Hi Jeff,
it turned out, that the changed symmetric condition in the warning hit
at several places, but also caused two false positives which I had to
address first. I tried also building a recent glibc, which hit a false
positive when using __builtin_isinf_sign in boolean context, which
is used extensively by glibc. Furtunately there were zero new warnings
in linux, well done Linus ;)
glibc's math.h has this definition:
# if __GNUC_PREREQ (4,4) && !defined __SUPPORT_SNAN__
# define isinf(x) __builtin_isinf_sign (x)
and __builtin_isinf_sign(x) is internally folded as
isinf(x) ? (signbit(x) ? -1 : 1) : 0
which can trigger the warning if used in a boolean context.
We do not want to warn for if (isinf(x)) of course.
The other false positive was in dwarf2out, where we have this:
../../gcc-trunk/gcc/dwarf2out.c:26166:35: error: ?: using integer
constants in boolean context [-Werror=int-in-bool-context]
if (s->refcount
== ((DEBUG_STR_SECTION_FLAGS & SECTION_MERGE) ? 1 : 2))
~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
and:
#define DEBUG_STR_SECTION_FLAGS \
(HAVE_GAS_SHF_MERGE && flag_merge_debug_strings \
? SECTION_DEBUG | SECTION_MERGE | SECTION_STRINGS | 1 \
: SECTION_DEBUG)
which got folded in C++ to
if (s->refcount ==
((flag_merge_debug_strings ? SECTION_MERGE : 0) ? 1 : 2))
Because SECTION_MERGE = 0x08000, the condition for the warning is
satisfied here, but that is only an artifact that is created by the
folding of the outer COND_EXPR.
Additional to what you suggested, I relaxed the condition even more,
because I think it is also suspicious, if one of the branches is known
to be outside [0:1] and the other is unknown.
That caused another warning in the fortran FE, which was caused by
wrong placement of braces in gfc_simplify_repeat.
We have:
#define mpz_sgn(Z) ((Z)->size < 0 ? -1 : (Z)->size > 0)
Therefore the condition must be .. && mpz_sgn(X) != 0)
Previously that did not match, because -1 is outside [0:1]
but (Z)->size > 0 is unknown.
To suppress the bogus C++ warnings I had to suppress the warning
when the condition is fully folded in cp_convert_and_check and
c_common_truthvalue_conversion is called for the second time.
To suppress the bogus C warning on __builtin_isinf_sign I found
no other way than changing the expansion of that to
isinf(x) ? (signbit(x) ? -1 : 1) + 0 : 0
which is just enough to hide the inner COND_EXPR from
c_common_truthvalue_conversion, but gets immediately folded
away by fold_binary so it will cause no different code.
Furthermore the C++ test case df-warn-signedunsigned1.C also
triggered the warning, because here we have:
#define MAK (fl < 0 ? 1 : (fl ? -1 : 0))
And thus "if (MAK)" should be written as if (MAK != 0)
Finally, what I already wrote in my previous mail
the macros in gensupport.c mix binary and ternary
logic and should be cleaned up.
Bootstrap and reg-test with all languages on x86_64-pc-linux-gnu.
Is it OK for trunk?
Thanks
Bernd.
gcc:
2016-09-14 Bernd Edlinger <[email protected]>
PR c++/77434
* doc/invoke.texi: Document -Wcond-in-bool-context.
* gensupport.c (TRISTATE_AND, TRISTATE_OR,
TRISTATE_NOT): Fix a warning.
* tree.h (integer_zerop_or_onep): New helper function.
PR middle-end/77421
* dwarf2out.c (output_loc_operands): Fix an assertion.
c-family:
2016-09-14 Bernd Edlinger <[email protected]>
PR c++/77434
* c.opt (Wcond-in-bool-context): New warning.
* c-common.c (c_common_truthvalue_conversion): Warn on integer
constants in boolean context.
cp:
2016-09-14 Bernd Edlinger <[email protected]>
PR c++/77434
* cvt.c (cp_convert_and_check): Suppress Wint-in-bool-context here.
fortran:
2016-09-14 Bernd Edlinger <[email protected]>
PR c++/77434
* simplify.c (gfc_simplify_repeat): Fix a warning.
testsuite:
2016-09-14 Bernd Edlinger <[email protected]>
PR c++/77434
* c-c++-common/Wcond-in-bool-context.c: New test.
* g++.dg/delayedfold/df-warn-signedunsigned1.C: Fix a warning.
Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c (revision 240135)
+++ gcc/builtins.c (working copy)
@@ -7887,15 +7887,18 @@ fold_builtin_classify (location_t loc, tree fndecl
tree isinf_call = build_call_expr_loc (loc, isinf_fn, 1, arg);
signbit_call = fold_build2_loc (loc, NE_EXPR, integer_type_node,
- signbit_call, integer_zero_node);
+ signbit_call, integer_zero_node);
isinf_call = fold_build2_loc (loc, NE_EXPR, integer_type_node,
- isinf_call, integer_zero_node);
+ isinf_call, integer_zero_node);
- tmp = fold_build3_loc (loc, COND_EXPR, integer_type_node, signbit_call,
- integer_minus_one_node, integer_one_node);
tmp = fold_build3_loc (loc, COND_EXPR, integer_type_node,
- isinf_call, tmp,
- integer_zero_node);
+ signbit_call, integer_minus_one_node,
+ integer_one_node);
+ /* Avoid a possible -Wint-in-bool-context warning in C. */
+ tmp = fold_build2_loc (loc, PLUS_EXPR, integer_type_node, tmp,
+ integer_zero_node);
+ tmp = fold_build3_loc (loc, COND_EXPR, integer_type_node,
+ isinf_call, tmp, integer_zero_node);
}
return tmp;
Index: gcc/c-family/c-common.c
===================================================================
--- gcc/c-family/c-common.c (revision 240135)
+++ gcc/c-family/c-common.c (working copy)
@@ -4652,6 +4652,17 @@ c_common_truthvalue_conversion (location_t locatio
TREE_OPERAND (expr, 0));
case COND_EXPR:
+ if (warn_int_in_bool_context)
+ {
+ tree val1 = fold_for_warn (TREE_OPERAND (expr, 1));
+ tree val2 = fold_for_warn (TREE_OPERAND (expr, 2));
+ if ((TREE_CODE (val1) == INTEGER_CST
+ && !integer_zerop_or_onep (val1))
+ || (TREE_CODE (val2) == INTEGER_CST
+ && !integer_zerop_or_onep (val2)))
+ warning_at (EXPR_LOCATION (expr), OPT_Wint_in_bool_context,
+ "?: using integer constants in boolean context");
+ }
/* Distribute the conversion into the arms of a COND_EXPR. */
if (c_dialect_cxx ())
{
Index: gcc/c-family/c.opt
===================================================================
--- gcc/c-family/c.opt (revision 240135)
+++ gcc/c-family/c.opt (working copy)
@@ -545,6 +545,10 @@ Wint-conversion
C ObjC Var(warn_int_conversion) Init(1) Warning
Warn about incompatible integer to pointer and pointer to integer conversions.
+Wint-in-bool-context
+C ObjC C++ ObjC++ Var(warn_int_in_bool_context) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
+Warn for suspicious integer expressions in boolean context.
+
Wint-to-pointer-cast
C ObjC C++ ObjC++ Var(warn_int_to_pointer_cast) Init(1) Warning
Warn when there is a cast to a pointer from an integer of a different size.
Index: gcc/cp/cvt.c
===================================================================
--- gcc/cp/cvt.c (revision 240135)
+++ gcc/cp/cvt.c (working copy)
@@ -645,6 +645,7 @@ cp_convert_and_check (tree type, tree expr, tsubst
{
/* Avoid bogus -Wparentheses warnings. */
warning_sentinel w (warn_parentheses);
+ warning_sentinel c (warn_int_in_bool_context);
folded_result = cp_convert (type, folded, tf_none);
}
folded_result = fold_simple (folded_result);
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 240135)
+++ gcc/doc/invoke.texi (working copy)
@@ -273,7 +273,7 @@ Objective-C and Objective-C++ Dialects}.
-Wframe-larger-than=@var{len} -Wno-free-nonheap-object -Wjump-misses-init @gol
-Wignored-qualifiers -Wignored-attributes -Wincompatible-pointer-types @gol
-Wimplicit -Wimplicit-function-declaration -Wimplicit-int @gol
--Winit-self -Winline -Wno-int-conversion @gol
+-Winit-self -Winline -Wno-int-conversion -Wint-in-bool-context @gol
-Wno-int-to-pointer-cast -Winvalid-memory-model -Wno-invalid-offsetof @gol
-Winvalid-pch -Wlarger-than=@var{len} @gol
-Wlogical-op -Wlogical-not-parentheses -Wlong-long @gol
@@ -5837,6 +5837,14 @@ warning about it.
The restrictions on @code{offsetof} may be relaxed in a future version
of the C++ standard.
+@item -Wint-in-bool-context
+@opindex Wint-in-bool-context
+@opindex Wno-int-in-bool-context
+Warn for suspicious use of integer values where boolean values are expected,
+such as conditional expressions (?:) using non-boolean integer constants in
+boolean context, like @code{if (a <= b ? 2 : 3)}.
+This warning is enabled by @option{-Wall}.
+
@item -Wno-int-to-pointer-cast
@opindex Wno-int-to-pointer-cast
@opindex Wint-to-pointer-cast
Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c (revision 240135)
+++ gcc/dwarf2out.c (working copy)
@@ -2051,9 +2051,9 @@ output_loc_operands (dw_loc_descr_ref loc, int for
/* Make sure the offset has been computed and that we can encode it as
an operand. */
gcc_assert (die_offset > 0
- && die_offset <= (loc->dw_loc_opc == DW_OP_call2)
+ && die_offset <= (loc->dw_loc_opc == DW_OP_call2
? 0xffff
- : 0xffffffff);
+ : 0xffffffff));
dw2_asm_output_data ((loc->dw_loc_opc == DW_OP_call2) ? 2 : 4,
die_offset, NULL);
}
Index: gcc/fortran/simplify.c
===================================================================
--- gcc/fortran/simplify.c (revision 240135)
+++ gcc/fortran/simplify.c (working copy)
@@ -5127,7 +5127,7 @@ gfc_simplify_repeat (gfc_expr *e, gfc_expr *n)
if (len ||
(e->ts.u.cl->length &&
- mpz_sgn (e->ts.u.cl->length->value.integer)) != 0)
+ mpz_sgn (e->ts.u.cl->length->value.integer) != 0))
{
const char *res = gfc_extract_int (n, &ncop);
gcc_assert (res == NULL);
Index: gcc/gensupport.c
===================================================================
--- gcc/gensupport.c (revision 240135)
+++ gcc/gensupport.c (working copy)
@@ -201,15 +201,15 @@ add_implicit_parallel (rtvec vec)
#define TRISTATE_AND(a,b) \
((a) == I ? ((b) == N ? N : I) : \
(b) == I ? ((a) == N ? N : I) : \
- (a) && (b))
+ (a) == Y && (b) == Y ? Y : N)
#define TRISTATE_OR(a,b) \
((a) == I ? ((b) == Y ? Y : I) : \
(b) == I ? ((a) == Y ? Y : I) : \
- (a) || (b))
+ (a) == Y || (b) == Y ? Y : N)
#define TRISTATE_NOT(a) \
- ((a) == I ? I : !(a))
+ ((a) == I ? I : (a) == Y ? N : Y)
/* 0 means no warning about that code yet, 1 means warned. */
static char did_you_mean_codes[NUM_RTX_CODE];
Index: gcc/testsuite/c-c++-common/Wint-in-bool-context.c
===================================================================
--- gcc/testsuite/c-c++-common/Wint-in-bool-context.c (revision 0)
+++ gcc/testsuite/c-c++-common/Wint-in-bool-context.c (working copy)
@@ -0,0 +1,32 @@
+/* PR c++/77434 */
+/* { dg-options "-Wint-in-bool-context" } */
+/* { dg-do compile } */
+
+int foo (int a, int b)
+{
+ if (a > 0 && a <= (b == 1) ? 1 : 2) /* { dg-warning "boolean context" } */
+ return 1;
+
+ if (a > 0 && a <= (b == 2) ? 1 : 1) /* { dg-bogus "boolean context" } */
+ return 2;
+
+ if (a > 0 && a <= (b == 3) ? 0 : 2) /* { dg-warning "boolean context" } */
+ return 3;
+
+ if (a == (((b == 3) ? 1|2|4 : 1) & 2 ? 0 : 2)) /* { dg-bogus "boolean context" } */
+ return 4;
+
+ if (a <= b ? 1000-1 : 0 && (!a || !b)) /* { dg-warning "boolean context" } */
+ return 5;
+
+ if (a ? a : 1+1) /* { dg-warning "boolean context" } */
+ return 6;
+
+ if (a ? b : 0) /* { dg-bogus "boolean context" } */
+ return 7;
+
+ if (__builtin_isinf_sign ((float)a/b)) /* { dg-bogus "boolean context" } */
+ return 8;
+
+ return 0;
+}
Index: gcc/testsuite/g++.dg/delayedfold/df-warn-signedunsigned1.C
===================================================================
--- gcc/testsuite/g++.dg/delayedfold/df-warn-signedunsigned1.C (revision 240135)
+++ gcc/testsuite/g++.dg/delayedfold/df-warn-signedunsigned1.C (working copy)
@@ -7,7 +7,7 @@ extern int fl;
int foo (int sz)
{
- if (MAK) return 1;
+ if (MAK != 0) return 1;
return 0;
}
Index: gcc/tree.h
===================================================================
--- gcc/tree.h (revision 240135)
+++ gcc/tree.h (working copy)
@@ -4361,6 +4361,15 @@ extern int integer_nonzerop (const_tree);
extern int integer_truep (const_tree);
+/* integer_zerop_or_onep (tree x) is nonzero if X is an integer constant
+ of value 0 or 1. */
+
+static inline int
+integer_zerop_or_onep (const_tree x)
+{
+ return integer_zerop (x) || integer_onep (x);
+}
+
extern bool cst_and_fits_in_hwi (const_tree);
extern tree num_ending_zeros (const_tree);
