Better behaviour for interactive apps on leaf overflow?

Hello! We’ve been using libgmp for our bignum support in XEmacs for a decade or so now, thanks to Jerry James, one of our more active developers. XEmacs Lisp is in spirit a Lisp-2 close in philosophy and history to Common Lisp, and it’s correct and pleasant to have good bignum support. One of our design (and implementation!) goals for XEmacs Lisp is that it should be impossible for Lisp to crash XEmacs, something very important in preserving our users’ data. We supply our own allocation functions to gmp and handle our failures ourselves to minimise the risk of that happening. But, it is still perfectly possible for Lisp to do something like this, where lsh is the bitwise left shift operation, and most-positive-fixnum is 2 to the 30th minus one: (lsh (lsh most-positive-fixnum #xFFFFFF80) #xFFFFFF80) On a 32-bit machine this will eventually fail with the following message: (gdb) r -batch -eval "(lsh (lsh most-positive-fixnum #xFFFFFF80) #xFFFFFF80)" Starting program: /Sources/xemacs-21.5-integer-length/src/xemacs -batch -eval "(lsh (lsh most-positive-fixnum #xFFFFFF80) #xFFFFFF80)" gmp: overflow in mpz type Program received signal SIGABRT, Aborted. 0x95187c5a in __kill () from /usr/lib/libSystem.B.dylib (gdb) Now, this abort isn’t wrapped, gmp calls it unconditionally in realloc.c:_mpz_realloc(). This is frustrating for XEmacs; from our perspective, we’d like to throw an error in this situation in the same way we do when we divide by zero, rather than crash the entire process and have the user lose so much of his or her state. Our garbage collector will take care of the lost memory. Best, Aidan Kehoe -- ‘Tramadol is further fed to cattle […] when working them […] (as draft animals) so that the animals do not get tired quickly. …’ — Angewandte Chemie, Sept 2014, describing the social context of (synthetic) tramadol having been found in Cameroon tree roots. _______________________________________________ XEmacs-Beta mailing list XEmacs-Beta(a)xemacs.org http://lists.xemacs.org/mailman/listinfo/xemacs-beta