Re: Discussion about why GNU/Linux system upgrades cause old programs to break

Richard Stallman <[email protected]> writes:

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> [[[ whether defending the US Constitution against all enemies,     ]]]
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>
>   > > So I wonder, why was the result failure rather than such warnings.
>   > > Eli, would you like to investigate why?
>   > >
>   > >       ~$ gcc -x c -std=gnu89 - <<<'main(argc, argv) int argc; char **argv; {
>   > > char *x = reallocarray(strdup (argv[0]), 100, 1); printf ("%d %s\n", argc, x);
>   > > exit (0); }'
>   > >
>   > > What is the problem with this one?  Is it that the value of strdup is 64 bits
>   > > and reallocarray's first argument is taken as int?
>
>   > Yes, the implicit declaration that K&R C specifies for undeclared
>   > functions can easily mismatch what the actual definition is, and indeed
>   > it is incorrect for reallocarray, so it breaks.
>
> Similar code (in Emacs 23 ?) worked in the past -- this problem did not
> occur, it seems.  Why did that code work then?

Maybe it ran on a 32-bit machine, where pointers and ints are both
32-bit values.

Maybe the user got lucky, and 'malloc' never returned a pointer greater
than or equal to 2<<32, so that truncating it had no effect.

Or, maybe Emacs included <string.h> and thus had the correct prototypes
for the above functions available.
-- 
Arsen Arsenović

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