diff mbox

C/C++ PATCH to implement -Wpointer-compare warning (PR c++/64767)

Message ID CADzB+2nx2urLeSBDzy7LZzRm+cw5QsR9JHC72dSwORtF17-usg@mail.gmail.com
State New
Headers show

Commit Message

Jason Merrill Sept. 21, 2016, 7:52 p.m. UTC 
On Mon, Sep 19, 2016 at 2:49 PM, Jason Merrill <jason@redhat.com> wrote:
> I suppose that an INTEGER_CST of character type is necessarily a
> character constant, so adding a check for !char_type_p ought to do the
> trick.

Indeed it does.  I'm checking this in:

Comments

Marek Polacek Sept. 23, 2016, 1:15 p.m. UTC | #1 
On Wed, Sep 21, 2016 at 03:52:09PM -0400, Jason Merrill wrote:
> On Mon, Sep 19, 2016 at 2:49 PM, Jason Merrill <jason@redhat.com> wrote:
> > I suppose that an INTEGER_CST of character type is necessarily a
> > character constant, so adding a check for !char_type_p ought to do the
> > trick.
> 
> Indeed it does.  I'm checking this in:

Nice, thanks.  What about the original patch?  We still need to warn
(or error for C++11) for pointer comparisons.

	Marek
Jason Merrill Sept. 23, 2016, 2:31 p.m. UTC | #2 
On Fri, Sep 23, 2016 at 9:15 AM, Marek Polacek <polacek@redhat.com> wrote:
> On Wed, Sep 21, 2016 at 03:52:09PM -0400, Jason Merrill wrote:
>> On Mon, Sep 19, 2016 at 2:49 PM, Jason Merrill <jason@redhat.com> wrote:
>> > I suppose that an INTEGER_CST of character type is necessarily a
>> > character constant, so adding a check for !char_type_p ought to do the
>> > trick.
>>
>> Indeed it does.  I'm checking this in:
>
> Nice, thanks.  What about the original patch?  We still need to warn
> (or error for C++11) for pointer comparisons.

If we still accept pointer comparisons in C++, that's another bug with
treating \0 as a null pointer constant.  This seems to be because
ocp_convert of \0 to int produces an INTEGER_CST indistinguishable
from literal 0.

Jason
diff mbox

Patch

commit d2f237ef0f63b3ee3da79bcbfad08fedb325d554
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Sep 21 10:58:39 2016 -0400

            Core 903
            * call.c (null_ptr_cst_p): Check char_type_p.

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 393aab9..2804bd8 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -527,6 +527,7 @@  null_ptr_cst_p (tree t)
     {
       /* Core issue 903 says only literal 0 is a null pointer constant.  */
       if (TREE_CODE (type) == INTEGER_TYPE
+	  && !char_type_p (type)
 	  && TREE_CODE (t) == INTEGER_CST
 	  && integer_zerop (t)
 	  && !TREE_OVERFLOW (t))
diff --git a/gcc/testsuite/g++.dg/cpp0x/nullptr36.C b/gcc/testsuite/g++.dg/cpp0x/nullptr36.C
new file mode 100644
index 0000000..5f43881
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/nullptr36.C
@@ -0,0 +1,3 @@ 
+// { dg-do compile { target c++11 } }
+
+void *p = '\0';			// { dg-error "invalid conversion" }