[RFC, PATCH] Display inlining context for uninitialized warnings

Jeff Law law@redhat.com
Wed Jun 19 16:13:00 GMT 2019

On 6/19/19 8:57 AM, Martin Sebor wrote:
> On 6/19/19 5:11 AM, Vladislav Ivanishin wrote:
>> Hi,
>> This patch (partially) adds displaying inlining context for
>> -W{maybe,}uninitialized warnings.  This is not as trivial to enable as
>> simply supplying the "%G" format specifier, so I have some questions
>> below.
>> I need this hunk
>>   void
>>   percent_K_format (text_info *text, location_t loc, tree block)
>>   {
>> -  text->set_location (0, loc, SHOW_RANGE_WITH_CARET);
>> +  if (loc != UNKNOWN_LOCATION)
>> +    text->set_location (0, loc, SHOW_RANGE_WITH_CARET);
>>    for two reasons:
>> - The gimple return stmt has UNKNOWN_LOCATION due to this code in
>>    lower_gimple_return ():
>>    if (gimple_return_retval (stmt) == gimple_return_retval (tmp_rs.stmt))
>>      {
>>        /* Remove the line number from the representative return
>> statement.
>>           It now fills in for many such returns.  Failure to remove this
>>           will result in incorrect results for coverage analysis.  */
>>        gimple_set_location (tmp_rs.stmt, UNKNOWN_LOCATION);
> This code is also causing quite a few non-trivial instances of
> -Wreturn-local-addr to have no location after two (or more) such
> statements have been merged (I raised PR 90735 for it), independent
> of inlining.  I wonder if using the location of the closing curly
> brace of the function definition (if it's available somewhere)
> would work without messing up the coverage analysis.
>>    (In case you are wondering, the code and the comment were
>>    added in 2004.)
>> - When percent_K_format is called, TEXT might already hold precise
>>    location information in case its (indirect) caller is
>>    warning_at/error_at.  So it seems to me, this function lacks
>>    distinguishing the two cases: being called from plain warning/error
>>    functions vs. their *_at counterparts (the location shouldn't be
>>    updated in the latter case).
>>    Martin, you did the necessary work for percent_G_format to accept
>>    arbitrary gimple statements rather than just calls for PR86650, but
>>    left the PR open.  Do you remember running into that sort of problem,
>>    or was it something else?
> I'm not sure it was the same problem.  I described what I was seeing
> when I posted the patch:
> https://gcc.gnu.org/ml/gcc-patches/2018-07/msg01286.html
> I think it's worth revisiting this with your patch in place.  It would
> be nice to get the inlining context in place for -Warray-bounds too.
> David Malcolm (CC'd) is the expert on locations and the diagnostic
> subsystem so he will have a much better insight than me into all of
> this than me.
You might also want to bring in Andreas K who added the original bits to
help with debug info generation and Eric B who extended that code in
2014 due to impacts on profiling.



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