From mboxrd@z Thu Jan 1 00:00:00 1970 From: Luc Van Oostenryck Subject: [PATCH 3/9] div0: warn on integer divide by 0 also when the lhs is not constant Date: Wed, 31 May 2017 05:22:01 +0200 Message-ID: <20170531032207.95830-4-luc.vanoostenryck@gmail.com> References: <20170531032207.95830-1-luc.vanoostenryck@gmail.com> Return-path: Received: from mail-wr0-f193.google.com ([209.85.128.193]:34785 "EHLO mail-wr0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751090AbdEaDWU (ORCPT ); Tue, 30 May 2017 23:22:20 -0400 Received: by mail-wr0-f193.google.com with SMTP id 6so305283wrb.1 for ; Tue, 30 May 2017 20:22:19 -0700 (PDT) In-Reply-To: <20170531032207.95830-1-luc.vanoostenryck@gmail.com> Sender: linux-sparse-owner@vger.kernel.org List-Id: linux-sparse@vger.kernel.org To: linux-sparse@vger.kernel.org Cc: Luc Van Oostenryck The current code detects and warns on division by zero but only when the left-hand side is a constant value. Fix that by moving up the code which detect such divisions before checking if the LHS is a constant. Signed-off-by: Luc Van Oostenryck --- expand.c | 8 ++------ validation/div-by-zero.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+), 6 deletions(-) create mode 100644 validation/div-by-zero.c diff --git a/expand.c b/expand.c index 5f908c971..0b528ea5a 100644 --- a/expand.c +++ b/expand.c @@ -181,6 +181,8 @@ static int simplify_int_binop(struct expression *expr, struct symbol *ctype) if (right->type != EXPR_VALUE) return 0; r = right->value; + if (!r && (expr->op == '/' || expr->op == '%')) + goto Div; if (expr->op == SPECIAL_LEFTSHIFT || expr->op == SPECIAL_RIGHTSHIFT) { if (r >= ctype->bit_size) { if (conservative) @@ -235,28 +237,22 @@ static int simplify_int_binop(struct expression *expr, struct symbol *ctype) break; case SIGNED('/'): - if (!r) - goto Div; if (l == mask && sr == -1) goto Overflow; v = sl / sr; break; case UNSIGNED('/'): - if (!r) goto Div; v = l / r; break; case SIGNED('%'): - if (!r) - goto Div; if (l == mask && sr == -1) goto Overflow; v = sl % sr; break; case UNSIGNED('%'): - if (!r) goto Div; v = l % r; break; diff --git a/validation/div-by-zero.c b/validation/div-by-zero.c new file mode 100644 index 000000000..786e48298 --- /dev/null +++ b/validation/div-by-zero.c @@ -0,0 +1,43 @@ +int scdiv(int a) { return 2 / 0; } +int iscdiv(int a) { return 2 / (int) 0; } +int lscdiv(int a) { return 2 / (long) 0; } +int uscdiv(int a) { return 2 / (unsigned int) 0; } + +int svdiv(int a) { return a / 0; } +int isvdiv(int a) { return a / (int) 0; } +int lsvdiv(int a) { return a / (long) 0; } +int usvdiv(int a) { return a / (unsigned int) 0; } + +int scmod(int a) { return 2 % 0; } +int iscmod(int a) { return 2 % (int) 0; } +int lscmod(int a) { return 2 % (long) 0; } +int uscmod(int a) { return 2 % (unsigned int) 0; } + +int svmod(int a) { return a % 0; } +int isvmod(int a) { return a % (int) 0; } +int lsvmod(int a) { return a % (long) 0; } +int usvmod(int a) { return a % (unsigned int) 0; } + +/* + * check-name: div-by-zero.c + * check-command: sparse -Wno-decl $file + * + * check-error-start +div-by-zero.c:1:30: warning: division by zero +div-by-zero.c:2:30: warning: division by zero +div-by-zero.c:3:30: warning: division by zero +div-by-zero.c:4:30: warning: division by zero +div-by-zero.c:6:30: warning: division by zero +div-by-zero.c:7:30: warning: division by zero +div-by-zero.c:8:30: warning: division by zero +div-by-zero.c:9:30: warning: division by zero +div-by-zero.c:11:30: warning: division by zero +div-by-zero.c:12:30: warning: division by zero +div-by-zero.c:13:30: warning: division by zero +div-by-zero.c:14:30: warning: division by zero +div-by-zero.c:16:30: warning: division by zero +div-by-zero.c:17:30: warning: division by zero +div-by-zero.c:18:30: warning: division by zero +div-by-zero.c:19:30: warning: division by zero + * check-error-end + */ -- 2.13.0