"yu jie" <yujie052@gmail.com> writes:

>> (let ((x -1))
>>   (while (condition-case nil
>> 	     (message "1.Expt is %e" (expt 10.0 x))
>> 	   (error nil))
>>     (message "1.`x' is now %d" (setq x (* 2 x))))
>>   (message "2.`x' is now %d" (setq x (/ x 2)))
>>   (while (condition-case nil
>> 	     (message "3.Expt is %e" (expt 10.0 x))
>> 	   (error nil))
>>     (message "3.`x' is now %d" (setq x (1- x))))
>>   (+ x 2))

> *Message*:
> 1.Expt is 1.000000e+000
> 1.`x' is now 0
> 1.Expt is 1.000000e+000
> 1.`x' is now 0
> 1.Expt is 1.000000e+000
> 1.`x' is now 0
> 1.Expt is 1.000000e+000
> Loading debug...done
> Entering debugger...

Thanks a lot.  As I read the pow(3) man page, the fact that it triggers
a ERANGE error is not documented, so it doesn't seem standard.

IMO, we should check by hand if an (under|over)flow is triggered.

Can you please try the following patch?