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Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!minow
From: minow@decvax.UUCP (Martin Minow)
Newsgroups: net.lang
Subject: Runtime trapping of program bugs
Message-ID: <19@decvax.UUCP>
Date: Tue, 8-Jan-85 00:32:25 EST
Article-I.D.: decvax.19
Posted: Tue Jan  8 00:32:25 1985
Date-Received: Wed, 9-Jan-85 02:44:54 EST
References: <5143@rochester.UUCP>
Lines: 16

Ken Yap mentioned that the VMS Fortran compiler puts constants
in read-only memory so the operating system could trap subroutines
that incorrectly write to their parameters.  He asked if other
compilers did the same.

Some very old Fortran compilers initialized all variables to
an "illegal" floating point constant (I think -0 was used on
the 7090) to trap the fairly common error where a variable
was read before it was initialized.  The PDP-11 floating-point
format has an "illegal float" defined for just that purpose,
but I don't think it's used by any '11 language.

Martin Minow
decvax!minow