🚀 go-pugleaf

In article <1611@imec.UUCP> donne@imec.be (Werner Donne) wrote:
> Why is the assignment illegal?
In article <1992Apr15.014523.5364@cs.mcgill.ca>,
storm@cs.mcgill.ca (Marc WANDSCHNEIDER) replied:
> As far as I can see, it isn't.  I ran it on cc for the NeXTs, gcc
> running under SunOS 4.1.1 and as well, on MSC and Borland C++ 3.0 on my
> PC in front of me...  Not one compiler even complained about the assignment.

Encore Multimax running their version of 4.3BSD:
% cat foo.c
int main(void) { const char **a; char **b; a = b; return 0; }
% gcc -ansi -pedantic foo.c
foo.c: In function main:
foo.c:1: warning: assignment between incompatible pointer types

Quite right too.  The handling of read/write modifiers on pointers
was pretty well worked out in Mark Rain's "MARY" language, so there
was relevant (MARY was an Algol-68-derivative for systems programming)
prior art.
-- 
I am writing a book on debugging aimed at 1st & 2nd year CS students using
C/Modula/Pascal-like languages.  Please send suggestions (other than "you
_must_ cite "C Traps and Pitfalls") to ok@goanna.cs.rmit.oz.au