[{"id":12113,"web_url":"https://patchwork.libcamera.org/comment/12113/","msgid":"<64ba9b42-9ee0-e40f-6b5c-f749d74a4cb6@ideasonboard.com>","date":"2020-08-24T09:52:53","subject":"Re: [libcamera-devel] [PATCH v1.1 1/5] meson: Switch to C++17","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"On 22/08/2020 21:04, Laurent Pinchart wrote:\n> Due to popular request, move from C++14 to C++17. This will allow\n> dropping some custom constructs (such as a custom utils::clamp),\n> benefiting from new language features, and dropping gcc 5 and 6 from the\n> compilation tests.\n> \n> Signed-off-by: Laurent Pinchart \n> ---\n> Changes since v1:\n> \n> - Update documentation\n> - Print an error message when detecting a too old compiler\n\nOk, some useful additions... reading. ..\n\n\n> ---\n> Documentation/coding-style.rst | 5 ++---\n> meson.build | 29 ++++++++++++++++++-----------\n> 2 files changed, 20 insertions(+), 14 deletions(-)\n> \n> diff --git a/Documentation/coding-style.rst b/Documentation/coding-style.rst\n> index 7acba37b8de8..7c56a1b70014 100644\n> --- a/Documentation/coding-style.rst\n> +++ b/Documentation/coding-style.rst\n> @@ -88,13 +88,12 @@ headers, and with double quotes for other libcamera headers.\n> C++ Specific Rules\n> ------------------\n> \n> -The code shall be implemented in C++14, with the following caveats:\n> +The code shall be implemented in C++17, with the following caveats:\n> \n> * Type inference (auto and decltype) shall be used with caution, to avoid\n> drifting towards an untyped language.\n> * The explicit, override and final specifiers are to be used where applicable.\n> -* General-purpose smart pointers (std::unique_ptr) deprecate std::auto_ptr.\n> - Smart pointers, as well as shared pointers and weak pointers, shall not be\n> +* Smart pointers, as well as shared pointers and weak pointers, shall not be\n> overused.\n> * Classes are encouraged to define move constructors and assignment operators\n> where applicable, and generally make use of the features offered by rvalue\n> diff --git a/meson.build b/meson.build\n> index ec54e68f3635..cf2636d97100 100644\n> --- a/meson.build\n> +++ b/meson.build\n> @@ -6,7 +6,7 @@ project('libcamera', 'c', 'cpp',\n> default_options : [\n> 'werror=true',\n> 'warning_level=2',\n> - 'cpp_std=c++14',\n> + 'cpp_std=c++17',\n> ],\n> license : 'LGPL 2.1+')\n> \n> @@ -62,6 +62,23 @@ if cc.get_id() == 'clang'\n> endif\n> endif\n> \n> +if cc.get_id() == 'gcc'\n> + if cc.version().version_compare('<7')\n> + error('gcc version is too old, libcamera requires 7.0 or newer')\n> + endif\n\n\nClang v5 or greater is required for C++17. Do we need to catch that too?\nor is that considered old enough that we're not going to hit it.\n\nI think it looks like Clang 5 was released around September 2017, while\nGCC 7.1 was released earlier in May 2017.\n\nThat said, wouldn't the compiler warn us quite verbosely if it didn't\nsupport C++17 ?\n\nI.e. .. do /we/ really need to do this check here in meson?\n\nAnyway,\n\nReviewed-by: Kieran Bingham \n\nStill stands.\n\n\n> +\n> + # gcc 7.1 introduced processor-specific ABI breakages related to parameter\n> + # passing on ARM platforms. This generates a large number of messages\n> + # during compilation with gcc >=7.1 until gcc 9. Silence them.\n> + if (host_machine.cpu_family() == 'arm' and\n> + cc.version().version_compare('>=7.1') and\n> + cc.version().version_compare('<9'))\n> + cpp_arguments += [\n> + '-Wno-psabi',\n> + ]\n> + endif\n> +endif\n> +\n> # We use C99 designated initializers for arrays as C++ has no equivalent\n> # feature. Both gcc and clang support this extension, but recent\n> # versions of clang generate a warning that needs to be disabled.\n> @@ -71,16 +88,6 @@ if cc.has_argument('-Wno-c99-designator')\n> ]\n> endif\n> \n> -# gcc 7.1 introduced processor-specific ABI breakages related to parameter\n> -# passing on ARM platforms. This generates a large number of messages during\n> -# compilation with gcc >=7.1 until gcc 9. Silence them.\n> -if (host_machine.cpu_family() == 'arm' and cc.get_id() == 'gcc' and\n> - cc.version().version_compare('>=7.1') and cc.version().version_compare('<9'))\n> - cpp_arguments += [\n> - '-Wno-psabi',\n> - ]\n> -endif\n> -\n> c_arguments += common_arguments\n> cpp_arguments += common_arguments\n> \n>","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 184F3BE173\n\tfor ;\n\tMon, 24 Aug 2020 09:53:00 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 897D062818;\n\tMon, 24 Aug 2020 11:52:59 +0200 (CEST)","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 A0A0460387\n\tfor ;\n\tMon, 24 Aug 2020 11:52:58 +0200 (CEST)","from [192.168.0.20]\n\t(cpc89244-aztw30-2-0-cust3082.18-1.cable.virginm.net [86.31.172.11])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id E0289279;\n\tMon, 24 Aug 2020 11:52:55 +0200 (CEST)"],"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=\"hKl0f0SC\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1598262776;\n\tbh=8TqLKMY2s7j1gPs2Xli1ghwreoXBmaSuP4IYToHklPc=;\n\th=Reply-To:Subject:To:References:From:Date:In-Reply-To:From;\n\tb=hKl0f0SCEiEDJEDx7Pr7uBSyiv502RTWUOEuPWVmwi565js71kMT1E57Hj1HCzjUM\n\tFITenYWKvLGbXhjEbRs4pA3eZvXf/pUkfH5fgLunVEGUQ1+Zt2n3RNx8vl2+/zjgfc\n\tyP5UI5sMBHnGRigHgHMNM9jYR+PjYQ4AxKjVUAwA=","To":"Laurent Pinchart ,\n\tlibcamera-devel@lists.libcamera.org","References":"<20200822200037.20892-2-laurent.pinchart@ideasonboard.com>\n\t<20200822200454.21718-1-laurent.pinchart@ideasonboard.com>","From":"Kieran Bingham ","Autocrypt":"addr=kieran.bingham@ideasonboard.com; keydata=\n\tmQINBFYE/WYBEACs1PwjMD9rgCu1hlIiUA1AXR4rv2v+BCLUq//vrX5S5bjzxKAryRf0uHat\n\tV/zwz6hiDrZuHUACDB7X8OaQcwhLaVlq6byfoBr25+hbZG7G3+5EUl9cQ7dQEdvNj6V6y/SC\n\trRanWfelwQThCHckbobWiQJfK9n7rYNcPMq9B8e9F020LFH7Kj6YmO95ewJGgLm+idg1Kb3C\n\tpotzWkXc1xmPzcQ1fvQMOfMwdS+4SNw4rY9f07Xb2K99rjMwZVDgESKIzhsDB5GY465sCsiQ\n\tcSAZRxqE49RTBq2+EQsbrQpIc8XiffAB8qexh5/QPzCmR4kJgCGeHIXBtgRj+nIkCJPZvZtf\n\tKr2EAbc6tgg6DkAEHJb+1okosV09+0+TXywYvtEop/WUOWQ+zo+Y/OBd+8Ptgt1pDRyOBzL8\n\tRXa8ZqRf0Mwg75D+dKntZeJHzPRJyrlfQokngAAs4PaFt6UfS+ypMAF37T6CeDArQC41V3ko\n\tlPn1yMsVD0p+6i3DPvA/GPIksDC4owjnzVX9kM8Zc5Cx+XoAN0w5Eqo4t6qEVbuettxx55gq\n\t8K8FieAjgjMSxngo/HST8TpFeqI5nVeq0/lqtBRQKumuIqDg+Bkr4L1V/PSB6XgQcOdhtd36\n\tOe9X9dXB8YSNt7VjOcO7BTmFn/Z8r92mSAfHXpb07YJWJosQOQARAQABtDBLaWVyYW4gQmlu\n\tZ2hhbSA8a2llcmFuLmJpbmdoYW1AaWRlYXNvbmJvYXJkLmNvbT6JAlcEEwEKAEECGwMFCwkI\n\tBwIGFQgJCgsCBBYCAwECHgECF4ACGQEWIQSQLdeYP70o/eNy1HqhHkZyEKRh/QUCXWTtygUJ\n\tCyJXZAAKCRChHkZyEKRh/f8dEACTDsbLN2nioNZMwyLuQRUAFcXNolDX48xcUXsWS2QjxaPm\n\tVsJx8Uy8aYkS85mdPBh0C83OovQR/OVbr8AxhGvYqBs3nQvbWuTl/+4od7DfK2VZOoKBAu5S\n\tQK2FYuUcikDqYcFWJ8DQnubxfE8dvzojHEkXw0sA4igINHDDFX3HJGZtLio+WpEFQtCbfTAG\n\tYZslasz1YZRbwEdSsmO3/kqy5eMnczlm8a21A3fKUo3g8oAZEFM+f4DUNzqIltg31OAB/kZS\n\tenKZQ/SWC8PmLg/ZXBrReYakxXtkP6w3FwMlzOlhGxqhIRNiAJfXJBaRhuUWzPOpEDE9q5YJ\n\tBmqQL2WJm1VSNNVxbXJHpaWMH1sA2R00vmvRrPXGwyIO0IPYeUYQa3gsy6k+En/aMQJd27dp\n\taScf9am9PFICPY5T4ppneeJLif2lyLojo0mcHOV+uyrds9XkLpp14GfTkeKPdPMrLLTsHRfH\n\tfA4I4OBpRrEPiGIZB/0im98MkGY/Mu6qxeZmYLCcgD6qz4idOvfgVOrNh+aA8HzIVR+RMW8H\n\tQGBN9f0E3kfwxuhl3omo6V7lDw8XOdmuWZNC9zPq1UfryVHANYbLGz9KJ4Aw6M+OgBC2JpkD\n\thXMdHUkC+d20dwXrwHTlrJi1YNp6rBc+xald3wsUPOZ5z8moTHUX/uPA/qhGsbkCDQRWBP1m\n\tARAAzijkb+Sau4hAncr1JjOY+KyFEdUNxRy+hqTJdJfaYihxyaj0Ee0P0zEi35CbE6lgU0Uz\n\ttih9fiUbSV3wfsWqg1Ut3/5rTKu7kLFp15kF7eqvV4uezXRD3Qu4yjv/rMmEJbbD4cTvGCYI\n\td6MDC417f7vK3hCbCVIZSp3GXxyC1LU+UQr3fFcOyCwmP9vDUR9JV0BSqHHxRDdpUXE26Dk6\n\tmhf0V1YkspE5St814ETXpEus2urZE5yJIUROlWPIL+hm3NEWfAP06vsQUyLvr/GtbOT79vXl\n\tEn1aulcYyu20dRRxhkQ6iILaURcxIAVJJKPi8dsoMnS8pB0QW12AHWuirPF0g6DiuUfPmrA5\n\tPKe56IGlpkjc8cO51lIxHkWTpCMWigRdPDexKX+Sb+W9QWK/0JjIc4t3KBaiG8O4yRX8ml2R\n\t+rxfAVKM6V769P/hWoRGdgUMgYHFpHGSgEt80OKK5HeUPy2cngDUXzwrqiM5Sz6Od0qw5pCk\n\tNlXqI0W/who0iSVM+8+RmyY0OEkxEcci7rRLsGnM15B5PjLJjh1f2ULYkv8s4SnDwMZ/kE04\n\t/UqCMK/KnX8pwXEMCjz0h6qWNpGwJ0/tYIgQJZh6bqkvBrDogAvuhf60Sogw+mH8b+PBlx1L\n\toeTK396wc+4c3BfiC6pNtUS5GpsPMMjYMk7kVvEAEQEAAYkCPAQYAQoAJgIbDBYhBJAt15g/\n\tvSj943LUeqEeRnIQpGH9BQJdizzIBQkLSKZiAAoJEKEeRnIQpGH9eYgQAJpjaWNgqNOnMTmD\n\tMJggbwjIotypzIXfhHNCeTkG7+qCDlSaBPclcPGYrTwCt0YWPU2TgGgJrVhYT20ierN8LUvj\n\t6qOPTd+Uk7NFzL65qkh80ZKNBFddx1AabQpSVQKbdcLb8OFs85kuSvFdgqZwgxA1vl4TFhNz\n\tPZ79NAmXLackAx3sOVFhk4WQaKRshCB7cSl+RIng5S/ThOBlwNlcKG7j7W2MC06BlTbdEkUp\n\tECzuuRBv8wX4OQl+hbWbB/VKIx5HKlLu1eypen/5lNVzSqMMIYkkZcjV2SWQyUGxSwq0O/sx\n\tS0A8/atCHUXOboUsn54qdxrVDaK+6jIAuo8JiRWctP16KjzUM7MO0/+4zllM8EY57rXrj48j\n\tsbEYX0YQnzaj+jO6kJtoZsIaYR7rMMq9aUAjyiaEZpmP1qF/2sYenDx0Fg2BSlLvLvXM0vU8\n\tpQk3kgDu7kb/7PRYrZvBsr21EIQoIjXbZxDz/o7z95frkP71EaICttZ6k9q5oxxA5WC6sTXc\n\tMW8zs8avFNuA9VpXt0YupJd2ijtZy2mpZNG02fFVXhIn4G807G7+9mhuC4XG5rKlBBUXTvPU\n\tAfYnB4JBDLmLzBFavQfvonSfbitgXwCG3vS+9HEwAjU30Bar1PEOmIbiAoMzuKeRm2LVpmq4\n\tWZw01QYHU/GUV/zHJSFk","Organization":"Ideas on Board","Message-ID":"<64ba9b42-9ee0-e40f-6b5c-f749d74a4cb6@ideasonboard.com>","Date":"Mon, 24 Aug 2020 10:52:53 +0100","User-Agent":"Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101\n\tThunderbird/68.10.0","MIME-Version":"1.0","In-Reply-To":"<20200822200454.21718-1-laurent.pinchart@ideasonboard.com>","Content-Language":"en-GB","Subject":"Re: [libcamera-devel] [PATCH v1.1 1/5] meson: Switch to C++17","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","Reply-To":"kieran.bingham@ideasonboard.com","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":12122,"web_url":"https://patchwork.libcamera.org/comment/12122/","msgid":"<20200824175724.GI6002@pendragon.ideasonboard.com>","date":"2020-08-24T17:57:24","subject":"Re: [libcamera-devel] [PATCH v1.1 1/5] meson: Switch to C++17","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Kieran,\n\nOn Mon, Aug 24, 2020 at 10:52:53AM +0100, Kieran Bingham wrote:\n> On 22/08/2020 21:04, Laurent Pinchart wrote:\n> > Due to popular request, move from C++14 to C++17. This will allow\n> > dropping some custom constructs (such as a custom utils::clamp),\n> > benefiting from new language features, and dropping gcc 5 and 6 from the\n> > compilation tests.\n> > \n> > Signed-off-by: Laurent Pinchart \n> > ---\n> > Changes since v1:\n> > \n> > - Update documentation\n> > - Print an error message when detecting a too old compiler\n> \n> Ok, some useful additions... reading. ..\n> \n> > ---\n> > Documentation/coding-style.rst | 5 ++---\n> > meson.build | 29 ++++++++++++++++++-----------\n> > 2 files changed, 20 insertions(+), 14 deletions(-)\n> > \n> > diff --git a/Documentation/coding-style.rst b/Documentation/coding-style.rst\n> > index 7acba37b8de8..7c56a1b70014 100644\n> > --- a/Documentation/coding-style.rst\n> > +++ b/Documentation/coding-style.rst\n> > @@ -88,13 +88,12 @@ headers, and with double quotes for other libcamera headers.\n> > C++ Specific Rules\n> > ------------------\n> > \n> > -The code shall be implemented in C++14, with the following caveats:\n> > +The code shall be implemented in C++17, with the following caveats:\n> > \n> > * Type inference (auto and decltype) shall be used with caution, to avoid\n> > drifting towards an untyped language.\n> > * The explicit, override and final specifiers are to be used where applicable.\n> > -* General-purpose smart pointers (std::unique_ptr) deprecate std::auto_ptr.\n> > - Smart pointers, as well as shared pointers and weak pointers, shall not be\n> > +* Smart pointers, as well as shared pointers and weak pointers, shall not be\n> > overused.\n> > * Classes are encouraged to define move constructors and assignment operators\n> > where applicable, and generally make use of the features offered by rvalue\n> > diff --git a/meson.build b/meson.build\n> > index ec54e68f3635..cf2636d97100 100644\n> > --- a/meson.build\n> > +++ b/meson.build\n> > @@ -6,7 +6,7 @@ project('libcamera', 'c', 'cpp',\n> > default_options : [\n> > 'werror=true',\n> > 'warning_level=2',\n> > - 'cpp_std=c++14',\n> > + 'cpp_std=c++17',\n> > ],\n> > license : 'LGPL 2.1+')\n> > \n> > @@ -62,6 +62,23 @@ if cc.get_id() == 'clang'\n> > endif\n> > endif\n> > \n> > +if cc.get_id() == 'gcc'\n> > + if cc.version().version_compare('<7')\n> > + error('gcc version is too old, libcamera requires 7.0 or newer')\n> > + endif\n> \n> Clang v5 or greater is required for C++17. Do we need to catch that too?\n> or is that considered old enough that we're not going to hit it.\n\nThe lowest clang version installed on my system is 6.0, so I haven't\nconsidered this. It's a good point, I'll add a check.\n\n> I think it looks like Clang 5 was released around September 2017, while\n> GCC 7.1 was released earlier in May 2017.\n> \n> That said, wouldn't the compiler warn us quite verbosely if it didn't\n> support C++17 ?\n> \n> I.e. .. do /we/ really need to do this check here in meson?\n\nHere's how the compiler warns me on gcc 5:\n\n[4/281] Compiling C++ object 'src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o'\nFAILED: src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o \ng++-5.4.0 -Isrc/libcamera/4ab8042@@camera@sha -Isrc/libcamera -I../../src/libcamera -Iinclude -I../../include -I../../include/android/hardware/libhardware/include -I../../include/android/metadata -I../../include/android/system/core/include -Iinclude/libcamera -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wnon-virtual-dtor -Wextra -Werror -std=c++17 -g -include config.h -fPIC -pthread -MD -MQ 'src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o' -MF 'src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o.d' -o 'src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o' -c ../../src/libcamera/event_notifier.cpp\nIn file included from ../../include/libcamera/object.h:14:0,\n from ../../include/libcamera/event_notifier.h:10,\n from ../../src/libcamera/event_notifier.cpp:8:\n../../include/libcamera/bound_method.h:217:64: error: ‘maybe_unused’ attribute directive ignored [-Werror=attributes]\n R activate(Args... args, [[maybe_unused]] bool deleteMethod = false) override\n ^\nIn file included from ../../include/libcamera/event_notifier.h:11:0,\n from ../../src/libcamera/event_notifier.cpp:8:\n../../include/libcamera/signal.h: In member function ‘void libcamera::Signal::disconnect()’:\n../../include/libcamera/signal.h:73:66: error: ‘maybe_unused’ attribute directive ignored [-Werror=attributes]\n SignalBase::disconnect([]([[maybe_unused]] SlotList::iterator &iter) {\n ^\n../../include/libcamera/signal.h: In instantiation of ‘libcamera::Signal::disconnect()::::iterator&)> [with Args = {libcamera::EventNotifier*}; std::__cxx11::list::iterator = std::_List_iterator]’:\n../../include/libcamera/signal.h:73:27: required from ‘struct libcamera::Signal::disconnect() [with Args = {libcamera::EventNotifier*}]::::iterator&)>’\n../../include/libcamera/signal.h:73:25: required from ‘void libcamera::Signal::disconnect() [with Args = {libcamera::EventNotifier*}]’\n../../include/libcamera/signal.h:44:13: required from ‘libcamera::Signal::~Signal() [with Args = {libcamera::EventNotifier*}]’\n../../src/libcamera/event_notifier.cpp:67:56: required from here\n../../include/libcamera/signal.h:73:66: error: unused parameter ‘iter’ [-Werror=unused-parameter]\ncc1plus: all warnings being treated as errors\n\nI'd rather have\n\n../../meson.build:66:8: ERROR: Problem encountered: gcc version is too old, libcamera requires 7.0 or newer\n\n:-)\n\n> Anyway,\n> \n> Reviewed-by: Kieran Bingham \n> \n> Still stands.\n> \n> > +\n> > + # gcc 7.1 introduced processor-specific ABI breakages related to parameter\n> > + # passing on ARM platforms. This generates a large number of messages\n> > + # during compilation with gcc >=7.1 until gcc 9. Silence them.\n> > + if (host_machine.cpu_family() == 'arm' and\n> > + cc.version().version_compare('>=7.1') and\n> > + cc.version().version_compare('<9'))\n> > + cpp_arguments += [\n> > + '-Wno-psabi',\n> > + ]\n> > + endif\n> > +endif\n> > +\n> > # We use C99 designated initializers for arrays as C++ has no equivalent\n> > # feature. Both gcc and clang support this extension, but recent\n> > # versions of clang generate a warning that needs to be disabled.\n> > @@ -71,16 +88,6 @@ if cc.has_argument('-Wno-c99-designator')\n> > ]\n> > endif\n> > \n> > -# gcc 7.1 introduced processor-specific ABI breakages related to parameter\n> > -# passing on ARM platforms. This generates a large number of messages during\n> > -# compilation with gcc >=7.1 until gcc 9. Silence them.\n> > -if (host_machine.cpu_family() == 'arm' and cc.get_id() == 'gcc' and\n> > - cc.version().version_compare('>=7.1') and cc.version().version_compare('<9'))\n> > - cpp_arguments += [\n> > - '-Wno-psabi',\n> > - ]\n> > -endif\n> > -\n> > c_arguments += common_arguments\n> > cpp_arguments += common_arguments\n> >","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 91513BD87C\n\tfor ;\n\tMon, 24 Aug 2020 17:57:46 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id EF65A62818;\n\tMon, 24 Aug 2020 19:57:45 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id BD5AB616B1\n\tfor ;\n\tMon, 24 Aug 2020 19:57:44 +0200 (CEST)","from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi\n\t[62.78.145.57])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 47C8C9CE;\n\tMon, 24 Aug 2020 19:57:44 +0200 (CEST)"],"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=\"e+baF77z\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1598291864;\n\tbh=5E3MNrboVc299Ag1a8O1kx/x3PM2cwB/RJ0tbOwIJyc=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=e+baF77zrofqbyJGxFAVCpxplDOMWWi4MrX3xKKYYkF4AnlUR9T+1pNz0+O3ZhL6Q\n\tuqcSI/+KyLD2BbXP/rxfHVvVUTUE+CHVra67FXG6hgZ7nEAShv9SEP/fJwmsOaIm/S\n\t37YHHWYgbGr7llNHk6i/5tihmW1t6I8t6idEwkVE=","Date":"Mon, 24 Aug 2020 20:57:24 +0300","From":"Laurent Pinchart ","To":"Kieran Bingham ","Message-ID":"<20200824175724.GI6002@pendragon.ideasonboard.com>","References":"<20200822200037.20892-2-laurent.pinchart@ideasonboard.com>\n\t<20200822200454.21718-1-laurent.pinchart@ideasonboard.com>\n\t<64ba9b42-9ee0-e40f-6b5c-f749d74a4cb6@ideasonboard.com>","MIME-Version":"1.0","Content-Disposition":"inline","In-Reply-To":"<64ba9b42-9ee0-e40f-6b5c-f749d74a4cb6@ideasonboard.com>","Subject":"Re: [libcamera-devel] [PATCH v1.1 1/5] meson: Switch to C++17","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","Cc":"libcamera-devel@lists.libcamera.org","Content-Type":"text/plain; charset=\"utf-8\"","Content-Transfer-Encoding":"base64","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":12131,"web_url":"https://patchwork.libcamera.org/comment/12131/","msgid":"<20200824214126.GF594558@oden.dyn.berto.se>","date":"2020-08-24T21:41:26","subject":"Re: [libcamera-devel] [PATCH v1.1 1/5] meson: Switch to C++17","submitter":{"id":5,"url":"https://patchwork.libcamera.org/api/people/5/","name":"Niklas Söderlund","email":"niklas.soderlund@ragnatech.se"},"content":"Hi Laurent,\n\nThanks for your work.\n\nOn 2020-08-24 20:57:24 +0300, Laurent Pinchart wrote:\n> Hi Kieran,\n> \n> On Mon, Aug 24, 2020 at 10:52:53AM +0100, Kieran Bingham wrote:\n> > On 22/08/2020 21:04, Laurent Pinchart wrote:\n> > > Due to popular request, move from C++14 to C++17. This will allow\n> > > dropping some custom constructs (such as a custom utils::clamp),\n> > > benefiting from new language features, and dropping gcc 5 and 6 from the\n> > > compilation tests.\n> > > \n> > > Signed-off-by: Laurent Pinchart \n> > > ---\n> > > Changes since v1:\n> > > \n> > > - Update documentation\n> > > - Print an error message when detecting a too old compiler\n> > \n> > Ok, some useful additions... reading. ..\n> > \n> > > ---\n> > > Documentation/coding-style.rst | 5 ++---\n> > > meson.build | 29 ++++++++++++++++++-----------\n> > > 2 files changed, 20 insertions(+), 14 deletions(-)\n> > > \n> > > diff --git a/Documentation/coding-style.rst b/Documentation/coding-style.rst\n> > > index 7acba37b8de8..7c56a1b70014 100644\n> > > --- a/Documentation/coding-style.rst\n> > > +++ b/Documentation/coding-style.rst\n> > > @@ -88,13 +88,12 @@ headers, and with double quotes for other libcamera headers.\n> > > C++ Specific Rules\n> > > ------------------\n> > > \n> > > -The code shall be implemented in C++14, with the following caveats:\n> > > +The code shall be implemented in C++17, with the following caveats:\n> > > \n> > > * Type inference (auto and decltype) shall be used with caution, to avoid\n> > > drifting towards an untyped language.\n> > > * The explicit, override and final specifiers are to be used where applicable.\n> > > -* General-purpose smart pointers (std::unique_ptr) deprecate std::auto_ptr.\n> > > - Smart pointers, as well as shared pointers and weak pointers, shall not be\n> > > +* Smart pointers, as well as shared pointers and weak pointers, shall not be\n> > > overused.\n> > > * Classes are encouraged to define move constructors and assignment operators\n> > > where applicable, and generally make use of the features offered by rvalue\n> > > diff --git a/meson.build b/meson.build\n> > > index ec54e68f3635..cf2636d97100 100644\n> > > --- a/meson.build\n> > > +++ b/meson.build\n> > > @@ -6,7 +6,7 @@ project('libcamera', 'c', 'cpp',\n> > > default_options : [\n> > > 'werror=true',\n> > > 'warning_level=2',\n> > > - 'cpp_std=c++14',\n> > > + 'cpp_std=c++17',\n> > > ],\n> > > license : 'LGPL 2.1+')\n> > > \n> > > @@ -62,6 +62,23 @@ if cc.get_id() == 'clang'\n> > > endif\n> > > endif\n> > > \n> > > +if cc.get_id() == 'gcc'\n> > > + if cc.version().version_compare('<7')\n> > > + error('gcc version is too old, libcamera requires 7.0 or newer')\n> > > + endif\n> > \n> > Clang v5 or greater is required for C++17. Do we need to catch that too?\n> > or is that considered old enough that we're not going to hit it.\n> \n> The lowest clang version installed on my system is 6.0, so I haven't\n> considered this. It's a good point, I'll add a check.\n\nWith this check added,\n\nReviewed-by: Niklas Söderlund \n\n> \n> > I think it looks like Clang 5 was released around September 2017, while\n> > GCC 7.1 was released earlier in May 2017.\n> > \n> > That said, wouldn't the compiler warn us quite verbosely if it didn't\n> > support C++17 ?\n> > \n> > I.e. .. do /we/ really need to do this check here in meson?\n> \n> Here's how the compiler warns me on gcc 5:\n> \n> [4/281] Compiling C++ object 'src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o'\n> FAILED: src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o \n> g++-5.4.0 -Isrc/libcamera/4ab8042@@camera@sha -Isrc/libcamera -I../../src/libcamera -Iinclude -I../../include -I../../include/android/hardware/libhardware/include -I../../include/android/metadata -I../../include/android/system/core/include -Iinclude/libcamera -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wnon-virtual-dtor -Wextra -Werror -std=c++17 -g -include config.h -fPIC -pthread -MD -MQ 'src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o' -MF 'src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o.d' -o 'src/libcamera/4ab8042@@camera@sha/event_notifier.cpp.o' -c ../../src/libcamera/event_notifier.cpp\n> In file included from ../../include/libcamera/object.h:14:0,\n> from ../../include/libcamera/event_notifier.h:10,\n> from ../../src/libcamera/event_notifier.cpp:8:\n> ../../include/libcamera/bound_method.h:217:64: error: ‘maybe_unused’ attribute directive ignored [-Werror=attributes]\n> R activate(Args... args, [[maybe_unused]] bool deleteMethod = false) override\n> ^\n> In file included from ../../include/libcamera/event_notifier.h:11:0,\n> from ../../src/libcamera/event_notifier.cpp:8:\n> ../../include/libcamera/signal.h: In member function ‘void libcamera::Signal::disconnect()’:\n> ../../include/libcamera/signal.h:73:66: error: ‘maybe_unused’ attribute directive ignored [-Werror=attributes]\n> SignalBase::disconnect([]([[maybe_unused]] SlotList::iterator &iter) {\n> ^\n> ../../include/libcamera/signal.h: In instantiation of ‘libcamera::Signal::disconnect()::::iterator&)> [with Args = {libcamera::EventNotifier*}; std::__cxx11::list::iterator = std::_List_iterator]’:\n> ../../include/libcamera/signal.h:73:27: required from ‘struct libcamera::Signal::disconnect() [with Args = {libcamera::EventNotifier*}]::::iterator&)>’\n> ../../include/libcamera/signal.h:73:25: required from ‘void libcamera::Signal::disconnect() [with Args = {libcamera::EventNotifier*}]’\n> ../../include/libcamera/signal.h:44:13: required from ‘libcamera::Signal::~Signal() [with Args = {libcamera::EventNotifier*}]’\n> ../../src/libcamera/event_notifier.cpp:67:56: required from here\n> ../../include/libcamera/signal.h:73:66: error: unused parameter ‘iter’ [-Werror=unused-parameter]\n> cc1plus: all warnings being treated as errors\n> \n> I'd rather have\n> \n> ../../meson.build:66:8: ERROR: Problem encountered: gcc version is too old, libcamera requires 7.0 or newer\n> \n> :-)\n> \n> > Anyway,\n> > \n> > Reviewed-by: Kieran Bingham \n> > \n> > Still stands.\n> > \n> > > +\n> > > + # gcc 7.1 introduced processor-specific ABI breakages related to parameter\n> > > + # passing on ARM platforms. This generates a large number of messages\n> > > + # during compilation with gcc >=7.1 until gcc 9. Silence them.\n> > > + if (host_machine.cpu_family() == 'arm' and\n> > > + cc.version().version_compare('>=7.1') and\n> > > + cc.version().version_compare('<9'))\n> > > + cpp_arguments += [\n> > > + '-Wno-psabi',\n> > > + ]\n> > > + endif\n> > > +endif\n> > > +\n> > > # We use C99 designated initializers for arrays as C++ has no equivalent\n> > > # feature. Both gcc and clang support this extension, but recent\n> > > # versions of clang generate a warning that needs to be disabled.\n> > > @@ -71,16 +88,6 @@ if cc.has_argument('-Wno-c99-designator')\n> > > ]\n> > > endif\n> > > \n> > > -# gcc 7.1 introduced processor-specific ABI breakages related to parameter\n> > > -# passing on ARM platforms. This generates a large number of messages during\n> > > -# compilation with gcc >=7.1 until gcc 9. Silence them.\n> > > -if (host_machine.cpu_family() == 'arm' and cc.get_id() == 'gcc' and\n> > > - cc.version().version_compare('>=7.1') and cc.version().version_compare('<9'))\n> > > - cpp_arguments += [\n> > > - '-Wno-psabi',\n> > > - ]\n> > > -endif\n> > > -\n> > > c_arguments += common_arguments\n> > > cpp_arguments += common_arguments\n> > > \n> \n> -- \n> Regards,\n> \n> Laurent Pinchart\n> _______________________________________________\n> libcamera-devel mailing list\n> libcamera-devel@lists.libcamera.org\n> https://lists.libcamera.org/listinfo/libcamera-devel","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 E8AEABD87C\n\tfor ;\n\tMon, 24 Aug 2020 21:41:29 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id B4D0862818;\n\tMon, 24 Aug 2020 23:41:29 +0200 (CEST)","from mail-lj1-x243.google.com (mail-lj1-x243.google.com\n\t[IPv6:2a00:1450:4864:20::243])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 91F47616B1\n\tfor ;\n\tMon, 24 Aug 2020 23:41:28 +0200 (CEST)","by mail-lj1-x243.google.com with SMTP id y2so11425006ljc.1\n\tfor ;\n\tMon, 24 Aug 2020 14:41:28 -0700 (PDT)","from localhost (h-209-203.A463.priv.bahnhof.se. 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