Re: debugging guile test failure and segfault.

[Dan McMahill]

Ludovic Courtès wrote:
> Hi,
>
> Dan McMahill <address@hidden> writes:
>
> > a back trace showed that around line 834 of libguile/posix.c there is
> > a call to ttyname() which is returning NULL.   Unfortunately that NULL
> > pointer is used a few lines later by some functions which try to run
> > strlen() on it.  Thats where the segfault is.
>
> Good catch!  I committed a patch similar to yours along with a test case
> in CVS.
>
> > Running r4rs.test
> > ERROR: In procedure ttyname:
> > ERROR: No such file or directory
>
> I can't see what's causing this in `r4rs.test'.  Could you try running
> that test from the prompt and enter the debugger when the error is
> raised so that we get a Scheme stack trace?  Roughly:
>
>   $ ./pre-inst-guile
>   guile> (module-set! (resolve-module '(test-suite guile-test))
>                      'test-suite \"$PWD/test-suite/tests\")
>   guile> (module-set! (resolve-module '(test-suite guile-test))
>                       'tmp-dir "/tmp\)
>   guile> (load "test-suite/tests/r4rs.test")
>   [...]
>   ERROR: ...
>   guile> (debug)
>   debug> bt
>
> > Running regexp.test
> > Segmentation fault (core dumped)

# ./pre-inst-guile
guile> (module-set! (resolve-module '(test-suite guile-test))
'test-suite "$PWD/test-suite/tests")
guile> (module-set! (resolve-module '(test-suite guile-test)) 'tmp-dir
"/tmp")
guile> (load "test-suite/tests/r4rs.test")

[snip]
PASS: (6 9): (#<procedure list-length (obj)> (a b . c))
PASS: (6 9): (#<primitive-generic map> #<primitive-procedure cadr> ())

Backtrace:
In unknown file:
   ?: 0* [primitive-load "test-suite/tests/r4rs.test"]
In test-suite/tests/r4rs.test:
 923: 1*
Exception during displaying of backtrace: system-error

test-suite/tests/r4rs.test:88:45: In procedure ttyname in expression
(write (cons fun args) port):
test-suite/tests/r4rs.test:88:45: No such file or directory
ABORT: (system-error)
guile> (debug)
Frame 9 at test-suite/tests/r4rs.test:88:45
        ERROR: In procedure ttyname:
ERROR: No such file or directory
ABORT: (system-error)
guile>

this doesn't look promising.


> > #0  0x00000001600d6bb4 in scm_is_pair (x=0x10001202cbd60) at inline.h:272
> > #1  0x0000000160086434 in scm_sloppy_assq (key=0x1200673a0,
> > alist=0x10001202cbd60) at alist.c:53
> > #2  0x00000001600d2a58 in scm_hash_fn_get_handle (table=0x120321ac0,
> > obj=0x1200673a0, hash_fn=0x1600d15ec <scm_ihashq>,
> >     assoc_fn=0x160086408 <scm_sloppy_assq>, closure=0x0) at hashtab.c:428
> > #3  0x00000001600d2e20 in scm_hash_fn_ref (table=0x12009aba0,
> > obj=0x1200673a0, dflt=0x4, hash_fn=0x1600d15ec <scm_ihashq>,
> >     assoc_fn=0x160086408 <scm_sloppy_assq>, closure=0x0) at hashtab.c:500
> > #4  0x00000001600d3304 in scm_hashq_ref (table=0x12009aba0,
> > key=0x1200673a0, dflt=0x4) at hashtab.c:613
> > #5  0x00000001600dc904 in module_variable (module=0x12009ab40,
> > sym=0x1200673a0) at modules.c:289
> > #6  0x00000001600dcabc in scm_eval_closure_lookup (eclo=0x1200f56d0,
> > sym=0x1200673a0, definep=0x4) at modules.c:337
> > #7  0x00000001600dcf38 in scm_sym2var (sym=0x1200673a0,
> > proc=0x1200f56d0, definep=0x4) at modules.c:461
> > #8  0x00000001600a2d6c in scm_lookupcar1 (vloc=0x12071b1e0,
> > genv=0x120228620, check=1) at eval.c:2861
> > #9  0x00000001600a73b0 in ceval (x=0x12071b1e0, env=0x120228620) at
> > eval.c:4027
> > #10 0x00000001600a4d54 in ceval (x=0x1202286d0, env=0x120228620) at
> > eval.c:3557
> > #11 0x00000001600a3cb4 in ceval (x=0x12071adc0, env=0x12071aa10) at
> > eval.c:3384
> > #12 0x00000001600aa168 in scm_apply (proc=0x1201522c0, arg1=0x404,
> > args=0x12071aa30) at eval.c:4997
> > #13 0x00000001600a90b0 in scm_call_0 (proc=0x12071aaa0) at eval.c:4651
>
> This one is certainly trickier.  The stack trace above is that of a
> variable lookup (i.e., not related to regexps).  Can you try running
> `regexp.test' alone just to make sure?
>
> Address X is 8-byte aligned, which corresponds to a non-immediate.
> Could you try printing (from the debugger) `* ((SCM *) x)' and
> `* ((SCM *) x + 1)'?

now I'm having some problems reproducing this.  I'll keep trying.

-Dan