Hi,
as far as I can see this 4.9/5 regression, where we spuriously warn
about the left shifts in the templates, has to do with r208183, where
Jason replaced c_inhibit_evaluation_warnings fiddling in
tsubst_copy_and_build with two warning_sentinels, on warn_type_limits
and warn_div_by_zero. In the present testcase, the triggering warning is
the one about left shift count >= width of type, which currently doesn't
have a name. Thus I think we can easily solve the issue by giving the
warning a name (likewise for the negative count warning) and using again
warning_sentinel. The names I picked are the same already used by clang.
Tested x86_64-linux. In case, what about 4.9?
Thanks,
Paolo.
//////////////////////////
2014-11-10 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/63265
* c-family/c.opt ([Wshift-count-negative, Wshift-count-overflow]): Add.
* doc/invoke.texi: Document the latter.
/cp
2014-11-10 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/63265
* pt.c (tsubst_copy_and_build, case LSHIFT_EXPR): Use warning_sentinels
on warn_shift_count_negative and warn_shift_count_overflow.
* typeck.c (cp_build_binary_op): Use OPT_Wshift_count_negative and
OPT_Wshift_count_overflow in the warnings.
/c
2014-11-10 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/63265
* c-typeck.c (build_binary_op): Use OPT_Wshift_count_negative and
OPT_Wshift_count_overflow in the warnings.
/testsuite
2014-11-10 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/63265
* g++.dg/cpp0x/constexpr-63265.C: New.
Index: c/c-typeck.c
===================================================================
--- c/c-typeck.c (revision 217282)
+++ c/c-typeck.c (working copy)
@@ -10545,7 +10545,8 @@ build_binary_op (location_t location, enum tree_co
{
int_const = false;
if (c_inhibit_evaluation_warnings == 0)
- warning_at (location, 0, "left shift count is negative");
+ warning_at (location, OPT_Wshift_count_negative,
+ "left shift count is negative");
}
else if (compare_tree_int (op1, TYPE_PRECISION (type0)) >= 0)
@@ -10552,8 +10553,8 @@ build_binary_op (location_t location, enum tree_co
{
int_const = false;
if (c_inhibit_evaluation_warnings == 0)
- warning_at (location, 0, "left shift count >= width of "
- "type");
+ warning_at (location, OPT_Wshift_count_overflow,
+ "left shift count >= width of type");
}
}
Index: c-family/c.opt
===================================================================
--- c-family/c.opt (revision 217282)
+++ c-family/c.opt (working copy)
@@ -760,14 +760,22 @@ Wselector
ObjC ObjC++ Var(warn_selector) Warning
Warn if a selector has multiple methods
+Wsequence-point
+C ObjC C++ ObjC++ Var(warn_sequence_point) Warning LangEnabledBy(C ObjC C++
ObjC++,Wall)
+Warn about possible violations of sequence point rules
+
Wshadow-ivar
ObjC ObjC++ Var(warn_shadow_ivar) EnabledBy(Wshadow) Init(1) Warning
Warn if a local declaration hides an instance variable
-Wsequence-point
-C ObjC C++ ObjC++ Var(warn_sequence_point) Warning LangEnabledBy(C ObjC C++
ObjC++,Wall)
-Warn about possible violations of sequence point rules
+Wshift-count-negative
+C ObjC C++ ObjC++ Var(warn_shift_count_negative) Init(1) Warning
+Warn if left shift count is negative
+Wshift-count-overflow
+C ObjC C++ ObjC++ Var(warn_shift_count_overflow) Init(1) Warning
+Warn if left shift count >= width of type
+
Wsign-compare
C ObjC C++ ObjC++ Var(warn_sign_compare) Warning LangEnabledBy(C++ ObjC++,Wall)
Warn about signed-unsigned comparisons
Index: cp/pt.c
===================================================================
--- cp/pt.c (revision 217282)
+++ cp/pt.c (working copy)
@@ -14680,6 +14680,8 @@ tsubst_copy_and_build (tree t,
{
warning_sentinel s1(warn_type_limits);
warning_sentinel s2(warn_div_by_zero);
+ warning_sentinel s3(warn_shift_count_negative);
+ warning_sentinel s4(warn_shift_count_overflow);
tree op0 = RECUR (TREE_OPERAND (t, 0));
tree op1 = RECUR (TREE_OPERAND (t, 1));
tree r = build_x_binary_op
Index: cp/typeck.c
===================================================================
--- cp/typeck.c (revision 217282)
+++ cp/typeck.c (working copy)
@@ -4328,7 +4328,8 @@ cp_build_binary_op (location_t location,
{
if ((complain & tf_warning)
&& c_inhibit_evaluation_warnings == 0)
- warning (0, "left shift count is negative");
+ warning (OPT_Wshift_count_negative,
+ "left shift count is negative");
}
else if (compare_tree_int (const_op1,
TYPE_PRECISION (type0)) >= 0)
@@ -4335,7 +4336,8 @@ cp_build_binary_op (location_t location,
{
if ((complain & tf_warning)
&& c_inhibit_evaluation_warnings == 0)
- warning (0, "left shift count >= width of type");
+ warning (OPT_Wshift_count_overflow,
+ "left shift count >= width of type");
}
}
/* Convert the shift-count to an integer, regardless of
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi (revision 217282)
+++ doc/invoke.texi (working copy)
@@ -269,6 +269,7 @@ Objective-C and Objective-C++ Dialects}.
-Wpointer-arith -Wno-pointer-to-int-cast @gol
-Wredundant-decls -Wno-return-local-addr @gol
-Wreturn-type -Wsequence-point -Wshadow -Wno-shadow-ivar @gol
+-Wshift-count-negative -Wshift-count-overflow @gol
-Wsign-compare -Wsign-conversion -Wfloat-conversion @gol
-Wsizeof-pointer-memaccess -Wsizeof-array-argument @gol
-Wstack-protector -Wstack-usage=@var{len} -Wstrict-aliasing @gol
@@ -3825,6 +3826,16 @@ exceptions are @samp{main} and functions defined i
This warning is enabled by @option{-Wall}.
+@item -Wshift-count-negative
+@opindex Wshift-count-negative
+@opindex Wno-shift-count-negative
+Warn if left shift count is negative. This warning is enabled by default.
+
+@item -Wshift-count-overflow
+@opindex Wshift-count-overflow
+@opindex Wno-shift-count-overflow
+Warn if left shift count >= width of type. This warning is enabled by default.
+
@item -Wswitch
@opindex Wswitch
@opindex Wno-switch
Index: testsuite/g++.dg/cpp0x/constexpr-63265.C
===================================================================
--- testsuite/g++.dg/cpp0x/constexpr-63265.C (revision 0)
+++ testsuite/g++.dg/cpp0x/constexpr-63265.C (working copy)
@@ -0,0 +1,19 @@
+// PR c++/63265
+// { dg-do compile { target c++11 } }
+
+#define LSHIFT (sizeof(unsigned int) * __CHAR_BIT__)
+
+template <int lshift>
+struct SpuriouslyWarns1 {
+ static constexpr unsigned int v = lshift < LSHIFT ? 1U << lshift : 0;
+};
+
+static_assert(SpuriouslyWarns1<LSHIFT>::v == 0, "Impossible occurred");
+
+template <int lshift>
+struct SpuriouslyWarns2 {
+ static constexpr bool okay = lshift < LSHIFT;
+ static constexpr unsigned int v = okay ? 1U << lshift : 0;
+};
+
+static_assert(SpuriouslyWarns2<LSHIFT>::v == 0, "Impossible occurred");
