re PR c/77490 (bit-not (~) on boolean should be warned about)

PR c/77490 * c.opt (Wbool-operation): New. * c-typeck.c (build_unary_op): Warn about bit not on expressions that have boolean value. Warn about ++/-- on booleans. * typeck.c (cp_build_unary_op): Warn about bit not on expressions that have boolean value. * doc/invoke.texi: Document -Wbool-operation. * c-c++-common/Wbool-operation-1.c: New test. * gcc.dg/Wbool-operation-1.c: New test. From-SVN: r240462
2016-09-24 09:39:23 +00:00 · 2016-09-24 09:39:23 +00:00 · 9a2300e956
parent 02ae505bc9
commit 9a2300e956
11 changed files with 134 additions and 4 deletions
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@ -1,3 +1,8 @@
+2016-09-24  Marek Polacek  <polacek@redhat.com>
+
+	PR c/77490
+	* doc/invoke.texi: Document -Wbool-operation.
+
 2016-09-23  Jakub Jelinek  <jakub@redhat.com>

 	* hooks.c (hook_bool_bool_false, hook_bool_bool_gcc_optionsp_false,
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@ -1,3 +1,8 @@
+2016-09-24  Marek Polacek  <polacek@redhat.com>
+
+	PR c/77490
+	* c.opt (Wbool-operation): New.
+
 2016-09-21  Bernd Edlinger  <bernd.edlinger@hotmail.de>

 	* c-common.c (c_common_truthvalue_conversion): Inhibit
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@ -315,6 +315,10 @@ Wbool-compare
 C ObjC C++ ObjC++ Var(warn_bool_compare) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
 Warn about boolean expression compared with an integer value different from true/false.

+Wbool-operation
+C ObjC C++ ObjC++ Var(warn_bool_op) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
+Warn about certain operations on boolean expressions.
+
 Wframe-address
 C ObjC C++ ObjC++ Var(warn_frame_address) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
 Warn when __builtin_frame_address or __builtin_return_address is used unsafely.
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@ -1,3 +1,9 @@
+2016-09-24  Marek Polacek  <polacek@redhat.com>
+
+	PR c/77490
+	* c-typeck.c (build_unary_op): Warn about bit not on expressions that
+	have boolean value.  Warn about ++/-- on booleans.
+
 2016-09-23  Jakub Jelinek  <jakub@redhat.com>

 	* c-parser.c (incomplete_record_decls): Remove unnecessary
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@ -4196,6 +4196,22 @@ build_unary_op (location_t location, enum tree_code code, tree xarg,
 	  || (typecode == VECTOR_TYPE
 	      && !VECTOR_FLOAT_TYPE_P (TREE_TYPE (arg))))
 	{
+	  tree e = arg;
+
+	  /* Warn if the expression has boolean value.  */
+	  while (TREE_CODE (e) == COMPOUND_EXPR)
+	    e = TREE_OPERAND (e, 1);
+
+	  if ((TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE
+	       || truth_value_p (TREE_CODE (e)))
+	      && warning_at (location, OPT_Wbool_operation,
+			     "%<~%> on a boolean expression"))
+	    {
+	      gcc_rich_location richloc (location);
+	      richloc.add_fixit_insert_before (location, "!");
+	      inform_at_rich_loc (&richloc, "did you mean to use logical "
+				  "not?");
+	    }
 	  if (!noconvert)
 	    arg = default_conversion (arg);
 	}
@ -4306,6 +4322,16 @@ build_unary_op (location_t location, enum tree_code code, tree xarg,
 			"decrement of enumeration value is invalid in C++");
 	}

+      if (TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE)
+	{
+	  if (code == PREINCREMENT_EXPR || code == POSTINCREMENT_EXPR)
+	    warning_at (location, OPT_Wbool_operation,
+			"increment of a boolean expression");
+	  else
+	    warning_at (location, OPT_Wbool_operation,
+			"decrement of a boolean expression");
+	}
+
      /* Ensure the argument is fully folded inside any SAVE_EXPR.  */
      arg = c_fully_fold (arg, false, NULL);

--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@ -1,3 +1,9 @@
+2016-09-24  Marek Polacek  <polacek@redhat.com>
+
+	PR c/77490
+	* typeck.c (cp_build_unary_op): Warn about bit not on expressions that
+	have boolean value.
+
 2016-09-23  Jakub Jelinek  <jakub@redhat.com>

 	Implement P0138R2, C++17 construction rules for enum class values
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@ -5792,6 +5792,7 @@ cp_build_unary_op (enum tree_code code, tree xarg, bool noconvert,
 {
  /* No default_conversion here.  It causes trouble for ADDR_EXPR.  */
  tree arg = xarg;
+  location_t location = EXPR_LOC_OR_LOC (arg, input_location);
  tree argtype = 0;
  const char *errstring = NULL;
  tree val;
@ -5853,7 +5854,14 @@ cp_build_unary_op (enum tree_code code, tree xarg, bool noconvert,
 						   arg, true)))
 	errstring = _("wrong type argument to bit-complement");
      else if (!noconvert && CP_INTEGRAL_TYPE_P (TREE_TYPE (arg)))
-	arg = cp_perform_integral_promotions (arg, complain);
+	{
+	  /* Warn if the expression has boolean value.  */
+	  if (TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE
+	      && warning_at (location, OPT_Wbool_operation,
+			     "%<~%> on an expression of type bool"))
+	    inform (location, "did you mean to use logical not (%<!%>)?");
+	  arg = cp_perform_integral_promotions (arg, complain);
+	}
      break;

    case ABS_EXPR:
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@ -256,8 +256,8 @@ Objective-C and Objective-C++ Dialects}.
 -pedantic-errors @gol
 -w  -Wextra  -Wall  -Waddress  -Waggregate-return  @gol
 -Wno-aggressive-loop-optimizations -Warray-bounds -Warray-bounds=@var{n} @gol
-Wno-attributes -Wbool-compare -Wno-builtin-macro-redefined @gol
-Wc90-c99-compat -Wc99-c11-compat @gol
+-Wno-attributes -Wbool-compare -Wbool-operation @gol
+-Wno-builtin-macro-redefined -Wc90-c99-compat -Wc99-c11-compat @gol
 -Wc++-compat -Wc++11-compat -Wc++14-compat -Wcast-align  -Wcast-qual  @gol
 -Wchar-subscripts -Wclobbered  -Wcomment -Wconditionally-supported  @gol
 -Wconversion -Wcoverage-mismatch -Wno-cpp -Wdangling-else -Wdate-time @gol
@ -3656,6 +3656,7 @@ Options} and @ref{Objective-C and Objective-C++ Dialect Options}.
@gccoptlist{-Waddress   @gol
 -Warray-bounds=1 @r{(only with} @option{-O2}@r{)}  @gol
 -Wbool-compare  @gol
+-Wbool-operation  @gol
 -Wc++11-compat  -Wc++14-compat@gol
 -Wchar-subscripts  @gol
 -Wcomment  @gol
@ -4846,6 +4847,17 @@ if ((n > 1) == 2) @{ @dots{} @}
@end smallexample
 This warning is enabled by @option{-Wall}.

+@item -Wbool-operation
+@opindex Wno-bool-operation
+@opindex Wbool-operation
+Warn about suspicious operations on expressions of a boolean type.  For
+instance, bitwise negation of a boolean is very likely a bug in the program.
+For C, this warning also warns about incrementing or decrementing a boolean,
+which rarely makes sense.  (In C++, decrementing a boolean is always invalid.
+Incrementing a boolean is invalid in C++1z, and deprecated otherwise.)
+
+This warning is enabled by @option{-Wall}.
+
@item -Wduplicated-cond
@opindex Wno-duplicated-cond
@opindex Wduplicated-cond
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@ -1,3 +1,9 @@
+2016-09-24  Marek Polacek  <polacek@redhat.com>
+
+	PR c/77490
+	* c-c++-common/Wbool-operation-1.c: New test.
+	* gcc.dg/Wbool-operation-1.c: New test.
+
 2016-09-23  Fritz Reese  <fritzoreese@gmail.com>

 	* gfortran.dg/dec_static_1.f90: New.
@ -10,7 +16,7 @@
 	PR fortran/48298
 	* gfortran.dg/negative_unit_check.f90: Update test.
 	* gfortran.dg/dtio_14.f90: New test.
-  
+
 2016-09-23  Dominik Vogt  <vogt@linux.vnet.ibm.com>

 	* gcc.target/s390/hotpatch-compile-1.c: Fixed dg-error test.
--- a/gcc/testsuite/c-c++-common/Wbool-operation-1.c
+++ b/gcc/testsuite/c-c++-common/Wbool-operation-1.c
@ -0,0 +1,36 @@
+/* PR c/77490 */
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+#ifndef __cplusplus
+# define bool _Bool
+#endif
+
+typedef volatile bool T;
+typedef int __attribute__ ((vector_size (4 * sizeof (int)))) v4si;
+extern bool foo (void);
+
+int
+fn (bool b, bool b2, T b3, int n, v4si v)
+{
+  int r = 0;
+
+  r += ~b; /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += n + ~b; /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += ~(n == 1); /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += ~(n || 1); /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += ~b == 1; /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += ~(++n, n == 1); /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += ~(++n, n > 1); /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += ~(++n, n && 1); /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += (++n, ~b); /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += ~b3; /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += ~foo (); /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+  r += ~(bool) !1; /* { dg-warning "on an expression of type bool|on a boolean expression" } */
+
+  v = ~v;
+  r += ~(int) b;
+  r += -b;
+
+  return r;
+}
--- a/gcc/testsuite/gcc.dg/Wbool-operation-1.c
+++ b/gcc/testsuite/gcc.dg/Wbool-operation-1.c
@ -0,0 +1,16 @@
+/* PR c/77490 */
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+int
+fn (_Bool b)
+{
+  int r = 0;
+
+  r += b++; /* { dg-warning "increment of a boolean expression" } */
+  r += ++b; /* { dg-warning "increment of a boolean expression" } */
+  r += b--; /* { dg-warning "decrement of a boolean expression" } */
+  r += --b; /* { dg-warning "decrement of a boolean expression" } */
+
+  return r;
+}