[m-rev.] for review: fix conditional breakpoints bug

[Ian MacLarty]

On 6 Feb 2006, at 03:13, Julien Fischer wrote:

>
> On Sun, 5 Feb 2006, Ian MacLarty wrote:
>
>> For review by anyone.
>>
>> Estimated hours taken: 3
>> Branches: main
>>
>> Fix a bug where subterm dependency tracking would break if a 
>> conditional
>> breakpoint was set.  When the condition of a conditional breakpoint is
>> evaluated, some Mercury code is called.  Conditional breakpoints were 
>> being
>> evaluated outside of the "safe" part of the call graph where the call
>> sequence number is saved and restored in case any traced Mercury code
>> updates the call sequence number.  This meant that the Mercury code 
>> used to
>> evaluate conditional breakpoints was updating the call sequence 
>> number and
>> confusing the declarative debugger.
>>
>> This type of error, where Mercury code is called and the original 
>> sequence
>> number is not restored afterwards has occured numerous times in the 
>> past
>> (for example it occured when Ralph introduced the list command), so I 
>> have
>> changed the MR_TRACE_CALL_MERCURY macro to save and restore the event,
>> sequence and depth numbers to prevent this kind of error in the 
>> future.
>> Previously the event, sequence and depth numbers were saved in an
>> MR_Event_Details structure at the start of MR_trace_event and 
>> restored at
>> the end.  The MR_Event_Details structure needed to be passed to all 
>> the
>> command functions in case there was a retry (since then the event, 
>> sequence
>> and depth numbers must not be restored to their original values, but 
>> to new
>> values).  This is now all unnecessary, since the event, sequence and 
>> depth
>> numbers will be restored after any Mercury code is called (as long as 
>> it is
>> wrapped in MR_TRACE_CALL_MERCURY).
>>
>> runtime/mercury_trace_base.h:
>> 	Save and restore the event, call sequence and depth numbers
>> 	when calling Mercury code.
>>
>> trace/mercury_trace.c:
>> trace/mercury_trace.h:
>> trace/mercury_trace_declarative.c:
>> trace/mercury_trace_declarative.h:
>> trace/mercury_trace_external.c:
>> trace/mercury_trace_internal.c:
>> trace/mercury_trace_spy.c:
>> trace/mercury_trace_util.c:
>> trace/mercury_trace_util.h:
>> 	Do not pass around event_details anymore.  And remove, now redundant,
>> 	saving and restoring of the event details before and after calling
>> 	Mercury code.
>>
>> tests/debugger/declarative/Mmakefile:
>> tests/debugger/declarative/condition_bug.inp:
>> tests/debugger/declarative/condition_bug.m:
>> 	Test that tracking of subterms works with conditional breakpoints.
>>
>
> ...
>
>> Index: trace/mercury_trace_spy.c
>> ===================================================================
>> RCS file: 
>> /home/mercury1/repository/mercury/trace/mercury_trace_spy.c,v
>> retrieving revision 1.25
>> diff -u -r1.25 mercury_trace_spy.c
>> --- trace/mercury_trace_spy.c	11 Jul 2005 07:30:31 -0000	1.25
>> +++ trace/mercury_trace_spy.c	4 Feb 2006 17:16:31 -0000
>> @@ -361,6 +361,12 @@
>>  const char  *MR_spy_point_cond_problem = NULL;
>>  MR_Spy_Cond *MR_spy_point_cond_bad = NULL;
>>
>> +/*
>> +** NOTE: MR_spy_cond_is_true may only be called from within 
>> MR_trace_event
>> +** (or one of its decendents), since it calls Mercury code to 
>> evaluate the
>
> s/decendents/descendents/
>

Actually I've removed that comment completely, since it's no longer 
true.  I added that comment before I decided to change 
MR_TRACE_CALL_MERCURY.

Ian.

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