From: Eric Hodel <drbrain@...7.net>
Date: 2009-04-23T07:03:45+09:00
Subject: Re: rb_raise problem in C extension

On Apr 22, 2009, at 12:55, bdezonia@wisc.edu wrote:
> On Apr 22, 1:44 pm, Eric Hodel <drbr...@segment7.net> wrote:
>> On Apr 22, 2009, at 10:05, bdezo...@wisc.edu wrote:
>>> I am using Ruby 1.8.6-26 from the One Click Installer on Windows. I
>>> have a C extension that tries to calloc() memory. If the calloc()
>>> fails I call rb_raise(rb_eNoMemError,"Cannot allocate data"). My
>>> program is getting stuck in this code. Debugging (unfortunately via
>>> print statements) I can see that rb_raise() is going to be called.
>>> After that the exception is never caught by the outermost rescue  
>>> loop.
>>> The program just stops doing anything (0% cpu) except it keeps
>>> updating a timer in another thread. Are there things I need to know
>>> about rb_raise() and how to use it?
>>
>> If ruby is out of memory how could it allocate more memory to raise  
>> an
>> exception?
>>
>> Ruby itself allocates a NoMemError at startup to ensure it can raise
>> one when it runs out of memory.  You'll probably need to do the same.
>> See gc.c rb_memerror().
>
> There is plenty of memory available (4-6 gig free). But I'm asking
> calloc() for a 1 gb chunk and it can't find one. Is there a different
> exception I should throw in this case? Will the rb_raise() in my
> nested C code percolate out to my handler in my nested ruby code? (As
> a test for now I'm just changing it to an eException but would
> appreciate any feedback you have)

In that case, rb_raise should do what you want, however you may need  
to explicitly rescue it:

$ ruby
begin
   begin
     raise NoMemoryError
   rescue
     puts "caught with plain rescue"
   end
rescue Exception # or NoMemoryError
   puts "caught with rescue Exception"
end
^D
caught with rescue Exception


For this reason, you should use RuntimeError or StandardError  
(especially for custom error classes) instead of Exception, since  
Exception isn't caught by a plain rescue.