[RFC PATCH] -Wmemset-transposed-args (PR middle-end/61294)
Richard Biener
richard.guenther@gmail.com
Wed Jul 9 10:51:00 GMT 2014
On Wed, Jul 9, 2014 at 12:32 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Wed, Jul 09, 2014 at 12:26:09PM +0200, Richard Biener wrote:
>> > I suppose we could use an INTEGER_CST distinct from the one in
>> > TYPE_CACHED_VALUES for raw 0, with a TREE_LANG_FLAG set.
>>
>> Ick. (please no - at least make sure it doesn't survive anywhere to the
>> middle-end, like fold or gimple).
>
> Why? I don't think the middle-end ever compares INTEGER_CSTs for equality.
At least it shouldn't (they are not required to be shared and usually are not
if they've gone a transition from TREE_OVERFLOW to !TREE_OVERFLOW).
Well, still feels ugly to me - but it's Jasons call in the end.
Richard.
> Here is my WIP on Jason's suggestion (untested of course other than the
> testcase), the C++ FE is changed to do that, the C FE is not.
>
> Sure, I could add another bool argument to
> cp_parser_parenthesized_expression_list whether the caller expects to see
> the literal zeros, and replace them with normal INTEGER_CSTs after the test.
>
> --- gcc/c/c-typeck.c.jj 2014-07-08 17:38:09.612266656 +0200
> +++ gcc/c/c-typeck.c 2014-07-09 10:41:38.931018088 +0200
> @@ -2987,6 +2987,16 @@ c_build_function_call_vec (location_t lo
> /* Convert anything with function type to a pointer-to-function. */
> if (TREE_CODE (function) == FUNCTION_DECL)
> {
> + if (warn_memset_transposed_args
> + && DECL_BUILT_IN_CLASS (function) == BUILT_IN_NORMAL
> + && DECL_FUNCTION_CODE (function) == BUILT_IN_MEMSET
> + && vec_safe_length (params) == 3
> + && integer_zerop ((*params)[2])
> + && !integer_zerop ((*params)[1]))
> + warning_at (loc, OPT_Wmemset_transposed_args,
> + "%<memset%> used with constant zero length parameter; "
> + "this could be due to transposed parameters");
> +
> /* Implement type-directed function overloading for builtins.
> resolve_overloaded_builtin and targetm.resolve_overloaded_builtin
> handle all the type checking. The result is a complete expression
> --- gcc/cp/cp-tree.h.jj 2014-07-07 10:39:44.000000000 +0200
> +++ gcc/cp/cp-tree.h 2014-07-09 11:48:12.534274257 +0200
> @@ -4187,6 +4187,10 @@ more_aggr_init_expr_args_p (const aggr_i
> #define SIZEOF_EXPR_TYPE_P(NODE) \
> TREE_LANG_FLAG_0 (SIZEOF_EXPR_CHECK (NODE))
>
> +/* True if INTEGER_CST is a zero literal seen in function argument list. */
> +#define LITERAL_ZERO_P(NODE) \
> + (INTEGER_CST_CHECK (NODE)->base.nothrow_flag)
> +
> /* An enumeration of the kind of tags that C++ accepts. */
> enum tag_types {
> none_type = 0, /* Not a tag type. */
> --- gcc/cp/parser.c.jj 2014-07-09 10:41:12.000000000 +0200
> +++ gcc/cp/parser.c 2014-07-09 11:36:40.195693369 +0200
> @@ -6142,6 +6142,19 @@ cp_parser_postfix_expression (cp_parser
> }
> }
>
> + if (warn_memset_transposed_args
> + && TREE_CODE (postfix_expression) == FUNCTION_DECL
> + && DECL_BUILT_IN_CLASS (postfix_expression) == BUILT_IN_NORMAL
> + && DECL_FUNCTION_CODE (postfix_expression) == BUILT_IN_MEMSET
> + && vec_safe_length (args) == 3
> + && integer_zerop ((*args)[2])
> + && LITERAL_ZERO_P ((*args)[2])
> + && !(integer_zerop ((*args)[1])
> + && LITERAL_ZERO_P ((*args)[1])))
> + warning (OPT_Wmemset_transposed_args,
> + "%<memset%> used with constant zero length parameter; "
> + "this could be due to transposed parameters");
> +
> if (TREE_CODE (postfix_expression) == COMPONENT_REF)
> {
> tree instance = TREE_OPERAND (postfix_expression, 0);
> @@ -6630,6 +6643,10 @@ cp_parser_postfix_dot_deref_expression (
> return postfix_expression;
> }
>
> +/* Cache of LITERAL_ZERO_P constants. */
> +
> +static GTY(()) tree literal_zeros[itk_none];
> +
> /* Parse a parenthesized expression-list.
>
> expression-list:
> @@ -6724,7 +6741,50 @@ cp_parser_parenthesized_expression_list
> *non_constant_p = true;
> }
> else
> - expr = cp_parser_assignment_expression (parser, cast_p, NULL);
> + {
> + expr = NULL_TREE;
> + cp_token *tok = cp_lexer_peek_token (parser->lexer);
> + switch (tok->type)
> + {
> + case CPP_NUMBER:
> + case CPP_CHAR:
> + case CPP_WCHAR:
> + case CPP_CHAR16:
> + case CPP_CHAR32:
> + /* If a parameter is literal zero alone, remember it
> + for -Wmemset-transposed-args warning. */
> + if (integer_zerop (tok->u.value)
> + && !TREE_OVERFLOW (tok->u.value)
> + && is_attribute_list == non_attr
> + && (cp_lexer_peek_nth_token (parser->lexer, 2)->type
> + == CPP_COMMA
> + || cp_lexer_peek_nth_token (parser->lexer, 2)->type
> + == CPP_CLOSE_PAREN))
> + {
> + unsigned int i;
> + for (i = 0; i < itk_none; ++i)
> + if (TREE_TYPE (tok->u.value) == integer_types[i])
> + break;
> + if (i < itk_none && literal_zeros[i])
> + expr = literal_zeros[i];
> + else
> + {
> + expr = copy_node (tok->u.value);
> + LITERAL_ZERO_P (expr) = 1;
> + if (i < itk_none)
> + literal_zeros[i] = expr;
> + }
> + /* Consume the 0 token (or '\0', 0LL etc.). */
> + cp_lexer_consume_token (parser->lexer);
> + }
> + break;
> + default:
> + break;
> + }
> + if (expr == NULL_TREE)
> + expr = cp_parser_assignment_expression (parser, cast_p,
> + NULL);
> + }
>
> if (fold_expr_p)
> expr = fold_non_dependent_expr (expr);
> --- gcc/doc/invoke.texi.jj 2014-07-08 17:38:09.301268037 +0200
> +++ gcc/doc/invoke.texi 2014-07-09 10:41:38.950017994 +0200
> @@ -257,8 +257,8 @@ Objective-C and Objective-C++ Dialects}.
> -Wno-int-to-pointer-cast -Wno-invalid-offsetof @gol
> -Winvalid-pch -Wlarger-than=@var{len} -Wunsafe-loop-optimizations @gol
> -Wlogical-op -Wlogical-not-parentheses -Wlong-long @gol
> --Wmain -Wmaybe-uninitialized -Wmissing-braces -Wmissing-field-initializers @gol
> --Wmissing-include-dirs @gol
> +-Wmain -Wmaybe-uninitialized -Wmemset-transposed-args -Wmissing-braces @gol
> +-Wmissing-field-initializers -Wmissing-include-dirs @gol
> -Wno-multichar -Wnonnull -Wno-overflow -Wopenmp-simd @gol
> -Woverlength-strings -Wpacked -Wpacked-bitfield-compat -Wpadded @gol
> -Wparentheses -Wpedantic-ms-format -Wno-pedantic-ms-format @gol
> @@ -4683,6 +4683,15 @@ Warn when the @code{sizeof} operator is
> declared as an array in a function definition. This warning is enabled by
> default for C and C++ programs.
>
> +@item -Wmemset-transposed-args
> +@opindex Wmemset-transposed-args
> +@opindex Wno-memset-transposed-args
> +Warn for suspicious calls to the memset built-in function, if the
> +second argument is not zero and third argument is zero. This warns e.g.@
> +about @code{memset (buf, sizeof buf, 0);} where most probably
> +@code{memset (buf, 0, sizeof buf);} was meant instead. This warning is
> +enabled by @option{-Wall}.
> +
> @item -Waddress
> @opindex Waddress
> @opindex Wno-address
> --- gcc/testsuite/g++.dg/warn/Wmemset-transposed-args-1.C.jj 2014-07-09 10:41:38.969017900 +0200
> +++ gcc/testsuite/g++.dg/warn/Wmemset-transposed-args-1.C 2014-07-09 12:12:40.850993778 +0200
> @@ -0,0 +1,74 @@
> +// { dg-do compile }
> +// { dg-options "-Wall" }
> +
> +typedef __SIZE_TYPE__ size_t;
> +extern "C" void *memset (void *, int, size_t);
> +char buf[1024];
> +namespace std
> +{
> + extern "C" void *memset (void *, int, size_t);
> +}
> +
> +template <int N>
> +void
> +foo ()
> +{
> + memset (buf, sizeof buf, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, '\0'); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, L'\0'); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, N);
> + memset (buf, 1, 1 - 1);
> + memset (buf, 1, 0 - 0);
> + memset (buf, 1, N - N);
> + memset (buf, 0, 0);
> + memset (buf, 1 - 1, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, 0 - 0, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, 0L); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, 0UL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, 0LL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, 0ULL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, (int) 0);
> + memset (buf, sizeof buf, -0);
> +}
> +
> +template <int N>
> +void
> +baz ()
> +{
> + std::memset (buf, sizeof buf, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, '\0'); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, L'\0'); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, N);
> + std::memset (buf, 1, 1 - 1);
> + std::memset (buf, 1, 0 - 0);
> + std::memset (buf, 1, N - N);
> + std::memset (buf, 0, 0);
> + std::memset (buf, 1 - 1, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, 0 - 0, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, 0L); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, 0UL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, 0LL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, 0ULL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, (int) 0);
> + std::memset (buf, sizeof buf, -0);
> +}
> +
> +void
> +bar ()
> +{
> + foo<0> ();
> + std::memset (buf, sizeof buf, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, '\0'); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, L'\0'); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, 1, 1 - 1);
> + std::memset (buf, 1, 0 - 0);
> + std::memset (buf, 0, 0);
> + std::memset (buf, 1 - 1, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, 0 - 0, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, 0L); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, 0UL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, 0LL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, 0ULL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + std::memset (buf, sizeof buf, (int) 0);
> + std::memset (buf, sizeof buf, -0);
> +}
> --- gcc/testsuite/c-c++-common/Wmemset-transposed-args1.c.jj 2014-07-09 10:41:38.969017900 +0200
> +++ gcc/testsuite/c-c++-common/Wmemset-transposed-args1.c 2014-07-09 11:51:12.000000000 +0200
> @@ -0,0 +1,29 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Wall" } */
> +
> +typedef __SIZE_TYPE__ size_t;
> +extern
> +#ifdef __cplusplus
> +"C"
> +#endif
> +void *memset (void *, int, size_t);
> +char buf[1024];
> +
> +void
> +foo ()
> +{
> + memset (buf, sizeof buf, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, '\0'); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, L'\0'); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, 1, 1 - 1);
> + memset (buf, 1, 0 - 0);
> + memset (buf, 0, 0);
> + memset (buf, 1 - 1, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, 0 - 0, 0); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, 0L); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, 0UL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, 0LL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, 0ULL); /* { dg-warning ".memset. used with constant zero length parameter; this could be due to transposed parameters" } */
> + memset (buf, sizeof buf, (int) 0);
> + memset (buf, sizeof buf, -0);
> +}
> --- gcc/c-family/c.opt.jj 2014-07-08 17:38:09.249268240 +0200
> +++ gcc/c-family/c.opt 2014-07-09 10:41:38.909018201 +0200
> @@ -518,6 +518,10 @@ Wmain
> LangEnabledBy(C ObjC C++ ObjC++,Wpedantic, 2, 0)
> ;
>
> +Wmemset-transposed-args
> +C ObjC C++ ObjC++ Var(warn_memset_transposed_args) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
> +Warn about suspicious call to memset where the third argument is constant zero and second is not zero
> +
> Wmissing-braces
> C ObjC C++ ObjC++ Var(warn_missing_braces) Warning LangEnabledBy(C ObjC,Wall)
> Warn about possibly missing braces around initializers
>
>
> Jakub
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