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Re: very obscure problem, help needed


From: Ian Grant
Subject: Re: very obscure problem, help needed
Date: Mon, 09 Oct 2000 10:14:08 +0100

>           ... are you by any chance doing anything with strings
> that you got back from Postgres?  I found that it is dangerous to
> treat such strings as shareable.  Specifically, I found that
> 
> (use-modules (database postgres))
> (use-modules (ice-9 string-fun))
> ...
> (sans-surrounding-whitespace (pg-getvalue dataset row col))
> 
> would cause mysterious errors later in the program.

This is the first time I've heard of such a problem.

> But if I use a private copy of sans-surrounding-whitespace, in which
> `make-shared-substring'

[now deprecated]

> is replaced by `substring', the program
> behaves correctly.

You should have reported this as a bug in guile or guile-pg.

I've checked the guile-pg code and I can't see a problem: the return value from 
pg_getvalue is a guile string created by either a call to scm_makfromstr 
(possibly via scm_makfrom0str).  This copies the string pointed to by the 
return value from the postgres client library into a freshly allocated (from 
scm_makstr) guile string.  Thereafter it should behave as any guile string does.

Does anybody know of any bugs with shared substrings in 1.4?

Ian
-- 
Ian Grant, Computer Lab., New Museums Site, Pembroke Street, Cambridge
Phone: +44 1223 334420          Personal e-mail: iang at pobox dot com 





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