Customizing uncaught exception messages

Customizing uncaught exception messages

[Yang Zhang]

Hi, is it possible to get more informative error messages for uncaught 
exceptions?  For instance, I'm interested in getting Java-like 
tracebacks with file and line numbers.  Currently what I see is far from 
that, e.g.:

terminate called after throwing an instance of 'std::logic_error'
   what():  basic_string::_S_construct NULL not valid

Is there any way to hook into the exception handling mechanisms and 
produce such a traceback?  If the solution is platform-dependent, I am 
using GNU/Linux with gcc 4.2.3.

Thanks!
-- 
Yang Zhang
http://www.mit.edu/~y_z/

Re: Customizing uncaught exception messages

[me22]

On Thu, May 15, 2008 at 2:03 AM, Yang Zhang <yanghatespam@gmail.com> wrote:
> Hi, is it possible to get more informative error messages for uncaught
> exceptions?  For instance, I'm interested in getting Java-like tracebacks
> with file and line numbers.  Currently what I see is far from that, e.g.:
>
> terminate called after throwing an instance of 'std::logic_error'
>  what():  basic_string::_S_construct NULL not valid
>
> Is there any way to hook into the exception handling mechanisms and produce
> such a traceback?  If the solution is platform-dependent, I am using
> GNU/Linux with gcc 4.2.3.
>

The information isn't stored anywhere, so by the time you get an
exception falling out of main and calling terminate, it's no longer
available.

Your debugger might let you automatically break on throws...

Re: Customizing uncaught exception messages

[Joel Dice]

On Thu, 15 May 2008, Yang Zhang wrote:

> Hi, is it possible to get more informative error messages for uncaught 
> exceptions?  For instance, I'm interested in getting Java-like tracebacks 
> with file and line numbers.  Currently what I see is far from that, e.g.:
>
> terminate called after throwing an instance of 'std::logic_error'
>  what():  basic_string::_S_construct NULL not valid
>
> Is there any way to hook into the exception handling mechanisms and produce 
> such a traceback?  If the solution is platform-dependent, I am using 
> GNU/Linux with gcc 4.2.3.

In cases where the exception is thrown by your own code, you may be able 
to use backtrace() and backtrace_symbols(), declared in execinfo.h, to 
capture the stack trace before unwinding.  Then use addr2line (a command 
line utility included in binutils) to get the line numbers.

Re: Customizing uncaught exception messages

[Yang Zhang]

me22 wrote:
> On Thu, May 15, 2008 at 2:03 AM, Yang Zhang <yanghatespam@gmail.com> wrote:
>> Hi, is it possible to get more informative error messages for uncaught
>> exceptions?  For instance, I'm interested in getting Java-like tracebacks
>> with file and line numbers.  Currently what I see is far from that, e.g.:
>>
>> terminate called after throwing an instance of 'std::logic_error'
>>  what():  basic_string::_S_construct NULL not valid
>>
>> Is there any way to hook into the exception handling mechanisms and produce
>> such a traceback?  If the solution is platform-dependent, I am using
>> GNU/Linux with gcc 4.2.3.
>>
> 
> The information isn't stored anywhere, so by the time you get an
> exception falling out of main and calling terminate, it's no longer
> available.
> 
> Your debugger might let you automatically break on throws...

How does gdb manage to hook into the exception-throwing mechanisms to 
trigger breakpoints?  Would I be able to use the same approach to hook 
it up to code that simply stores the backtrace somewhere (perhaps 
thread-local storage), and then hook into the uncaught exception handler 
to print this stored backtrace?

-- 
Yang Zhang
http://www.mit.edu/~y_z/

Re: Customizing uncaught exception messages

[Yang Zhang]

Joel Dice wrote:
> On Thu, 15 May 2008, Yang Zhang wrote:
> 
>> Hi, is it possible to get more informative error messages for uncaught 
>> exceptions?  For instance, I'm interested in getting Java-like 
>> tracebacks with file and line numbers.  Currently what I see is far 
>> from that, e.g.:
>>
>> terminate called after throwing an instance of 'std::logic_error'
>>  what():  basic_string::_S_construct NULL not valid
>>
>> Is there any way to hook into the exception handling mechanisms and 
>> produce such a traceback?  If the solution is platform-dependent, I am 
>> using GNU/Linux with gcc 4.2.3.
> 
> In cases where the exception is thrown by your own code, you may be able 
> to use backtrace() and backtrace_symbols(), declared in execinfo.h, to 
> capture the stack trace before unwinding.  Then use addr2line (a command 
> line utility included in binutils) to get the line numbers.

I guess my question boils down to: how do I do the first thing you 
mentioned - that is, cause all throws to trigger my own code (which e.g. 
calls backtrace())?  I've used backtrace() and addr2line before, but I 
just don't know enough about how C++ exceptions work.

-- 
Yang Zhang
http://www.mit.edu/~y_z/

Re: Customizing uncaught exception messages

[Ian Lance Taylor]

Yang Zhang <yanghatespam@gmail.com> writes:

> I guess my question boils down to: how do I do the first thing you
> mentioned - that is, cause all throws to trigger my own code (which
> e.g. calls backtrace())?  I've used backtrace() and addr2line before,
> but I just don't know enough about how C++ exceptions work.

Use the standard set_terminate function to create your own terminate
handler.  It will be called for exceptions which aren't caught.

If you want to be called for exception which are caught, you need to
hook into __cxa_throw.

Ian