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Re: [PATCH] Do not pass NULL for the string in catch_errors


On 10/22/2015 09:50 AM, Pedro Alves wrote:
On 10/22/2015 12:23 PM, Luis Machado wrote:
On 10/22/2015 09:07 AM, Pedro Alves wrote:
On 10/21/2015 12:14 PM, Luis Machado wrote:
On 09/10/2015 10:16 AM, Pedro Alves wrote:
On 09/09/2015 03:45 PM, Luis Machado wrote:
I caught a segmentation fault while running gdb.reverse/sigall-reverse.exp,
in a mingw32 GDB, in this code path. It boils down to the code trying to
strlen () a NULL pointer. I tracked things down and it looks like
record_full_message_wrapper_safe is the only occurrence.

We could also change catch_errors to check the char pointer and pass the
empty string automatically if the pointer is NULL. Then again, it seems like
catch_errors is going away at any time now, being potentially replaced
with catch_exceptions.

It's been marked superseded for years.  If you had fixed this by
converting this one instance, we'd be a little closer.  ;-)


Well, we shouldn't rush! :-)

Seriously, i've been looking into this and it doesn't look like
catch_exceptions/catch_exceptions_with_msg is something we'll want to
use in the long run either. Those couple functions also do not directly
replace catch_errors.

I thought about replacing the remaining catch_errors occurrences with
TRY/CATCH/END_CATCH blocks, which sounds better aligned with what we
want to do in the future - migrating to C++ etc. Then we can finally get
rid of catch_errors and a few useless wrappers. How does that sound?

Sounds like better leave it be then.  It may be that with proper C++/RAII
the try/catches would disappear altogether in the end, for instance.

I see. Unfortunately, for the cases where catch_exceptions supposedly
acts similarly to catch_errors, it still doesn't work correctly because
catch_exceptions doesn't seem to cope well with error () calls, like the
case inside record-full.c.

Now I'm confused -- why doesn't it?

But TBC, by "leave it be", I meant "just go with your original patch".

If you do want to go through and replace all catch_errors with
TRY/CATCH, I don't oppose it at all.  I guess I was just trying to
avoid imposing extra work on you.


That would be fine by me. I was just experimenting with TRY/CATCH/END_CATCH after my unsuccessful replacement of catch_errors with catch_exceptions. See below.

With catch_exceptions, instead of catching the error and letting the
inferior continue, it will just cause the inferior to terminate.

I don't understand.  Why do you say this will happen?


I replaced catch_errors with catch_exceptions in record-full.c. I saw a bunch of failures in gdb.reverse/sigall-reverse.exp, starting at this point:

Breakpoint 142, handle_TERM (sig=15) at ../../../gdb-head-ro/gdb/testsuite/gdb.reverse/sigall-reverse.c:378^M
378     }^M
(gdb) PASS: gdb.reverse/sigall-reverse.exp: send signal TERM
continue^M
Continuing.^M
The next instruction is syscall exit_group. It will make the program exit. Do you want to stop the program?([y] or n) yes^M
Process record: inferior program stopped.^M
^M
[process 21188] #1 stopped.^M

The above is a normal run. If i replace catch_errors with catch_exceptions, instead of stopping the inferior, it will terminate. Maybe there is a bug somewhere, or something is being mishandled.


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