Re: [RFA] Emit a warning for ineffective set VAR = EXP command

[Tristan Gingold <gingold@adacore.com>]

On May 9, 2012, at 3:53 PM, <Paul_Koning@Dell.com> <Paul_Koning@Dell.com> wrote:

> 
> On May 9, 2012, at 8:28 AM, Tristan Gingold wrote:
> 
>> 
>> On May 7, 2012, at 9:38 PM, Joel Brobecker wrote:
>> 
>>>>> This warns about "set variable $j++" presumably -- should the warning be 
>>>>> disabled for pre/post increments/decrements?
>>>> 
>>>> I am not opposed to disable warnings for pre/post inc/dec.
>>>> But this usage is dubious (the help explicitly mentions VAR=EXP !)
>>>> 
>>>> Opinion ?
>>> 
>>> I think we should avoid the warning for pre/post inc/dec. This
>>> type of expression might be a little outside the method proposed
>>> in our documentation, but I think it's still a perfectly valid
>>> expression that results in an assignment being performed.
>> 
>> I don't know who should approve this adjustment, but here is the version that deals with pre/post inc/dec.
>> Note that it still warns for expressions such as i++ * 2.
> 
> If you had it walk through the elts[] list, would it then work for that case?

Is it worth the burden ?

> 
> 	paul
> 
>> 
>> Tested on set-nowarns.exp.
>> 
>> Tristan.
>> 
>> 2012-05-09  Tristan Gingold  <gingold@adacore.com>
>> 
>> 	* printcmd.c (set_command): Add pre/post inc/dec.
>> 
>> diff --git a/gdb/printcmd.c b/gdb/printcmd.c
>> index 79e38f2..fa76296 100644
>> --- a/gdb/printcmd.c
>> +++ b/gdb/printcmd.c
>> @@ -1080,11 +1080,21 @@ set_command (char *exp, int from_tty)
>>  struct cleanup *old_chain =
>>    make_cleanup (free_current_contents, &expr);
>> 
>> -  if (expr->nelts >= 1
>> -      && expr->elts[0].opcode != BINOP_ASSIGN
>> -      && expr->elts[0].opcode != BINOP_ASSIGN_MODIFY
>> -      && expr->elts[0].opcode != BINOP_COMMA)
>> -    warning (_("Expression is not an assignment (and might have no effect)"));
>> +  if (expr->nelts >= 1)
>> +    switch (expr->elts[0].opcode)
>> +      {
>> +      case UNOP_PREINCREMENT:
>> +      case UNOP_POSTINCREMENT:
>> +      case UNOP_PREDECREMENT:
>> +      case UNOP_POSTDECREMENT:
>> +      case BINOP_ASSIGN:
>> +      case BINOP_ASSIGN_MODIFY:
>> +      case BINOP_COMMA:
>> +	break;
>> +      default:
>> +	warning
>> +	  (_("Expression is not an assignment (and might have no effect)"));
>> +      }
>> 
>>  evaluate_expression (expr);
>>  do_cleanups (old_chain);
>> 
>