Re: [Boost-users] [xpressive] crash again :(

From: Eric Niebler (eric_at_[hidden])
Date: 2007-10-18 17:27:42

Eric Niebler wrote:
> Eric Niebler wrote:
>> Ovanes Markarian wrote:
>>> Hello Eric,
>>>
>>> sorry for bothering. I use xpressive in the following context:
>> <snip>
>>
>> I can't get your code to compile. Please send a minimal and complete 
>> source file that demonstrates the problem.
> 
> After fiddling with your code a bit, I got it to compile, but I'm not 
> seeing any assertions, exceptions or crashes. What version are you using?

Me again. I realized I wasn't seeing the problem because I hadn't put 
any strings in the vector over which you were iterating. When I do, I 
can reproduce the assert. This is not a bug in xpressive, it is a bug in 
your code. The problem is here:

std::tr1::bind(&apply_regex, sem_separated, td::tr1::placeholders::_1)

In this call to bind, you pass sem_separated to bind() *by value*. You 
return a regex_token_iterator, which holds a reference to the 
(temporary) regex object. When the temporary regex object goes away, the 
regex_token_iterators are left holding dangling references.

The lifetime of a regex_token_iterator cannot exceed the lifetime of the 
regex it holds.

If you change the code to ...

std::tr1::bind(&apply_regex, std::tr1::ref(sem_separated), 
td::tr1::placeholders::_1)

... it works just fine.

HTH,

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com