What's the matter with "scm_string_p()"?

What's the matter with "scm_string_p()"?

[Bruce Korb]

Hi Guys,

In trying to "upgrade" things and expunge the "gh_" interface, I
tried to use "scm_string_p()" as a replacement for "gh_string_p()".
That lead to an extraordinarily obtuse seg fault that was only
solved by using gh_string_p(), despite its being deprecated.
(Both would appropriately return #t or #f, but it seems that
scm_string_p() modified some underlying thing that triggered the
seg fault.  The actual SCM value was 11124/0x2b74.)

Anybody with any guesses as to why?  In the end, I am finding I
need to AG_SCM_WHATEVER() macro-wrap my usage of the Guile interface
so that I can upgrade for each version.  1.6.x mostly avoids the
gh_* stuff -- except for gh_string_p.

Just in case you-all wanted to know.

Regards, Bruce


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Re: What's the matter with "scm_string_p()"?

[Kevin Ryde]

Bruce Korb <bkorb@gnu.org> writes:
>
> Anybody with any guesses as to why?

It'd have to be something pretty obscure, since gh_string_p is just

	return scm_is_true (scm_string_p (val))


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Re: What's the matter with "scm_string_p()"?

[Han-Wen Nienhuys]

Bruce Korb wrote:
> Hi Guys,
> 
> In trying to "upgrade" things and expunge the "gh_" interface, I
> tried to use "scm_string_p()" as a replacement for "gh_string_p()".
you're looking for scm_is_string()

-- 
  Han-Wen Nienhuys - hanwen@xs4all.nl - http://www.xs4all.nl/~hanwen



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Re: What's the matter?

[Bruce Korb]

On Monday 05 December 2005 02:27 pm, you wrote:
> Bruce Korb <bkorb@gnu.org> writes:
> >
> > In particular, using "scm_makstr(_s, _ch)" causes faults,
> 
> Looks like it ought to be ok.  Post a failing example to guile-devel
> if you like.

Hi Kevin,

It turns out that in all places where I was using scm_makstr(), I was
also using SCM_CHARS to access the string memory and then fill it in.
It *must* be safe to do because I don't call any scheme functions before
I am done scribbling in the memory.  Anyway, to be safer, I have removed
all use of SCM_CHARS and that made scm_makstr unusable so I am using a
new approach.  I do not use scm_makstr anymore.

Since it takes a *LOT* of work to get autogen-5.7.2 to run under
Guile 1.7.x, I don't think it worth the bother to try to use that
as an example.  If someone were to say, "I will work on the issue",
then I'll hack my autogen-5.8preXXX to use that function once again.
And fail.  Otherwise, lets forget it.

Thanks for your help.  Regards, Bruce

> Bruce Korb <bkorb@gnu.org> writes:
> >
> >     I should be getting stack traces on Scheme errors.  I'm not.
> >     (And, yes, I invoke either ``(backtrace)'' or ``scm_backtrace()''
> >     when a failure is detected.)
> 
> I think I've been having trouble with backtraces not appearing too
> (just from plain scheme code) but I didn't know where to look for
> what's wrong.

Me, either.  I did a bunch of grepping into the 1.4.1 and 1.6.7 source,
but nothing jumped out as the way it was accomplished.  Black magic?  :)
In the end, I've altered my test thus:

cat > ${testname}.samp6 <<EOF
${testname}.tpl6:7:4: In expression (stumble-over-unbound-variable):
${testname}.tpl6:7:4: Unbound variable: stumble-over-unbound-variable
Scheme evaluation error.  AutoGen ABEND-ing in template
	error.tpl6 on line 3
EOF

if test ${GUILE_VERSION} -gt 107000
then
  echo "WARNING:  Guile 1.7.x cannot display error line numbers" >&2
  exec 3> ${testname}.samp6-tmp
  echo 'ERROR: Unbound variable: stumble-over-unbound-variable' >&3
  sed 1,2d ${testname}.samp6 >&3
  exec 3>&-
  mv -f ${testname}.samp6-tmp ${testname}.samp6
fi


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Re: What's the matter?

[Marius Vollmer]

Bruce Korb <bkorb@gnu.org> writes:

> It turns out that in all places where I was using scm_makstr(), I
> was also using SCM_CHARS to access the string memory and then fill
> it in.  It *must* be safe to do because I don't call any scheme
> functions before I am done scribbling in the memory.

I would like to reproduce this.  Could you give me instructions for
how to do that?

What you describe _ought_ to work.  If we can't get SCM_CHARS /
SCM_STRING_CHARS to work we might as well remove it.

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