscore.

FortranCInterface_GLOBAL__SUFFIX

Suffix for a global symbol with an underscore.

FortranCInterface_GLOBAL__CASE

The case for a global symbol with an underscore, either UPPER or LOWER.

FortranCInterface_MODULE_PREFIX

Prefix for a module symbol without an underscore.

FortranCInterface_MODULE_MIDDLE

Middle of a module symbol without an underscore that appears between the name of the module and the name of the symbol.

FortranCInterface_MODULE_SUFFIX

Suffix for a module symbol without an underscore.

FortranCInterface_MODULE_CASE

The case for a module symbol without an underscore, either UPPER or LOWER.

FortranCInterface_MODULE_ORDER

Added in version 4.1.

Order of components for module symbols without an underscore:

MODULE_THEN_SYMBOL

The module name appears before the symbol name, i.e., <PREFIX><module><MIDDLE><symbol><SUFFIX>.

SYMBOL_THEN_MODULE

The module name appears after the symbol name, i.e., <PREFIX><symbol><MIDDLE><module><SUFFIX>.

FortranCInterface_MODULE__PREFIX

Prefix for a module symbol with an underscore.

FortranCInterface_MODULE__MIDDLE

Middle of a module symbol with an underscore that appears between the name of the module and the name of the symbol.

FortranCInterface_MODULE__SUFFIX

Suffix for a module symbol with an underscore.

FortranCInterface_MODULE__CASE

The case for a module symbol with an underscore, either UPPER or LOWER.

FortranCInterface_MODULE__ORDER

Added in version 4.1.

Order of components for module symbols with an underscore:

MODULE_THEN_SYMBOL

The module name appears before the symbol name, i.e., <PREFIX><module><MIDDLE><symbol><SUFFIX>.

SYMBOL_THEN_MODULE

The module name appears after the symbol name, i.e., <PREFIX><symbol><MIDDLE><module><SUFFIX>.

Variables For Additional Manglings

This module is aware of possible GLOBAL and MODULE manglings for many Fortran compilers, but it also provides an interface to specify new possible manglings. The following variables can be set before including this module to specify additional manglings:

FortranCInterface_GLOBAL_SYMBOLS

FortranCInterface_MODULE_SYMBOLS

before including this module to specify manglings of the symbols MySub, My_Sub, MyModule:MySub, and My_Module:My_Sub.

Commands

This module provides the following commands:

FortranCInterface_HEADER

Generates a C header file containing macros to mangle symbol names:

FortranCInterface_HEADER(
  <file>
  [MACRO_NAMESPACE <macro-ns>]
  [SYMBOL_NAMESPACE <ns>]
  [SYMBOLS [<module>:]<function> ...]
)

This command generates a <file> with definitions of the following macros:

#define FortranCInterface_GLOBAL (name,NAME) ...
#define FortranCInterface_GLOBAL_(name,NAME) ...
#define FortranCInterface_MODULE (mod,name, MOD,NAME) ...
#define FortranCInterface_MODULE_(mod,name, MOD,NAME) ...

These macros mangle four categories of Fortran symbols, respectively:

• Global symbols without '_': call mysub()
• Global symbols with '_' : call my_sub()
• Module symbols without '_': use mymod; call mysub()
• Module symbols with '_' : use mymod; call my_sub()

If mangling for a category is not known, its macro is left undefined. All macros require raw names in both lower case and upper case.

The options are:

MACRO_NAMESPACE

Replace the default FortranCInterface_ prefix with a given namespace <macro-ns>.

SYMBOL_NAMESPACE

Prefix all preprocessor definitions generated by the SYMBOLS option with a given namespace <ns>.

SYMBOLS

List symbols to mangle automatically with C preprocessor definitions:

<function>          ==> #define <ns><function> ...
<module>:<function> ==> #define <ns><module>_<function> ...

If the mangling for some symbol is not known then no preprocessor definition is created, and a warning is displayed.

FortranCInterface_VERIFY

Verifies that the Fortran and C/C++ compilers work together:

FortranCInterface_VERIFY([CXX] [QUIET])

This command tests whether a simple test executable using Fortran and C (and C++ when the CXX option is given) compiles and links successfully. The result is stored in the cache entry FortranCInterface_VERIFIED_C (or FortranCInterface_VERIFIED_CXX if CXX is given) as a boolean. If the check fails and QUIET is not given the command terminates with a fatal error message describing the problem. The purpose of this check is to stop a build early for incompatible compiler combinations. The test is built in the Release configuration.

Examples

Examples: Basic Usage

The following example creates a FC.h header that defines mangling macros FC_GLOBAL(), FC_GLOBAL_(), FC_MODULE(), and FC_MODULE_():

include(FortranCInterface)
FortranCInterface_HEADER(FC.h MACRO_NAMESPACE "FC_")

The next example creates a FCMangle.h header that defines the same FC_*() mangling macros as the previous example plus preprocessor symbols FC_mysub and FC_mymod_my_sub:

include(FortranCInterface)
FortranCInterface_HEADER(
  FCMangle.h
  MACRO_NAMESPACE "FC_"
  SYMBOL_NAMESPACE "FC_"
  SYMBOLS mysub mymod:my_sub
)

Example: Additional Manglings

The following example shows how to specify manglings of the symbols MySub, My_Sub, MyModule:MySub, and My_Module:My_Sub. The following code tells this module to try given GLOBAL and MODULE manglings. (The carets point at raw symbol names for clarity in this example but are not needed.)

set(FortranCInterface_GLOBAL_SYMBOLS mysub_ my_sub__ MYSUB_)
  #                                  ^^^^^  ^^^^^^   ^^^^^
set(FortranCInterface_MODULE_SYMBOLS
    __mymodule_MOD_mysub __my_module_MOD_my_sub)
  #   ^^^^^^^^     ^^^^^   ^^^^^^^^^     ^^^^^^

include(FortranCInterface)

# ...