enable -Wformat-truncation with -Og (PR 79691)

enable -Wformat-truncation with -Og (PR 79691)

[Martin Sebor]

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Bug 79691 - -Wformat-truncation suppressed by (and only by) -Og
points out that the gimple-ssa-sprintf pass doesn't run when
this optimization option is used.  That's because I forgot to
add it to the set of optimization passes that run with that
option.  The attached trivial patch tested on x86_64 corrects
the oversight.

Is this okay for 7.0?

Martin

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PR tree-optimization/79691 - -Wformat-truncation suppressed by (and only by) -Og

gcc/ChangeLog:

	PR c/79691
	* passes.def (pass_all_optimizations_g): Enable pass_sprintf_length.

gcc/testsuite/ChangeLog:

	PR c/79691
	* gcc.dg/tree-ssa/pr79691.c: New test.

diff --git a/gcc/passes.def b/gcc/passes.def
index c09ec22..6b0f05b 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -364,6 +364,7 @@ along with GCC; see the file COPYING3.  If not see
       NEXT_PASS (pass_object_sizes);
       /* Fold remaining builtins.  */
       NEXT_PASS (pass_fold_builtins);
+      NEXT_PASS (pass_sprintf_length, true);
       /* Copy propagation also copy-propagates constants, this is necessary
          to forward object-size and builtin folding results properly.  */
       NEXT_PASS (pass_copy_prop);
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr79691.c b/gcc/testsuite/gcc.dg/tree-ssa/pr79691.c
new file mode 100644
index 0000000..badbfcd
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr79691.c
@@ -0,0 +1,27 @@
+/* PR tree-optimization/79691 - -Wformat-truncation suppressed by
+   (and only by) -Og
+
+   { dg-compile }
+   { dg-options "-Og -Wall" } */
+
+char d[2];
+
+/* Verify -Wformat-overflow works.  */
+void f (void)
+{
+  __builtin_sprintf (d, "%i", 123);   /* { dg-warning "directive writing 3 bytes" } */
+}
+
+/* Verify -Wformat-truncation works.  */
+void g (void)
+{
+  __builtin_snprintf (d, sizeof d, "%i", 1234);   /* { dg-warning "output truncated writing 4 bytes" } */
+}
+
+/* Verify -fprintf-return-value works.  */
+int h (void)
+{
+  return __builtin_snprintf (0, 0, "%i", 12345);
+}
+
+/* { dg-final { scan-tree-dump-not "snprintf" "optimized" } } */

Re: enable -Wformat-truncation with -Og (PR 79691)

[Richard Biener]

On Fri, Feb 24, 2017 at 1:35 AM, Martin Sebor <msebor@gmail.com> wrote:
> Bug 79691 - -Wformat-truncation suppressed by (and only by) -Og
> points out that the gimple-ssa-sprintf pass doesn't run when
> this optimization option is used.  That's because I forgot to
> add it to the set of optimization passes that run with that
> option.  The attached trivial patch tested on x86_64 corrects
> the oversight.
>
> Is this okay for 7.0?

Any reason for the placement before copy-prop?  I'd have done it
after pass_late_warn_uninitialized for example.

Also doesn't pass_sprintf_length rely on get_range_info ()?  With -Og
nothing populates those so you'll always get effectively VARYING ranges.

Richard.

> Martin

Re: enable -Wformat-truncation with -Og (PR 79691)

[Jakub Jelinek]

On Fri, Feb 24, 2017 at 11:10:51AM +0100, Richard Biener wrote:
> On Fri, Feb 24, 2017 at 1:35 AM, Martin Sebor <msebor@gmail.com> wrote:
> > Bug 79691 - -Wformat-truncation suppressed by (and only by) -Og
> > points out that the gimple-ssa-sprintf pass doesn't run when
> > this optimization option is used.  That's because I forgot to
> > add it to the set of optimization passes that run with that
> > option.  The attached trivial patch tested on x86_64 corrects
> > the oversight.
> >
> > Is this okay for 7.0?
> 
> Any reason for the placement before copy-prop?  I'd have done it
> after pass_late_warn_uninitialized for example.
> 
> Also doesn't pass_sprintf_length rely on get_range_info ()?  With -Og
> nothing populates those so you'll always get effectively VARYING ranges.

-O0 and -O1 are the same case with that though.

	Jakub

Re: enable -Wformat-truncation with -Og (PR 79691)

[Martin Sebor]

On 02/24/2017 03:10 AM, Richard Biener wrote:
> On Fri, Feb 24, 2017 at 1:35 AM, Martin Sebor <msebor@gmail.com> wrote:
>> Bug 79691 - -Wformat-truncation suppressed by (and only by) -Og
>> points out that the gimple-ssa-sprintf pass doesn't run when
>> this optimization option is used.  That's because I forgot to
>> add it to the set of optimization passes that run with that
>> option.  The attached trivial patch tested on x86_64 corrects
>> the oversight.
>>
>> Is this okay for 7.0?
>
> Any reason for the placement before copy-prop?  I'd have done it
> after pass_late_warn_uninitialized for example.

I wanted to make sure that folded sprintf return values would be
eligible for further copy propagation.  E.g., that a + b would
be folded into a constant:

   int foo (void)
   {
     int a = snprintf (0, 0, "%i", 123);
     int b = snprintf (0, 0, "%i", 1234);
     return a + b;
   }

But I could have easily missed some important use case where this
placement will compromise the warning.  I don't have any tests
for this one way or the other so I'm happy to go with your
recommendation.  Let me know which you think is more appropriate
(if you have a suggestion for a test case I'd be grateful).

>
> Also doesn't pass_sprintf_length rely on get_range_info ()?  With -Og
> nothing populates those so you'll always get effectively VARYING ranges.

It does when it's available but as Jakub noted, it works without
it as well (at -O0).

Thanks
Martin

Re: enable -Wformat-truncation with -Og (PR 79691)

[Richard Biener]

On Fri, Feb 24, 2017 at 6:51 PM, Martin Sebor <msebor@gmail.com> wrote:
> On 02/24/2017 03:10 AM, Richard Biener wrote:
>>
>> On Fri, Feb 24, 2017 at 1:35 AM, Martin Sebor <msebor@gmail.com> wrote:
>>>
>>> Bug 79691 - -Wformat-truncation suppressed by (and only by) -Og
>>> points out that the gimple-ssa-sprintf pass doesn't run when
>>> this optimization option is used.  That's because I forgot to
>>> add it to the set of optimization passes that run with that
>>> option.  The attached trivial patch tested on x86_64 corrects
>>> the oversight.
>>>
>>> Is this okay for 7.0?
>>
>>
>> Any reason for the placement before copy-prop?  I'd have done it
>> after pass_late_warn_uninitialized for example.
>
>
> I wanted to make sure that folded sprintf return values would be
> eligible for further copy propagation.  E.g., that a + b would
> be folded into a constant:
>
>   int foo (void)
>   {
>     int a = snprintf (0, 0, "%i", 123);
>     int b = snprintf (0, 0, "%i", 1234);
>     return a + b;
>   }
>
> But I could have easily missed some important use case where this
> placement will compromise the warning.  I don't have any tests
> for this one way or the other so I'm happy to go with your
> recommendation.  Let me know which you think is more appropriate
> (if you have a suggestion for a test case I'd be grateful).

Hmm, I see.  Note that I'd have expected this kind of constant folding
to happen in gimple-fold.c, but well.

>>
>> Also doesn't pass_sprintf_length rely on get_range_info ()?  With -Og
>> nothing populates those so you'll always get effectively VARYING ranges.
>
>
> It does when it's available but as Jakub noted, it works without
> it as well (at -O0).

Good.

Your original patch is ok.

Thanks,
Richard.

> Thanks
> Martin