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C++ PATCH for core issue 703 (float narrowing/initializer-lists)
- From: Jason Merrill <jason at redhat dot com>
- To: gcc-patches List <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 20 Mar 2009 17:48:41 -0400
- Subject: C++ PATCH for core issue 703 (float narrowing/initializer-lists)
At the San Francisco meeting the core working group decided to loosen
the rules for narrowing conversion errors on floating point
constant-expressions: now we only complain if the value is outside the
range of the target type, we don't complain if it just loses precision.
Tested x86_64-pc-linux-gnu, applied to trunk.
2009-03-20 Jason Merrill <jason@redhat.com>
C++ core issue 703
* typeck2.c (check_narrowing): Don't complain about loss of
precision when converting a floating-point constant.
Index: cp/typeck2.c
===================================================================
*** cp/typeck2.c (revision 144978)
--- cp/typeck2.c (working copy)
*************** check_narrowing (tree type, tree init)
*** 677,694 ****
{
if (TYPE_PRECISION (type) < TYPE_PRECISION (ftype))
{
- ok = false;
if (TREE_CODE (init) == REAL_CST)
{
d = TREE_REAL_CST (init);
! if (exact_real_truncate (TYPE_MODE (type), &d)
! /* FIXME: As a temporary workaround for PR 36963, don't
! complain about narrowing from a floating
! literal. Hopefully this will be resolved at the
! September 2008 C++ meeting. */
! || !was_decl)
! ok = true;
}
}
}
else if (INTEGRAL_OR_ENUMERATION_TYPE_P (ftype)
--- 677,694 ----
{
if (TYPE_PRECISION (type) < TYPE_PRECISION (ftype))
{
if (TREE_CODE (init) == REAL_CST)
{
+ /* Issue 703: Loss of precision is OK as long as the value is
+ within the representable range of the new type. */
+ REAL_VALUE_TYPE r;
d = TREE_REAL_CST (init);
! real_convert (&r, TYPE_MODE (type), &d);
! if (real_isinf (&r))
! ok = false;
}
+ else
+ ok = false;
}
}
else if (INTEGRAL_OR_ENUMERATION_TYPE_P (ftype)
Index: testsuite/g++.dg/cpp0x/initlist5.C
===================================================================
*** testsuite/g++.dg/cpp0x/initlist5.C (revision 144923)
--- testsuite/g++.dg/cpp0x/initlist5.C (working copy)
*************** int k {}; // initialize to 0
*** 23,25 ****
--- 23,27 ----
// PR c++/39693
double d = 1.1;
float fa[] = { d, 1.1 }; // { dg-error "narrowing conversion of 'd'" }
+ const double d2 = 1.1;
+ float fa2[] = { d2, 1.1 };