(g77.info.gz) Other Compilers

 
 Other Compilers
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    An individual Fortran source file can be compiled to an object
 (`*.o') file instead of to the final program executable.  This allows
 several portions of a program to be compiled at different times and
 linked together whenever a new version of the program is needed.
 However, it introduces the issue of "object compatibility" across the
 various object files (and libraries, or `*.a' files) that are linked
 together to produce any particular executable file.
 
    Object compatibility is an issue when combining, in one program,
 Fortran code compiled by more than one compiler (or more than one
 configuration of a compiler).  If the compilers disagree on how to
 transform the names of procedures, there will normally be errors when
 linking such programs.  Worse, if the compilers agree on naming, but
 disagree on issues like how to pass parameters, return arguments, and
 lay out `COMMON' areas, the earliest detected errors might be the
 incorrect results produced by the program (and that assumes these
 errors are detected, which is not always the case).
 
    Normally, `g77' generates code that is object-compatible with code
 generated by a version of `f2c' configured (with, for example, `f2c.h'
 definitions) to be generally compatible with `g77' as built by `gcc'.
 (Normally, `f2c' will, by default, conform to the appropriate
 configuration, but it is possible that older or perhaps even newer
 versions of `f2c', or versions having certain configuration changes to
 `f2c' internals, will produce object files that are incompatible with
 `g77'.)
 
    For example, a Fortran string subroutine argument will become two
 arguments on the C side: a `char *' and an `int' length.
 
    Much of this compatibility results from the fact that `g77' uses the
 same run-time library, `libf2c', used by `f2c', though `g77' gives its
 version the name `libg2c' so as to avoid conflicts when linking,
 installing them in the same directories, and so on.
 
    Other compilers might or might not generate code that is
 object-compatible with `libg2c' and current `g77', and some might offer
 such compatibility only when explicitly selected via a command-line
 option to the compiler.
 
 work!*
(g77.info.gz) Other Compilers

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