modifying constants in Fortran and elsewhere

From	gah4 <gah4@u.washington.edu>
Newsgroups	comp.compilers
Subject	modifying constants in Fortran and elsewhere
Date	2023-07-10 19:42 -0700
Organization	Compilers Central
Message-ID	<23-07-003@comp.compilers> (permalink)

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A potential bug since the earliest days of Fortran is passing a
constant to a subroutine, and then changing the value of the dummy
argument.

In at least some Fortran system, this modifies the value of a constant
used other places in a program.

As this was known when PL/I was designed, it is defined such that
modifiable constants are passed to called procedures. C avoids it by
not allowing the & operator on constants. (Though K&R allows
modification of string constants.)

Somehow, in all the years, that feature was never added to Fortran.

It is easy to write programs and test for it, but I wonder if there
are any stories for real program that had this bug, and even better,
stories about the difficulty of finding it, or problems caused by it.

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modifying constants in Fortran and elsewhere gah4 <gah4@u.washington.edu> - 2023-07-10 19:42 -0700
  Re: modifying constants in Fortran and elsewhere Thomas Koenig <tkoenig@netcologne.de> - 2023-07-15 10:57 +0000
    Re: modifying constants in Fortran and elsewhere Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2023-07-16 11:56 +0200
    Re: modifying constants in Fortran and elsewhere Thomas Koenig <tkoenig@netcologne.de> - 2023-07-16 13:08 +0000
      Re: modifying constants in Fortran and elsewhere gah4 <gah4@u.washington.edu> - 2023-07-16 19:09 -0700
        Re: modifying constants in Fortran and elsewhere gah4 <gah4@u.washington.edu> - 2023-07-17 10:51 -0700
      Re: modifying constants in Fortran and elsewhere gah4 <gah4@u.washington.edu> - 2023-07-16 19:17 -0700
  Re: modifying constants in Fortran and elsewhere David Brown <david.brown@hesbynett.no> - 2023-07-17 13:09 +0200

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