[Patch, Fortran] PR 22552: New warning -Wimplicit-procedure

[Daniel Kraft]

Hi,

this implements the warning asked for in PR 22552.  A new flag 
-Wimplicit-procedure is added, that warns about usage of a procedure 
never explicitly declared.  That is,

EXTERNAL :: foobar
CALL foobar ()

will not trigger this warning, as -Wimplicit-interface would do.  Also, 
something like

INTEGER :: foobar

also prevents the warning, as does an implicit type.  This means that 
the warning will only ever be issued for SUBROUTINES, as FUNCTIONS need 
to have a type.

See the test-case for a full example.

While I don't think this flag is very useful for new code (there 
-Wimplicit-interface could be used better, I guess, when only module 
procedures with explicit interfaces are used), the patch is quite 
straight-forward and thus I think we can include it to help with those 
codes not yet having only explicit-interface procedures.

I did build this patch on the code snipped provided by FX in the PR.

Regression-testing on GNU/Linux-x86-32 at the moment.  Do you think this 
new flag is ok, and ok for trunk if successful?

Yours,
Daniel

-- 
Done:  Arc-Bar-Cav-Ran-Rog-Sam-Tou-Val-Wiz
To go: Hea-Kni-Mon-Pri
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