From: "Vladimir Prus"

Subject: [boost] lexical_cast problem

Not again. :)

I've just updated my project to use boost 1.30 and also gcc 3.2 and see exception which reads:

bad lexical cast: source type value could not be interpreted as target, Target=i, Source=Ss

Ah, yes, good ol' g++ with its wonderfully descriptive type_info names... ;)

The simple reproduction recipe is:

#include #include <string>

int main() { boost::lexical_cast<int>(std::string(" 0")); }

Note the space in string. The exception does not occur with gcc 2.95, but only with 3.2. I wonder if this should/can be fixed? Personally, I'd expect

"Houston, we have a problem..." Hm, just now, I sent a reply to a similar problem report at Boost-Users list, about why whitespace skipping is turned off in the new lexical_cast version. It was to avoid having things like "lexical_caststd::string(' '); // Space character" work, which used to throw an exception. However, it seems this change has had undesired side-effects, in that code like the above now fails to work. Frankly, I don't know what to do with this... this

code to work.

And a related note: the exception's what() above is not quite helpfull.

The current version in the CVS has got a changed exception handling, where bad_lexical_cast now looks like this: class bad_lexical_cast : public std::bad_cast { public: // ... const std::type_info &source_type() const const std::type_info &target_type() const virtual const char *what() const throw() { return "bad lexical cast: " "source type value could not be interpreted as target"; } }; In other words, what() now returns the original text, and the type_info objects for the types used is now returned by member functions.

Is it possible to output the stringstream content (if source -> stringstream conversion was successfull?)

Yes, that's possible. I guess I'll leave it to Kevlin to comment on this. Thanks for the report, to both you and Tom Matelich at Boost-Users list. Regards, Terje