From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ej1-x62f.google.com (mail-ej1-x62f.google.com [IPv6:2a00:1450:4864:20::62f]) by sourceware.org (Postfix) with ESMTPS id 9AE8A386C5BD for ; Sun, 12 Jun 2022 04:25:59 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 9AE8A386C5BD Received: by mail-ej1-x62f.google.com with SMTP id u12so5127285eja.8 for ; Sat, 11 Jun 2022 21:25:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=yx3Xon5GYJjDG0QiRLcCSlDbZ0AQZmGT+3lYCw+ob0Y=; b=GqUteUqgAlSlSOSW20U5e4vgG78abaTWVDjql1zAN8xGK2Fe/DoePC+BFl+a8TslEC N/5s9k9QoWDOU7yvIHlYqCqR8qo2UT1qxxpw/G3TxZ3NlC8YNFdF5uFv73mC74U/8q0T WW1KbtYqLiTLnO9wjl1QEyfaxiiSG7wNj0pEFBF1KMMN1/4IECeQPHj0S6wpAyKNehNT Wq0HP7M6OwV9q1su8mvsN0Q7cOdG1fZHvc/OPqFJG+1O6dYZQHUaYjVhkq5VzbJeBBGL HIP7e7tDv27FXbU/8HlOzeYN14HdOtBa3L21y7I8PINU/jI6KqAEUNRBs5CZmDoqJvzz g4aQ== X-Gm-Message-State: AOAM531Q041e/+2NvuKQv7mGix1hqsLZ1h1W9lSbSGR2FrZ9odZhocXk 66hXSzdpudwPC+2E6eJY/yUgJfAJ9iBCCoKuLthmag== X-Google-Smtp-Source: ABdhPJyU7KyMqTsMLQgI38WYozoV3FKXrTalKQBcnXCho1ZsYBS5+cmdqEu2mb90OVZtz6ugf6eahx2YHYqHsJidl3E= X-Received: by 2002:a17:907:6e13:b0:711:c722:4fc with SMTP id sd19-20020a1709076e1300b00711c72204fcmr33200144ejc.253.1655007958247; Sat, 11 Jun 2022 21:25:58 -0700 (PDT) MIME-Version: 1.0 References: <6PeOfngSW_gLKMPtqp7UWs9ZQRv6KpLer221P_B9lNGGC7nJD0p-ta_7b0fwgSdz6cw7UzXsO0OGg0t2UUux81cVfIZkQcbjPwcRHFsNomI=@protonmail.com> In-Reply-To: <6PeOfngSW_gLKMPtqp7UWs9ZQRv6KpLer221P_B9lNGGC7nJD0p-ta_7b0fwgSdz6cw7UzXsO0OGg0t2UUux81cVfIZkQcbjPwcRHFsNomI=@protonmail.com> From: Prathamesh Kulkarni Date: Sun, 12 Jun 2022 09:55:24 +0530 Message-ID: Subject: Re: [RFC] Support for nonzero attribute To: Miika Cc: "gcc@gcc.gnu.org" Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-9.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 12 Jun 2022 04:26:02 -0000 On Mon, 6 Jun 2022 at 01:39, Miika via Gcc 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 > 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) > ; > > >