On Mon, 6 Jun 2022 at 01:39, Miika via Gcc <[email protected]> wrote:
>
> Based on Jakub's and Yair's comments I created a new attribute "inrange".
> Inrage takes three arguments, pos min and max.
> Pos being the argument position in the function, and min and max defines the
> range of valid integer. Both min and max are inclusive and work with enums.
> Warnings are enabled with the new flag: "-Winrange".
>
> The attribute definition would look something like this:
> inrange(pos, min, max)
>
>
> So for example compiling this with "gcc foo.c -Winrange":
>
> #include <stdio.h>
> void foo(int d) __attribute__ ((inrange (1, 100, 200)));
> void foo(int d) {
> printf("%d\n", d == 0);
> }
>
> int main() {
> foo(0); // warning
> foo(100); // no warning
> }
>
> Would give the following error:
>
> foo.c: In function 'main':
> foo.c:8:9: warning: argument in position 1 not in rage of 100..200 [-Winrange]
> 8 | foo(0); // warning
> | ^~~
>
>
> I thought about having separate minval and maxval attributes but I personally
> prefer that min and max values have to be defined explicitly.
>
> If this looks good, I could look into applying inrange to types and variables
> and after that I could start looking into optimization.
>
> Patch for adding inrange is attached below
Hi,
Thanks for the POC patch!
A few suggestions:
(1) It doesn't apply as-is because of transition from .c to .cc filenames.
Perhaps you're using an older version of trunk ?
(2) AFAIK, this warning will need an entry in doc/invoke.texi for
documenting it.
(3) While this patch addresses warning, I suppose it could be extended
so the tree optimizer
can take advantage of value range info provided by the attribute.
For example, the condition d > 20, could be optimized away in
following function by inferring
range from the attribute.
__attribute__((inrange (1, 10, 20)))
void foo(int d)
{
if (d > 20)
__builtin_abort ();
}
>
> Miika
>
> ---
> diff --git a/gcc/builtin-attrs.def b/gcc/builtin-attrs.def
> index 3239311b5a4..2f5732b3ed2 100644
> --- a/gcc/builtin-attrs.def
> +++ b/gcc/builtin-attrs.def
> @@ -98,6 +98,7 @@ DEF_ATTR_IDENT (ATTR_FORMAT, "format")
> DEF_ATTR_IDENT (ATTR_FORMAT_ARG, "format_arg")
> DEF_ATTR_IDENT (ATTR_MALLOC, "malloc")
> DEF_ATTR_IDENT (ATTR_NONNULL, "nonnull")
> +DEF_ATTR_IDENT (ATTR_INRANGE, "inrange")
> DEF_ATTR_IDENT (ATTR_NORETURN, "noreturn")
> DEF_ATTR_IDENT (ATTR_NOTHROW, "nothrow")
> DEF_ATTR_IDENT (ATTR_LEAF, "leaf")
> diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
> index ac936d5bbbb..d6dc9c37723 100644
> --- a/gcc/c-family/c-attribs.c
> +++ b/gcc/c-family/c-attribs.c
> @@ -119,6 +119,7 @@ static tree handle_novops_attribute (tree *, tree, tree,
> int, bool *);
> static tree handle_vector_size_attribute (tree *, tree, tree, int,
> bool *);
> static tree handle_nonnull_attribute (tree *, tree, tree, int, bool *);
> +static tree handle_inrange_attribute (tree *, tree, tree, int, bool *);
> static tree handle_nonstring_attribute (tree *, tree, tree, int, bool *);
> static tree handle_nothrow_attribute (tree *, tree, tree, int, bool *);
> static tree handle_cleanup_attribute (tree *, tree, tree, int, bool *);
> @@ -379,6 +380,8 @@ const struct attribute_spec c_common_attribute_table[] =
> handle_tls_model_attribute, NULL },
> { "nonnull", 0, -1, false, true, true, false,
> handle_nonnull_attribute, NULL },
> + { "inrange", 3, 3, false, true, true, false,
> + handle_inrange_attribute, NULL },
> { "nonstring", 0, 0, true, false, false, false,
> handle_nonstring_attribute, NULL },
> { "nothrow", 0, 0, true, false, false, false,
> @@ -3754,6 +3757,59 @@ handle_nonnull_attribute (tree *node, tree name,
> return NULL_TREE;
> }
>
> +/* Handle the "inrange" attribute. */
> +
> +static tree
> +handle_inrange_attribute (tree *node, tree name,
> + tree args, int ARG_UNUSED (flags),
> + bool *no_add_attrs)
> +{
> + tree type = *node;
> +
> + /* Test the position argument */
> + tree pos = TREE_VALUE (args);
> + if (!positional_argument (type, name, pos, INTEGER_TYPE, 0))
> + *no_add_attrs = true;
> +
> + /* Make sure that range args are INTEGRALs */
> + bool range_err = false;
> + for (tree range = TREE_CHAIN (args); range; range = TREE_CHAIN (range))
> + {
> + tree val = TREE_VALUE (range);
> + if (val && TREE_CODE (val) != IDENTIFIER_NODE
> + && TREE_CODE (val) != FUNCTION_DECL)
> + val = default_conversion (val);
> +
> + if (TREE_CODE (val) != INTEGER_CST
> + || !INTEGRAL_TYPE_P (TREE_TYPE (val)))
Um, why the check for INTEGRAL_TYPE_P here ?
IIUC, this will also accept non-constant integer values.
For eg, the following compiles without any warning:
int a;
int b;
void foo(int d) __attribute__ ((inrange (1, a, b)));
void foo(int d) {
__builtin_printf("%d\n", d == 0);
}
Is this intended ?
> + {
> + warning (OPT_Wattributes,
> + "range value is not an integral constant");
> + *no_add_attrs = true;
> + range_err = true;
> + }
> + }
> +
> + /* Test the range arg max is not smaller than min
> + if range args are integrals */
> + if (!range_err)
> + {
> + tree range = TREE_CHAIN (args);
> + tree min = TREE_VALUE(range);
> + range = TREE_CHAIN (range);
> + tree max = TREE_VALUE(range);
> + if (!tree_int_cst_le (min, max))
> + {
> + warning (OPT_Wattributes,
> + "min range is bigger than max range");
> + *no_add_attrs = true;
> + return NULL_TREE;
> + }
> + }
> +
> + return NULL_TREE;
> +}
> +
> /* Handle the "nonstring" variable attribute. */
>
> static tree
> diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
> index 20258c331af..8936942fec8 100644
> --- a/gcc/c-family/c-common.c
> +++ b/gcc/c-family/c-common.c
> @@ -5342,6 +5342,51 @@ check_function_nonnull (location_t loc, tree attrs,
> int nargs, tree *argarray)
> return ctx.warned_p;
> }
>
> +
> +/* Check the argument list of a function call for invalid range
> + in argument slots that are marked as requiring a specific range.
> + Return true if we have warned. */
> +
> +static bool
> +check_function_inrange (location_t loc, tree attrs, tree *argarray)
> +{
> + tree a;
> + tree param;
> + int pos;
> + HOST_WIDE_INT min;
> + HOST_WIDE_INT max;
> + HOST_WIDE_INT value;
> + bool warned = false;
> +
> + attrs = lookup_attribute ("inrange", attrs);
> + if (attrs == NULL_TREE)
> + return false;
> +
> + /* Walk through attributes and check range values
> + when range attribute is found */
> +
> + for (a = attrs; a ; a = TREE_CHAIN (a))
> + {
> + a = lookup_attribute ("inrange", a);
> + tree op = TREE_VALUE (a);
> + pos = TREE_INT_CST_LOW (TREE_VALUE (op));
> + op = TREE_CHAIN (op);
> + min = tree_to_shwi (TREE_VALUE (op));
> + op = TREE_CHAIN (op);
> + max = tree_to_shwi (TREE_VALUE (op));
> + param = argarray[pos - 1];
> + value = TREE_INT_CST_LOW (param);
> + if (value < min || value > max)
> + {
> + warning_at (loc, OPT_Winrange, "argument in position %u"
> + " not in rage of %ld..%ld", pos, min, max);
> + warned = true;
> + }
> + }
> +
> + return warned;
> +}
> +
> /* Check that the Nth argument of a function call (counting backwards
> from the end) is a (pointer)0. The NARGS arguments are passed in the
> array ARGARRAY. */
> @@ -5703,7 +5748,7 @@ attribute_fallthrough_p (tree attr)
>
> /* Check for valid arguments being passed to a function with FNTYPE.
> There are NARGS arguments in the array ARGARRAY. LOC should be used
> - for diagnostics. Return true if either -Wnonnull or -Wrestrict has
> + for diagnostics. Return true if -Winrange, -Wnonnull or -Wrestrict has
> been issued.
>
> The arguments in ARGARRAY may not have been folded yet (e.g. for C++,
> @@ -5723,6 +5768,10 @@ check_function_arguments (location_t loc, const_tree
> fndecl, const_tree fntype,
> warned_p = check_function_nonnull (loc, TYPE_ATTRIBUTES (fntype),
> nargs, argarray);
>
> + if (warn_inrange)
> + warned_p = check_function_inrange (loc, TYPE_ATTRIBUTES (fntype),
> + argarray);
> +
> /* Check for errors in format strings. */
>
> if (warn_format || warn_suggest_attribute_format)
> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> index c49da99d395..0b9aa597c54 100644
> --- a/gcc/c-family/c.opt
> +++ b/gcc/c-family/c.opt
> @@ -932,6 +932,14 @@ Wnonnull-compare
> C ObjC C++ ObjC++ LangEnabledBy(C ObjC C++ ObjC++,Wall)
> ;
>
> +Winrange
> +C Var(warn_inrange) Warning LangEnabledBy(C,Wformat=,warn_format >= 1,0)
> +Warn about integer not being in specified range.
> +
> +Winrange
> +C LangEnabledBy(C,Wall)
Just curious, why only C ?
Thanks,
Prathamesh
> +;
> +
> Wnormalized
> C ObjC C++ ObjC++ Warning Alias(Wnormalized=,nfc,none)
> ;
>
>
>
