C/C++ PATCH to implement -Wbool-operation (PR c/77490)

C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Marek Polacek]

Now that the C++ FE boolean in/decrement changes are in, I can move forwards
with this patch which implements a new warning named -Wbool-operation (better
names?) which warns about nonsensical code such as ~bool, ~(i == 10), or
bool-- (in C).

It could also warn for other operations such as * or / or <<, but I wasn't
sure about those, so this isn't included in this patch. 

Bootstrapped/regtested on x86_64-linux and ppc64-linux, ok for trunk?

2016-09-15  Marek Polacek  <polacek@redhat.com>

	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/Wall.c: Use -Wno-bool-operation.
	* gcc.dg/Wbool-operation-1.c: New test.

diff --git gcc/c-family/c.opt gcc/c-family/c.opt
index c55c7c3..fb6f2d1 100644
--- gcc/c-family/c.opt
+++ 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.
diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index 4dec397..c455d22 100644
--- gcc/c/c-typeck.c
+++ 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);
 
diff --git gcc/cp/typeck.c gcc/cp/typeck.c
index c53a85a..9fc1a4b 100644
--- gcc/cp/typeck.c
+++ gcc/cp/typeck.c
@@ -5853,7 +5853,16 @@ 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.  */
+	  location_t location = EXPR_LOC_OR_LOC (arg, input_location);
+	  if ((TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE
+	       || truth_value_p (TREE_CODE (arg)))
+	      && warning_at (location, OPT_Wbool_operation,
+			     "%<~%> on a boolean expression"))
+	    inform (location, "did you mean to use logical not (%<!%>)?");
+	  arg = cp_perform_integral_promotions (arg, complain);
+	}
       break;
 
     case ABS_EXPR:
diff --git gcc/doc/invoke.texi gcc/doc/invoke.texi
index 8eb5eff..976e137 100644
--- gcc/doc/invoke.texi
+++ 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
@@ -3654,6 +3654,7 @@ 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
@@ -4761,6 +4762,16 @@ 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.
+
+This warning is enabled by @option{-Wall}.
+
 @item -Wduplicated-cond
 @opindex Wno-duplicated-cond
 @opindex Wduplicated-cond
diff --git gcc/testsuite/c-c++-common/Wbool-operation-1.c gcc/testsuite/c-c++-common/Wbool-operation-1.c
index e69de29..287bd03 100644
--- gcc/testsuite/c-c++-common/Wbool-operation-1.c
+++ gcc/testsuite/c-c++-common/Wbool-operation-1.c
@@ -0,0 +1,37 @@
+/* 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 a boolean expression" } */
+  r += n + ~b; /* { dg-warning "on a boolean expression" } */
+  r += ~(n == 1); /* { dg-warning "on a boolean expression" } */
+  r += ~(n || 1); /* { dg-warning "on a boolean expression" } */
+  r += ~b == 1; /* { dg-warning "on a boolean expression" } */
+  r += ~(++n, n == 1); /* { dg-warning "on a boolean expression" } */
+  r += ~(++n, n > 1); /* { dg-warning "on a boolean expression" } */
+  r += ~(++n, n && 1); /* { dg-warning "on a boolean expression" } */
+  r += (++n, ~b); /* { dg-warning "on a boolean expression" } */
+  r += (++n, n + ~b); /* { dg-warning "on a boolean expression" } */
+  r += ~b3; /* { dg-warning "on a boolean expression" } */
+  r += ~foo (); /* { dg-warning "on a boolean expression" } */
+  r += ~(bool) !1; /* { dg-warning "on a boolean expression" } */
+
+  v = ~v;
+  r += ~(int) b;
+  r += -b;
+
+  return r;
+}
diff --git gcc/testsuite/gcc.dg/Wall.c gcc/testsuite/gcc.dg/Wall.c
index 8984847..6c73533 100644
--- gcc/testsuite/gcc.dg/Wall.c
+++ gcc/testsuite/gcc.dg/Wall.c
@@ -1,7 +1,7 @@
 /* PR 30437: Test -Wall 
    Don't change this without changing Wno-all.c as well.  */
 /* { dg-do compile } */
-/* { dg-options "-Wall" } */
+/* { dg-options "-Wall -Wno-bool-operation" } */
 
 void foo(int a)
 {
diff --git gcc/testsuite/gcc.dg/Wbool-operation-1.c gcc/testsuite/gcc.dg/Wbool-operation-1.c
index e69de29..b24e763 100644
--- gcc/testsuite/gcc.dg/Wbool-operation-1.c
+++ 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;
+}

	Marek

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Eric Gallager]

Hi, I have some comments/questions in-line:

On 9/15/16, Marek Polacek <polacek@redhat.com> wrote:
> Now that the C++ FE boolean in/decrement changes are in, I can move
> forwards with this patch which implements a new warning named -Wbool-operation
> (better names?) which warns about nonsensical code such as ~bool, ~(i == 10), or
> bool-- (in C).
>
> It could also warn for other operations such as * or / or <<, but I wasn't
> sure about those, so this isn't included in this patch.
>
> Bootstrapped/regtested on x86_64-linux and ppc64-linux, ok for trunk?
>
> 2016-09-15  Marek Polacek  <polacek@redhat.com>
>
> 	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/Wall.c: Use -Wno-bool-operation.
> 	* gcc.dg/Wbool-operation-1.c: New test.
>
> diff --git gcc/c-family/c.opt gcc/c-family/c.opt
> index c55c7c3..fb6f2d1 100644
> --- gcc/c-family/c.opt
> +++ 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.
> diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
> index 4dec397..c455d22 100644
> --- gcc/c/c-typeck.c
> +++ 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);
>
> diff --git gcc/cp/typeck.c gcc/cp/typeck.c
> index c53a85a..9fc1a4b 100644
> --- gcc/cp/typeck.c
> +++ gcc/cp/typeck.c
> @@ -5853,7 +5853,16 @@ 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.  */
> +	  location_t location = EXPR_LOC_OR_LOC (arg, input_location);
> +	  if ((TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE
> +	       || truth_value_p (TREE_CODE (arg)))
> +	      && warning_at (location, OPT_Wbool_operation,
> +			     "%<~%> on a boolean expression"))
> +	    inform (location, "did you mean to use logical not (%<!%>)?");
> +	  arg = cp_perform_integral_promotions (arg, complain);
> +	}
>        break;
>
>      case ABS_EXPR:
> diff --git gcc/doc/invoke.texi gcc/doc/invoke.texi
> index 8eb5eff..976e137 100644
> --- gcc/doc/invoke.texi
> +++ 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
> @@ -3654,6 +3654,7 @@ 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
> @@ -4761,6 +4762,16 @@ 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.
> +


I'd also mention that C++ now warns about incrementing and
decrementing anyways, even without this option.


> +This warning is enabled by @option{-Wall}.
> +
>  @item -Wduplicated-cond
>  @opindex Wno-duplicated-cond
>  @opindex Wduplicated-cond
> diff --git gcc/testsuite/c-c++-common/Wbool-operation-1.c
> gcc/testsuite/c-c++-common/Wbool-operation-1.c
> index e69de29..287bd03 100644
> --- gcc/testsuite/c-c++-common/Wbool-operation-1.c
> +++ gcc/testsuite/c-c++-common/Wbool-operation-1.c
> @@ -0,0 +1,37 @@
> +/* 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 a boolean expression" } */
> +  r += n + ~b; /* { dg-warning "on a boolean expression" } */
> +  r += ~(n == 1); /* { dg-warning "on a boolean expression" } */
> +  r += ~(n || 1); /* { dg-warning "on a boolean expression" } */
> +  r += ~b == 1; /* { dg-warning "on a boolean expression" } */
> +  r += ~(++n, n == 1); /* { dg-warning "on a boolean expression" } */
> +  r += ~(++n, n > 1); /* { dg-warning "on a boolean expression" } */
> +  r += ~(++n, n && 1); /* { dg-warning "on a boolean expression" } */
> +  r += (++n, ~b); /* { dg-warning "on a boolean expression" } */
> +  r += (++n, n + ~b); /* { dg-warning "on a boolean expression" } */
> +  r += ~b3; /* { dg-warning "on a boolean expression" } */
> +  r += ~foo (); /* { dg-warning "on a boolean expression" } */
> +  r += ~(bool) !1; /* { dg-warning "on a boolean expression" } */
> +
> +  v = ~v;
> +  r += ~(int) b;
> +  r += -b;
> +
> +  return r;
> +}
> diff --git gcc/testsuite/gcc.dg/Wall.c gcc/testsuite/gcc.dg/Wall.c
> index 8984847..6c73533 100644
> --- gcc/testsuite/gcc.dg/Wall.c
> +++ gcc/testsuite/gcc.dg/Wall.c
> @@ -1,7 +1,7 @@
>  /* PR 30437: Test -Wall
>     Don't change this without changing Wno-all.c as well.  */
>  /* { dg-do compile } */
> -/* { dg-options "-Wall" } */
> +/* { dg-options "-Wall -Wno-bool-operation" } */
>


Why did -Wno-bool-operation need to be added here?


>  void foo(int a)
>  {
> diff --git gcc/testsuite/gcc.dg/Wbool-operation-1.c
> gcc/testsuite/gcc.dg/Wbool-operation-1.c
> index e69de29..b24e763 100644
> --- gcc/testsuite/gcc.dg/Wbool-operation-1.c
> +++ 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;
> +}
>
> 	Marek
>


Anyways, thanks for your work on this; I hope it goes in soon!


Eric

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Marek Polacek]

On Thu, Sep 15, 2016 at 04:45:03PM -0400, Eric Gallager wrote:
> > +@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.
> > +
> 
> 
> I'd also mention that C++ now warns about incrementing and
> decrementing anyways, even without this option.

Ok, I could have added that.  Done now.

> > --- gcc/testsuite/gcc.dg/Wall.c
> > +++ gcc/testsuite/gcc.dg/Wall.c
> > @@ -1,7 +1,7 @@
> >  /* PR 30437: Test -Wall
> >     Don't change this without changing Wno-all.c as well.  */
> >  /* { dg-do compile } */
> > -/* { dg-options "-Wall" } */
> > +/* { dg-options "-Wall -Wno-bool-operation" } */
> >
> 
> 
> Why did -Wno-bool-operation need to be added here?

Oops, that is a mistake.  This is a remnant from the previous version.
Removed.

> Anyways, thanks for your work on this; I hope it goes in soon!

Thanks.

Bootstrapped/regtested on x86_64-linux and ppc64-linux, ok for trunk?

2016-09-16  Marek Polacek  <polacek@redhat.com>

	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.

diff --git gcc/c-family/c.opt gcc/c-family/c.opt
index c55c7c3..fb6f2d1 100644
--- gcc/c-family/c.opt
+++ 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.
diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index 4dec397..c455d22 100644
--- gcc/c/c-typeck.c
+++ 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);
 
diff --git gcc/cp/typeck.c gcc/cp/typeck.c
index c53a85a..9fc1a4b 100644
--- gcc/cp/typeck.c
+++ gcc/cp/typeck.c
@@ -5853,7 +5853,16 @@ 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.  */
+	  location_t location = EXPR_LOC_OR_LOC (arg, input_location);
+	  if ((TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE
+	       || truth_value_p (TREE_CODE (arg)))
+	      && warning_at (location, OPT_Wbool_operation,
+			     "%<~%> on a boolean expression"))
+	    inform (location, "did you mean to use logical not (%<!%>)?");
+	  arg = cp_perform_integral_promotions (arg, complain);
+	}
       break;
 
     case ABS_EXPR:
diff --git gcc/doc/invoke.texi gcc/doc/invoke.texi
index 8eb5eff..1c3ca3f 100644
--- gcc/doc/invoke.texi
+++ 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
@@ -3654,6 +3654,7 @@ 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
@@ -4761,6 +4762,17 @@ 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
diff --git gcc/testsuite/c-c++-common/Wbool-operation-1.c gcc/testsuite/c-c++-common/Wbool-operation-1.c
index e69de29..287bd03 100644
--- gcc/testsuite/c-c++-common/Wbool-operation-1.c
+++ gcc/testsuite/c-c++-common/Wbool-operation-1.c
@@ -0,0 +1,37 @@
+/* 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 a boolean expression" } */
+  r += n + ~b; /* { dg-warning "on a boolean expression" } */
+  r += ~(n == 1); /* { dg-warning "on a boolean expression" } */
+  r += ~(n || 1); /* { dg-warning "on a boolean expression" } */
+  r += ~b == 1; /* { dg-warning "on a boolean expression" } */
+  r += ~(++n, n == 1); /* { dg-warning "on a boolean expression" } */
+  r += ~(++n, n > 1); /* { dg-warning "on a boolean expression" } */
+  r += ~(++n, n && 1); /* { dg-warning "on a boolean expression" } */
+  r += (++n, ~b); /* { dg-warning "on a boolean expression" } */
+  r += (++n, n + ~b); /* { dg-warning "on a boolean expression" } */
+  r += ~b3; /* { dg-warning "on a boolean expression" } */
+  r += ~foo (); /* { dg-warning "on a boolean expression" } */
+  r += ~(bool) !1; /* { dg-warning "on a boolean expression" } */
+
+  v = ~v;
+  r += ~(int) b;
+  r += -b;
+
+  return r;
+}
diff --git gcc/testsuite/gcc.dg/Wbool-operation-1.c gcc/testsuite/gcc.dg/Wbool-operation-1.c
index e69de29..b24e763 100644
--- gcc/testsuite/gcc.dg/Wbool-operation-1.c
+++ 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;
+}

	Marek

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Jason Merrill]

On 09/16/2016 05:01 AM, Marek Polacek wrote:
> @@ -5853,7 +5853,16 @@ 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.  */
> +	  location_t location = EXPR_LOC_OR_LOC (arg, input_location);

Let's move this variable to the beginning of the function; hopefully it 
will become a parameter soon.

> +	  if ((TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE
> +	       || truth_value_p (TREE_CODE (arg)))

You shouldn't need to check truth_value_p; in C++ all truth operations 
have type bool.

> +	      && warning_at (location, OPT_Wbool_operation,
> +			     "%<~%> on a boolean expression"))

And let's refer to "expression of type bool" rather than "boolean 
expression".

Jason

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Marek Polacek]

On Mon, Sep 19, 2016 at 02:41:04PM -0400, Jason Merrill wrote:
> On 09/16/2016 05:01 AM, Marek Polacek wrote:
> > @@ -5853,7 +5853,16 @@ 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.  */
> > +	  location_t location = EXPR_LOC_OR_LOC (arg, input_location);
> 
> Let's move this variable to the beginning of the function; hopefully it will
> become a parameter soon.
 
Done.

> > +	  if ((TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE
> > +	       || truth_value_p (TREE_CODE (arg)))
> 
> You shouldn't need to check truth_value_p; in C++ all truth operations have
> type bool.

Oops, force of habit...

> > +	      && warning_at (location, OPT_Wbool_operation,
> > +			     "%<~%> on a boolean expression"))
> 
> And let's refer to "expression of type bool" rather than "boolean
> expression".

Adjusted (and in the C FE too).

Bootstrapped/regtested on x86_64-linux and ppc64-linux, ok for trunk?

2016-09-20  Marek Polacek  <polacek@redhat.com>

	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.

diff --git gcc/c-family/c.opt gcc/c-family/c.opt
index 6cf915d..0e8d68a 100644
--- gcc/c-family/c.opt
+++ 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.
diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index 059ad1f..4006b1a 100644
--- gcc/c/c-typeck.c
+++ 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 an expression of type bool"))
+	    {
+	      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 an expression of type bool");
+	  else
+	    warning_at (location, OPT_Wbool_operation,
+			"decrement of an expression of type bool");
+	}
+
       /* Ensure the argument is fully folded inside any SAVE_EXPR.  */
       arg = c_fully_fold (arg, false, NULL);
 
diff --git gcc/cp/typeck.c gcc/cp/typeck.c
index c53a85a..dee17b3 100644
--- gcc/cp/typeck.c
+++ 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:
diff --git gcc/doc/invoke.texi gcc/doc/invoke.texi
index 3c27283..6e8218c 100644
--- gcc/doc/invoke.texi
+++ 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
@@ -3654,6 +3654,7 @@ 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
@@ -4762,6 +4763,17 @@ 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
diff --git gcc/testsuite/c-c++-common/Wbool-operation-1.c gcc/testsuite/c-c++-common/Wbool-operation-1.c
index e69de29..e81e89d 100644
--- gcc/testsuite/c-c++-common/Wbool-operation-1.c
+++ gcc/testsuite/c-c++-common/Wbool-operation-1.c
@@ -0,0 +1,37 @@
+/* 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" } */
+  r += n + ~b; /* { dg-warning "on an expression of type bool" } */
+  r += ~(n == 1); /* { dg-warning "on an expression of type bool" } */
+  r += ~(n || 1); /* { dg-warning "on an expression of type bool" } */
+  r += ~b == 1; /* { dg-warning "on an expression of type bool" } */
+  r += ~(++n, n == 1); /* { dg-warning "on an expression of type bool" } */
+  r += ~(++n, n > 1); /* { dg-warning "on an expression of type bool" } */
+  r += ~(++n, n && 1); /* { dg-warning "on an expression of type bool" } */
+  r += (++n, ~b); /* { dg-warning "on an expression of type bool" } */
+  r += (++n, n + ~b); /* { dg-warning "on an expression of type bool" } */
+  r += ~b3; /* { dg-warning "on an expression of type bool" } */
+  r += ~foo (); /* { dg-warning "on an expression of type bool" } */
+  r += ~(bool) !1; /* { dg-warning "on an expression of type bool" } */
+
+  v = ~v;
+  r += ~(int) b;
+  r += -b;
+
+  return r;
+}
diff --git gcc/testsuite/gcc.dg/Wbool-operation-1.c gcc/testsuite/gcc.dg/Wbool-operation-1.c
index e69de29..f3acc54 100644
--- gcc/testsuite/gcc.dg/Wbool-operation-1.c
+++ 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 an expression of type bool" } */
+  r += ++b; /* { dg-warning "increment of an expression of type bool" } */
+  r += b--; /* { dg-warning "decrement of an expression of type bool" } */
+  r += --b; /* { dg-warning "decrement of an expression of type bool" } */
+
+  return r;
+}

	Marek

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Jason Merrill]

On 09/20/2016 01:13 PM, Marek Polacek wrote:
> On Mon, Sep 19, 2016 at 02:41:04PM -0400, Jason Merrill wrote:
>> On 09/16/2016 05:01 AM, Marek Polacek wrote:
>>> @@ -5853,7 +5853,16 @@ 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.  */
>>> +	  location_t location = EXPR_LOC_OR_LOC (arg, input_location);
>>
>> Let's move this variable to the beginning of the function; hopefully it will
>> become a parameter soon.
>
> Done.
>
>>> +	  if ((TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE
>>> +	       || truth_value_p (TREE_CODE (arg)))
>>
>> You shouldn't need to check truth_value_p; in C++ all truth operations have
>> type bool.
>
> Oops, force of habit...
>
>>> +	      && warning_at (location, OPT_Wbool_operation,
>>> +			     "%<~%> on a boolean expression"))
>>
>> And let's refer to "expression of type bool" rather than "boolean
>> expression".
>
> Adjusted (and in the C FE too).

Hmm, I'm not sure that change is right for C.  But the C++ hunk is OK.

Jason

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Marek Polacek]

On Wed, Sep 21, 2016 at 11:37:32AM -0400, Jason Merrill wrote:
> On 09/20/2016 01:13 PM, Marek Polacek wrote:
> > On Mon, Sep 19, 2016 at 02:41:04PM -0400, Jason Merrill wrote:
> > > On 09/16/2016 05:01 AM, Marek Polacek wrote:
> > > > @@ -5853,7 +5853,16 @@ 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.  */
> > > > +	  location_t location = EXPR_LOC_OR_LOC (arg, input_location);
> > > 
> > > Let's move this variable to the beginning of the function; hopefully it will
> > > become a parameter soon.
> > 
> > Done.
> > 
> > > > +	  if ((TREE_CODE (TREE_TYPE (arg)) == BOOLEAN_TYPE
> > > > +	       || truth_value_p (TREE_CODE (arg)))
> > > 
> > > You shouldn't need to check truth_value_p; in C++ all truth operations have
> > > type bool.
> > 
> > Oops, force of habit...
> > 
> > > > +	      && warning_at (location, OPT_Wbool_operation,
> > > > +			     "%<~%> on a boolean expression"))
> > > 
> > > And let's refer to "expression of type bool" rather than "boolean
> > > expression".
> > 
> > Adjusted (and in the C FE too).
> 
> Hmm, I'm not sure that change is right for C.  But the C++ hunk is OK.

Thanks.  Joseph, how about the C part?

	Marek

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Joseph Myers]

On Wed, 21 Sep 2016, Marek Polacek wrote:

> > > > And let's refer to "expression of type bool" rather than "boolean
> > > > expression".
> > > 
> > > Adjusted (and in the C FE too).
> > 
> > Hmm, I'm not sure that change is right for C.  But the C++ hunk is OK.
> 
> Thanks.  Joseph, how about the C part?

You shouldn't refer to "type bool" for C.  If it's the result of a boolean 
operation, the type is int; an expression has type _Bool only if cast to 
that type or if it's a variable of that type.

-- 
Joseph S. Myers
joseph@codesourcery.com

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Marek Polacek]

On Thu, Sep 22, 2016 at 05:24:31PM +0000, Joseph Myers wrote:
> On Wed, 21 Sep 2016, Marek Polacek wrote:
> 
> > > > > And let's refer to "expression of type bool" rather than "boolean
> > > > > expression".
> > > > 
> > > > Adjusted (and in the C FE too).
> > > 
> > > Hmm, I'm not sure that change is right for C.  But the C++ hunk is OK.
> > 
> > Thanks.  Joseph, how about the C part?
> 
> You shouldn't refer to "type bool" for C.  If it's the result of a boolean 
> operation, the type is int; an expression has type _Bool only if cast to 
> that type or if it's a variable of that type.

Ok, so how about this one?

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2016-09-23  Marek Polacek  <polacek@redhat.com>

	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.

diff --git gcc/c-family/c.opt gcc/c-family/c.opt
index a04618d..4a9b9e8 100644
--- gcc/c-family/c.opt
+++ 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.
diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index 059ad1f..e5c7256 100644
--- gcc/c/c-typeck.c
+++ 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);
 
diff --git gcc/cp/typeck.c gcc/cp/typeck.c
index c53a85a..dee17b3 100644
--- gcc/cp/typeck.c
+++ 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:
diff --git gcc/doc/invoke.texi gcc/doc/invoke.texi
index e6f503f..a5481b5 100644
--- gcc/doc/invoke.texi
+++ 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
diff --git gcc/testsuite/c-c++-common/Wbool-operation-1.c gcc/testsuite/c-c++-common/Wbool-operation-1.c
index e69de29..bb72784 100644
--- gcc/testsuite/c-c++-common/Wbool-operation-1.c
+++ 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;
+}
diff --git gcc/testsuite/gcc.dg/Wbool-operation-1.c gcc/testsuite/gcc.dg/Wbool-operation-1.c
index e69de29..b24e763 100644
--- gcc/testsuite/gcc.dg/Wbool-operation-1.c
+++ 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;
+}

	Marek

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Joseph Myers]

On Fri, 23 Sep 2016, Marek Polacek wrote:

> On Thu, Sep 22, 2016 at 05:24:31PM +0000, Joseph Myers wrote:
> > On Wed, 21 Sep 2016, Marek Polacek wrote:
> > 
> > > > > > And let's refer to "expression of type bool" rather than "boolean
> > > > > > expression".
> > > > > 
> > > > > Adjusted (and in the C FE too).
> > > > 
> > > > Hmm, I'm not sure that change is right for C.  But the C++ hunk is OK.
> > > 
> > > Thanks.  Joseph, how about the C part?
> > 
> > You shouldn't refer to "type bool" for C.  If it's the result of a boolean 
> > operation, the type is int; an expression has type _Bool only if cast to 
> > that type or if it's a variable of that type.
> 
> Ok, so how about this one?

The C changes here are OK.

-- 
Joseph S. Myers
joseph@codesourcery.com

Re: C/C++ PATCH to implement -Wbool-operation (PR c/77490)

[Marek Polacek]

On Sat, Oct 01, 2016 at 01:46:02AM +0200, Jakub Jelinek wrote:
> On Fri, Sep 23, 2016 at 12:44:22PM +0200, Marek Polacek wrote:
> > 2016-09-23  Marek Polacek  <polacek@redhat.com>
> > 
> > 	PR c/77490
> ...
> > 	* c-c++-common/Wbool-operation-1.c: New test.
> 
> I've noticed this test fails on i686-linux and likely also on powerpc-linux.

Sorry.  I must remember this when testing sth with vectors...

	Marek