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Re: Safe to add a field to svn_error_t?

From: Stefan Fuhrmann <eqfox_at_web.de>
Date: Tue, 28 Dec 2010 14:29:20 +0100

On 24.12.2010 19:32, Blair Zajac wrote:
> On 12/24/10 6:07 AM, Hyrum K Wright wrote:
>> On Fri, Dec 24, 2010 at 12:10 AM, Blair Zajac<blair_at_orcaware.com>
>> wrote:
>>> The addition of "tracing" to svn_error_t in 1.7 currently uses a
>>> special
>>> message string "traced call". Instead of doing this, can we safely
>>> add an
>>> svn_boolean_t to svn_error_t the indicates if it is a traced error?
>>> While svn_error_t is public, I'm hoping most people are creating
>>> them with
>>> svn_error_create*(), so if that's the case, then code written and
>>> compiled
>>> against svn<= 1.6 would work fine when linked against a 1.7 library.
>>> Thoughts?
>> We don't explicitly say "only use approved methods to create this
>> object", but we are pretty implicit about it, with an entire
>> documentation group for "Error creation and destruction". I'm on the
>> fence on this, but would lean toward "go ahead and extend the struct"
>> if pressured.
>> What problem are you trying to solve?
> There's this comment in svn_error__is_tracing_link():
> svn_boolean_t
> svn_error__is_tracing_link(svn_error_t *err)
> {
> /* ### A strcmp()? Really? I think it's the best we can do unless
> ### we add a boolean field to svn_error_t that's set only for
> ### these "placeholder error chain" items. Not such a bad idea,
> ### really... */
> return (err && err->message && !strcmp(err->message, SVN_ERR__TRACED));
> #else
> return FALSE;
> #endif
> }

What is the use-case for this function anyways?

IMHO, an svn_error_t says "There was problem
$message when executing the instruction at $file,
$line. To be more precise it was <inner error info

The fact that most error messages are just "traced
call" simply means we did not bother to give more
specific descriptions. But I don't see a real semantic
difference because everybody along the calling
chain may have contributed to the problem.

At best one might use this function to reduce the
length of the error report hoping that all the default
text in between are not relevant to the particular
> I thought of two other solutions:
> 1) a sentinel message and we compare by address.
> 2) negative source file line numbers.
To me, they seems at least as "hacky" as the
current solution. I could easily live with them but
so can I with the current code.

-- Stefan^2.
Received on 2010-12-28 14:43:29 CET

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