{"id":10988,"url":"https://patchwork.libcamera.org/api/patches/10988/?format=json","web_url":"https://patchwork.libcamera.org/patch/10988/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/projects/1/?format=json","name":"libcamera","link_name":"libcamera","list_id":"libcamera_core","list_email":"libcamera-devel@lists.libcamera.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20210125172210.31681-1-laurent.pinchart@ideasonboard.com>","date":"2021-01-25T17:22:10","name":"[libcamera-devel,PATCH/RFC] libcamera: geometry: Mark const functions with [[nodiscard]]","commit_ref":null,"pull_url":null,"state":"rfc","archived":false,"hash":"e06279a41dffaefae740686248e25f88bee2fe87","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/?format=json","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"delegate":{"id":14,"url":"https://patchwork.libcamera.org/api/users/14/?format=json","username":"pinchartl","first_name":"Laurent","last_name":"Pinchart","email":"laurent.pinchart@ideasonboard.com"},"mbox":"https://patchwork.libcamera.org/patch/10988/mbox/","series":[{"id":1605,"url":"https://patchwork.libcamera.org/api/series/1605/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=1605","date":"2021-01-25T17:22:10","name":"[libcamera-devel,PATCH/RFC] libcamera: geometry: Mark const functions with [[nodiscard]]","version":1,"mbox":"https://patchwork.libcamera.org/series/1605/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/10988/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/10988/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 1D0A1BD808\n\tfor ;\n\tMon, 25 Jan 2021 17:22:35 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 8A937682D2;\n\tMon, 25 Jan 2021 18:22:34 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 44D5D682CB\n\tfor ;\n\tMon, 25 Jan 2021 18:22:33 +0100 (CET)","from pendragon.lan (62-78-145-57.bb.dnainternet.fi [62.78.145.57])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id AB9B0331\n\tfor ;\n\tMon, 25 Jan 2021 18:22:32 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"GIk0LEhN\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1611595352;\n\tbh=+Qmrh31NsxTa8X3jWsgKQtfszaUOz8sDR4FfvAlCTys=;\n\th=From:To:Subject:Date:From;\n\tb=GIk0LEhN1iPtrCR9pEGRCKpzeveZBwN2dH7ExtQRoAOicCTT72rWZ4CJlLanysUWd\n\tdGNRYOPZd16H2L7sspGJRCxOghVpT/8c7FCNM0bLmrP8quq5bqQUUZPTM2mkuALdr0\n\t04QXsnfuqkNWyyPjhKRtoYniEvgQl9nXhodLyU8I=","From":"Laurent Pinchart ","To":"libcamera-devel@lists.libcamera.org","Date":"Mon, 25 Jan 2021 19:22:10 +0200","Message-Id":"<20210125172210.31681-1-laurent.pinchart@ideasonboard.com>","X-Mailer":"git-send-email 2.28.0","MIME-Version":"1.0","Subject":"[libcamera-devel] [PATCH/RFC] libcamera: geometry: Mark const\n\tfunctions with [[nodiscard]]","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "},"content":"Geometry classes generally have two sets of functions, one that operates\non the object and modifies it (e.g. Rectangle::scaleBy()), and one that\nperforms the same operations by instead return a modified copy of the\nobject, leaving the original untouched (e.g.Rectangle::scaledBy()). As\nthe names are close, they can easily be mistaken, with the const version\nused instead of the in-place version.\n\nTo catch these errors at compile time, mark the const versions with\n[[nodiscard]], as there is no use case for calling them without using\nthe result of the call.\n\nSigned-off-by: Laurent Pinchart \n---\n include/libcamera/geometry.h | 27 ++++++++++++++-------------\n 1 file changed, 14 insertions(+), 13 deletions(-)\n\nThis patch came as a result of catching one of the issues described in\nthe commit message during review of another patch. [[nodiscard]] is only\navailable in C++17, which would make it impossible to use libcamera in\nC++14 code (this can for instance for a problem with Chromium - the web\nbrowser, not the OS). An alternative would be to define a custom\nattribute, for instance\n\n#define __nodiscard [[nodiscard]]\n\nin a public header (compile.h ? util.h ?), conditionally on the C++\nversion. The check would thus be disabled in application compiled with\nC++14, but would be enabled for the compilation of libcamera itself.\n\nIs this worth it ?","diff":"diff --git a/include/libcamera/geometry.h b/include/libcamera/geometry.h\nindex 2f3a82e2afc3..0a9d61f45874 100644\n--- a/include/libcamera/geometry.h\n+++ b/include/libcamera/geometry.h\n@@ -92,8 +92,8 @@ public:\n \t\treturn *this;\n \t}\n \n-\tconstexpr Size alignedDownTo(unsigned int hAlignment,\n-\t\t\t\t unsigned int vAlignment) const\n+\t[[nodiscard]] constexpr Size alignedDownTo(unsigned int hAlignment,\n+\t\t\t\t\t\t unsigned int vAlignment) const\n \t{\n \t\treturn {\n \t\t\twidth / hAlignment * hAlignment,\n@@ -101,8 +101,8 @@ public:\n \t\t};\n \t}\n \n-\tconstexpr Size alignedUpTo(unsigned int hAlignment,\n-\t\t\t\t unsigned int vAlignment) const\n+\t[[nodiscard]] constexpr Size alignedUpTo(unsigned int hAlignment,\n+\t\t\t\t\t\t unsigned int vAlignment) const\n \t{\n \t\treturn {\n \t\t\t(width + hAlignment - 1) / hAlignment * hAlignment,\n@@ -110,7 +110,7 @@ public:\n \t\t};\n \t}\n \n-\tconstexpr Size boundedTo(const Size &bound) const\n+\t[[nodiscard]] constexpr Size boundedTo(const Size &bound) const\n \t{\n \t\treturn {\n \t\t\tstd::min(width, bound.width),\n@@ -118,7 +118,7 @@ public:\n \t\t};\n \t}\n \n-\tconstexpr Size expandedTo(const Size &expand) const\n+\t[[nodiscard]] constexpr Size expandedTo(const Size &expand) const\n \t{\n \t\treturn {\n \t\t\tstd::max(width, expand.width),\n@@ -126,10 +126,10 @@ public:\n \t\t};\n \t}\n \n-\tSize boundedToAspectRatio(const Size &ratio) const;\n-\tSize expandedToAspectRatio(const Size &ratio) const;\n+\t[[nodiscard]] Size boundedToAspectRatio(const Size &ratio) const;\n+\t[[nodiscard]] Size expandedToAspectRatio(const Size &ratio) const;\n \n-\tRectangle centeredTo(const Point ¢er) const;\n+\t[[nodiscard]] Rectangle centeredTo(const Point ¢er) const;\n \n \tSize operator*(float factor) const;\n \tSize operator/(float factor) const;\n@@ -247,10 +247,11 @@ public:\n \tRectangle &scaleBy(const Size &numerator, const Size &denominator);\n \tRectangle &translateBy(const Point &point);\n \n-\tRectangle boundedTo(const Rectangle &bound) const;\n-\tRectangle enclosedIn(const Rectangle &boundary) const;\n-\tRectangle scaledBy(const Size &numerator, const Size &denominator) const;\n-\tRectangle translatedBy(const Point &point) const;\n+\t[[nodiscard]] Rectangle boundedTo(const Rectangle &bound) const;\n+\t[[nodiscard]] Rectangle enclosedIn(const Rectangle &boundary) const;\n+\t[[nodiscard]] Rectangle scaledBy(const Size &numerator,\n+\t\t\t\t\t const Size &denominator) const;\n+\t[[nodiscard]] Rectangle translatedBy(const Point &point) const;\n };\n \n bool operator==(const Rectangle &lhs, const Rectangle &rhs);\n","prefixes":["libcamera-devel","PATCH/RFC"]}