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C++_CALLS_F77
C++ Main Program Calls FORTRAN77 Subroutines {#c_calls_f77-c-main-program-calls-fortran77-subroutines align="center"}

C++_CALLS_F77 is a directory of C++ programs which illustrates how a C++ main program can call a FORTRAN77 subroutine.

For this example, the KRONROD package is used. Note that the KRONROD library is available in C++ and in FORTRAN77, so this example is not created out of necessity (the C++ main program could have simply called the C++ version of KRONROD). Instead, it is intended as an example of how to do this when you have to (you don't have a C++ version of the routines you want to use.)

When calling a FORTRAN77 routine from a C++ function, there are some simple things that may be enough to guarantee success.

  • a FORTRAN77 subroutine is like a C++ void function, and should be declared this way in the C++ code. The qualifier extern should also be used.
  • a FORTRAN77 subroutine or function expects all its arguments to be passed by reference. This generally means simply that the C++ function must pass scalar variables by reference, not value.
  • typically, when the FORTRAN77 compiler compiles the FORTRAN77 code, the names of functions and subroutines are stored with an appended underscore. In order for these names to be found by the C++ code, it is necessary that the C++ code declare and invoke the FORTRAN functions and subroutines with the underscore explicitly appended to the name.
  • in many cases, a FORTRAN compiler is simply a "front end" to a corresponding C++ compiler, as in the case of the GNU compilers gfortran and g++, or the Intel compilers ifort and icpp. This means that, as long as the corresponding compilers are used to compile the FORTRAN77 and C++ codes, it is probably possible to use either compiler to link and load the object codes; however, the load command may need to specify explicitly certain libraries associated with one of the languages. For instance, if loading using the gcc command, it is necessary to include "-l gfortran" so that the FORTRAN I/O libraries, among others, are included in the build.

Licensing: {#licensing align="center"}

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages: {#languages align="center"}

C++_CALLS_F77 is available in a C version and a C++ version and a MATLAB version.

Related Data and Programs: {#related-data-and-programs align="center"}

C_CALLS_F77, C programs which illustrate a C program calling a FORTRAN77 subroutine.

C++_CALLS_C, C++ programs which call a C function.

C++_CALLS_F90, C++ programs which illustrate how a C++ main program can call a FORTRAN90 subroutine.

F77_CALLS_C++, FORTRAN77 programs which illustrate how a FORTRAN77 program can call a C++ function.

KRONROD, a C++ library which can compute a Gauss and Gauss-Kronrod pair of quadrature rules of arbitrary order, by Robert Piessens, Maria Branders.

KRONROD, a FORTRAN77 library which can compute a Gauss and Gauss-Kronrod pair of quadrature rules of arbitrary order, by Robert Piessens, Maria Branders.

MIXED C++ programs which call a function written in another programming language.

Reference: {#reference align="center"}

Source Code: {#source-code align="center"}

KRONROD is the FORTRAN77 source code for the KRONROD library. It should be essentially unchanged from the standard version.

KRONROD_PRB is the C++ source code for the main program. Some changes have been made from the standard version in order to adjust for the fact that we are calling a FORTRAN77 subroutine.

Examples and Tests: {#examples-and-tests align="center"}

You can go up one level to the C++ source codes.

Last revised on 07 December 2010.