[Bug c++/70172] incorrect reinterpret_cast from integer to pointer error on invalid constexpr initialization

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70172

Martin Sebor  changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 Resolution|--- |FIXED

--- Comment #6 from Martin Sebor  ---
Fixed by r234698.

[Bug c++/70172] incorrect reinterpret_cast from integer to pointer error on invalid constexpr initialization

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70172

--- Comment #5 from Martin Sebor  ---
Author: msebor
Date: Sat Apr  2 17:14:48 2016
New Revision: 234698

URL: https://gcc.gnu.org/viewcvs?rev=234698=gcc=rev
Log:
PR c++/67376 - [5/6 regression] Comparison with pointer to past-the-end
of array fails inside constant expression
PR c++/70170 - [6 regression] bogus not a constant expression error comparing
pointer to array to null
PR c++/70172 - incorrect reinterpret_cast from integer to pointer error
on invalid constexpr initialization
PR c++/70228 - insufficient detail in diagnostics for a constexpr out of bounds
array subscript

gcc/testsuite/ChangeLog:
2016-04-02  Martin Sebor  

PR c++/67376
PR c++/70170
PR c++/70172
PR c++/70228
* g++.dg/cpp0x/constexpr-array-ptr10.C: New test.
* g++.dg/cpp0x/constexpr-array-ptr9.C: New test.
* g++.dg/cpp0x/constexpr-nullptr-1.C: New test.
* g++.dg/cpp0x/constexpr-array5.C: Adjust text of expected diagnostic.
* g++.dg/cpp0x/constexpr-string.C: Same.
* g++.dg/cpp0x/constexpr-wstring2.C: Same.
* g++.dg/cpp0x/pr65398.C: Same.
* g++.dg/ext/constexpr-vla1.C: Same.
* g++.dg/ext/constexpr-vla2.C: Same.
* g++.dg/ext/constexpr-vla3.C: Same.
* g++.dg/ubsan/pr63956.C: Same.

gcc/cp/ChangeLog:
2016-04-02  Martin Sebor  

PR c++/67376
PR c++/70170
PR c++/70172
PR c++/70228
* constexpr.c (diag_array_subscript): New function.
(cxx_eval_array_reference): Detect out of bounds array indices.

gcc/ChangeLog:
2016-04-02  Martin Sebor  

PR c++/67376
* fold-const.c (maybe_nonzero_address): New function.
(fold_comparison): Call it.  Fold equality and relational
expressions involving null pointers.
(tree_single_nonzero_warnv_p): Call maybe_nonzero_address.

Added:
trunk/gcc/testsuite/g++.dg/cpp0x/constexpr-array-ptr10.C
trunk/gcc/testsuite/g++.dg/cpp0x/constexpr-array-ptr9.C
trunk/gcc/testsuite/g++.dg/cpp0x/constexpr-nullptr-1.C
Modified:
trunk/gcc/ChangeLog
trunk/gcc/cp/ChangeLog
trunk/gcc/cp/constexpr.c
trunk/gcc/fold-const.c
trunk/gcc/testsuite/ChangeLog
trunk/gcc/testsuite/g++.dg/cpp0x/constexpr-array5.C
trunk/gcc/testsuite/g++.dg/cpp0x/constexpr-string.C
trunk/gcc/testsuite/g++.dg/cpp0x/constexpr-wstring2.C
trunk/gcc/testsuite/g++.dg/cpp0x/pr65398.C
trunk/gcc/testsuite/g++.dg/ext/constexpr-vla1.C
trunk/gcc/testsuite/g++.dg/ext/constexpr-vla2.C
trunk/gcc/testsuite/g++.dg/ext/constexpr-vla3.C
trunk/gcc/testsuite/g++.dg/ubsan/pr63956.C

[Bug c++/70172] incorrect reinterpret_cast from integer to pointer error on invalid constexpr initialization

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70172

--- Comment #4 from Martin Sebor  ---
Patch posted for review:
https://gcc.gnu.org/ml/gcc-patches/2016-03/msg00796.html

[Bug c++/70172] incorrect reinterpret_cast from integer to pointer error on invalid constexpr initialization

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70172

Martin Sebor  changed:

   What|Removed |Added

 Status|UNCONFIRMED |ASSIGNED
   Last reconfirmed||2016-03-11
   Assignee|unassigned at gcc dot gnu.org  |msebor at gcc dot 
gnu.org
 Ever confirmed|0   |1

--- Comment #3 from Martin Sebor  ---
My patch for bug 67376 handles this case as well.

[Bug c++/70172] incorrect reinterpret_cast from integer to pointer error on invalid constexpr initialization

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70172

--- Comment #2 from Martin Sebor  ---
I should add that the bogus "reinterpret_cast" error goes away when the address
of a non-array member is used instead, as in the test case below, even though
this modified test case is also invalid for the same reason (using a null
pointer).  Failing to diagnose the modified test case is the subject of bug
60760.

$ cat z.c && /home/msebor/build/gcc-trunk-svn/gcc/xgcc
-B/home/msebor/build/gcc-trunk-svn/gcc -S -Wall -Wextra -Wpedantic -o/dev/null
-xc++ z.c
struct S { int a, b; } s;

constexpr S *p = (S*)0;
constexpr const int *q = >b;

[Bug c++/70172] incorrect reinterpret_cast from integer to pointer error on invalid constexpr initialization

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70172

Martin Sebor  changed:

   What|Removed |Added

   Keywords||diagnostic
 Blocks||55004
  Known to fail||6.0

--- Comment #1 from Martin Sebor  ---
I would normally make the Severity of a bug in the text of a diagnostic minor
but this one seems like it's more than a poorly phrased diagnostic.  The code
that triggers the error is in the potential_constant_expression_1() function in
constexp.c:

case NOP_EXPR:
case CONVERT_EXPR:
case VIEW_CONVERT_EXPR:
  /* -- a reinterpret_cast.  FIXME not implemented, and this rule
 may change to something more specific to type-punning (DR 1312).  */
  {
tree from = TREE_OPERAND (t, 0);
if (POINTER_TYPE_P (TREE_TYPE (t))
&& TREE_CODE (from) == INTEGER_CST
&& !integer_zerop (from))
  {
if (flags & tf_error)
  error_at (EXPR_LOC_OR_LOC (t, input_location),
"reinterpret_cast from integer to pointer");
return false;
  }
return (RECUR (from, TREE_CODE (t) != VIEW_CONVERT_EXPR));
  }


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55004
[Bug 55004] [meta-bug] constexpr issues