Hi, I have some comments/questions in-line:
On 9/15/16, Marek Polacek <pola...@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 <pola...@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
