Re: repost: segfault on GNU/Linux

[Richard Stallman]

    Program received signal SIGSEGV, Segmentation fault.
    0x08203e7c in find_interval (tree=3D0x9fc13cc, position=3D1) at intervals.c=
    :652
    652         tree =3D balance_possible_root_interval (tree);
    (gdb) l

That pretty clearly suggests that the interval structure (text
properties) contains invalid data.  That is very strange, since the
previous but seems to concern overlays.  Overlays and text properties are
different data and are handled by different code.

Can you come up with a single reproducible case that always fails
in the same way?

    Fails only with CVS Emacs, Emacs 21.3 works.

This means we can't expect the bug to disappear automatically
with the next release.

                                                 XEmacs can't be tested,

Even if it could be tested, the results would not teach us anything
about this bug.  XEmacs does not have either intervals or overlays.

All my experience suggests that the approach of trying various cases
to look for a pattern of where failures occur is not useful, because
it generally does not lead anywhere.

The only way to find such bugs is by studying the code in detail,
finding what's invalid in the data, and tracing the causality back
step by step.