From nobody Mon Mar 20 19:14:25 2023 X-Original-To: dtrace@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4PgPYY2mv1z4078C for ; Mon, 20 Mar 2023 19:14:25 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4PgPYY0BMNz4Ytl for ; Mon, 20 Mar 2023 19:14:25 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1679339665; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=idFDarW5gB0fUmleZCtmmStYAuw9Hr4I0rqaTsh//mk=; b=J2XyH2VBx6PvuATNDpcbNokHDohqfUGwWsT0GPCaT4VxkfmTix3NXNCmgoVexHcx1QVXxn z5axqTDwP9ne7Gh3gniRPCghuqFjSvfr7cJhtWG28s3PgIzFZ+DMcB/Pnyuk+HMVUon1b7 EeWwH5WG6kA65Y8wJ5r4MCcFQxdDlRUYRorf3rCkZ78+gWXem7g1joc8hCCHnRoxts8J74 ZyW1JepVlsf59EZgTfLkQczQWWdsag8ttjD+RZaq1vuYAojtuOge6RVLyB5cpqBF5zzASx 3vQajUL2pGtwMJnklR5mKc7cpPrVXwj8UyjmV7dHCVSZcc36W3/5nX6OnPf5cg== ARC-Authentication-Results: i=1; mx1.freebsd.org; none ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1679339665; a=rsa-sha256; cv=none; b=CazN2QCOfPCBHpXwbH4zFkYn+4Z6IFn5nSGBpFDc4W9qTMSOm9ouG3xA7qon9hm4GnPfea jl46VsTvI2OSHKW4vqGLLyB/HxeL0Qg+YCkykJ6rHzWzH1194qXW6uHEZirVvOV/nuuwsT RlCuFZ5oPVl4Jaf+Y0j5vXxrtLbFV6CumWknf0DSgn4B47GiUAHfVxM4Y/OOHA1AL47fsy ST8TzYLFNJG9l77osK31IOtyhEV29DOs1bj2c9pvK2wH70HiA96FT1VY9OYD/zH2w7owDv oXPlsKdNu/YMGXP7MnjGWtIR8WAPv/gG8vQZkuUTrmtx8p5G50g7t1RmxlDwuQ== Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2610:1c1:1:606c::50:1d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4PgPYX6PT9zhjj for ; Mon, 20 Mar 2023 19:14:24 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.5]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id 32KJEOTf087037 for ; Mon, 20 Mar 2023 19:14:24 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 32KJEO15087036 for dtrace@FreeBSD.org; Mon, 20 Mar 2023 19:14:24 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: dtrace@FreeBSD.org Subject: [Bug 269906] dtrace requires empty expression to print anything from matching search Date: Mon, 20 Mar 2023 19:14:25 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: CURRENT X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: christos@margiolis.net X-Bugzilla-Status: Closed X-Bugzilla-Resolution: Overcome By Events X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: dtrace@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated List-Id: A discussion list for developers working on DTrace in FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-dtrace List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-dtrace@freebsd.org MIME-Version: 1.0 X-ThisMailContainsUnwantedMimeParts: N https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D269906 --- Comment #5 from Christos Margiolis --- Apparently, this patch doesn't really work and, in fact, allowing a predica= te with no acts is probably impossible in D without introducing a significant amount of complexity. awk can do that just fine because awk's predicates ca= nnot contain unescaped "/", since it searches for regexes. D on the other hand allows normal computation inside the predicate, meaning one can do division inside it: kinst::vm_fault: /(cpu / 2) =3D=3D 1/ This is a problem because the D lexer considers "/" to be a division token = (and not a start/end of predicate token) when the next non-whitespace character coming after it is anything other than EOF, 0, ;, { and }, so if we try and run: kinst::vm_fault: /cpu =3D=3D 1/ fbt::malloc:entry The lexer will think the end of predicate is actually a division token beca= use the succeeding non-whitespace character "f" doesn't match the character set that indicate the end of predicate. --=20 You are receiving this mail because: You are the assignee for the bug.=