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Subject: |
Re: 02-ac-lang-program-fortran-77.patch |
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Date: |
Tue, 07 Nov 2000 23:43:43 -0600 |
Akim Demaille wrote:
> from Akim Demaille <address@hidden>
> * aclang.m4 (AC_LANG_PROGRAM(Fortran 77): Complain about $1 having
> a value.
> (_AC_LANG_COMPILER_GNU): Pass the test as the body of
> AC_LANG_PROGRAM, not the prologue.
I am not sure what this ends up accomplishing. This change:
> -[_AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#ifndef __GNUC__
> +[_AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [[#ifndef __GNUC__
> choke me
> #endif
> ]])],
_still_ passes C code into the Fortran code (only this time it's between
the Fortran program statement and the end statement). When this macro
is
run for AC_LANG_PROGRAM(Fortran 77), it still puts C pre-processing
statements
into a `conftest.f' source file which is then compiled by F77!
$ cat conftest.f:
program main
#ifndef __GNUC__
choke me
#endif
end
$ g77 conftest.f
conftest.f:2: undefined or invalid # directive
conftest.f:3:
choke me
^
Non-numeric character at (^) in label field [info -f g77 M LEX]
conftest.f:4: undefined or invalid # directive
so it fails. Therefore, g77 is NOT a GNU compiler!
Now do this:
$ mv conftest.f conftest.F
$ g77 conftest.F
It works! It is a GNU compiler. Other compilers, like my SGI
and ABSOFT will fail on this. This is because g77, like other,
compilers use the file extension to determine if the C pre-processor
is to be run on the source before compiling.
>From 'info g77' section: Options Controlling the Kind of Output
> For any given input file, the file name suffix determines what kind
> of program is contained in the file--that is, the language in which the
> program is written is generally indicated by the suffix. Suffixes
> specific to GNU Fortran are listed below. *Note gcc: (Using and
> Porting GNU CC)Overall Options, for information on suffixes recognized
> by GNU CC.
>
> `FILE.f'
>
> `FILE.for'
>
> `FILE.FOR'
> Fortran source code that should not be preprocessed.
>
> Such source code cannot contain any preprocessor directives, such
> as `#include', `#define', `#if', and so on.
>
> You can force `.f' files to be preprocessed by `cpp' by using `-x
> f77-cpp-input'. *Note LEX::.
>
> `FILE.F'
>
> `FILE.fpp'
>
> `FILE.FPP'
> Fortran source code that must be preprocessed (by the C
> preprocessor `cpp', which is part of GNU CC).
>
> Note that preprocessing is not extended to the contents of files
> included by the `INCLUDE' directive--the `#include' preprocessor
> directive must be used instead.
I don't think this patch really accomplishes much. I reiterate that the
easiest and most effective fix is to replace the _AC_LANG_COMILER_GNU
macro with the AC_PROG_F77_GNU macro from autoconf 2.14.
Paul
--
I don't know Marge. Trying is the first step to failure.
-- Homer
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