[{"id":14433,"web_url":"https://patchwork.libcamera.org/comment/14433/","msgid":"","date":"2021-01-04T05:54:21","subject":"Re: [libcamera-devel] [PATCH] libcamera: revert C++17 specific code\n\tfor public API","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Jean-Michel,\n\nThank you for the patch.\n\nOn Thu, Dec 31, 2020 at 04:47:10PM +0100, Jean-Michel Hautbois wrote:\n> Some applications may not be compliant with C++17 (Chromium, as an\n> example). Keep the C++17 features for libcamera internals, and C++14\n> compliance for public API.\n\nThis is (unfortunately :-)) a good point. I was expecting Chromium to\nuse a more recent C++ version, I'm a bit surprised. There seem to be two\nseparate questions here:\n\n- Could we build the libcamera support in Chromium with C++17\n (specifying the C++ version explicitly in the BUILD.gn file in the\n corresponding subdirectory, overriding the default C++14 version) ?\n\n- As a more general question, can we expect C++17 support in the not too\n distant future in code that will use libcamera, or is that an\n unreasonable expectation and should we stick to c++14 in the public\n API ?\n\nIf the answer to the first question is no, then we won't have a choice\nfor the second question.\n\nWe could stick to C++14 in the public API as it should not block us (at\nleast for now), this revert isn't that bad. I'm however concerned that\nC++17 features may creep in unnoticed in the API, as we can't test\nbuilding libcamera with C++14, given that the internals depend on C++17.\n\n> This reverts commits 8e42c2feb7ff7c350ffbbf97dd963dfd54e21faa and\n> 6cbdc2859963e17bc897a4022f1d68170477d888.\n\nReverts are usually submitted separately, to make is easier to track\nchanges.\n\n> Signed-off-by: Jean-Michel Hautbois \n> ---\n> include/libcamera/bound_method.h | 2 +-\n> include/libcamera/controls.h | 24 +++++------\n> include/libcamera/object.h | 2 +-\n> include/libcamera/signal.h | 4 +-\n> include/libcamera/span.h | 70 +++++++++++++++-----------------\n> 5 files changed, 48 insertions(+), 54 deletions(-)\n> \n> diff --git a/include/libcamera/bound_method.h b/include/libcamera/bound_method.h\n> index feac51da..95a95653 100644\n> --- a/include/libcamera/bound_method.h\n> +++ b/include/libcamera/bound_method.h\n> @@ -63,7 +63,7 @@ public:\n> \t}\n> \tvirtual ~BoundMethodBase() = default;\n> \n> -\ttemplate> * = nullptr>\n> +\ttemplate::value> * = nullptr>\n> \tbool match(T *obj) { return obj == obj_; }\n> \tbool match(Object *object) { return object == object_; }\n> \n> diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h\n> index 3634dc43..3b7f3347 100644\n> --- a/include/libcamera/controls.h\n> +++ b/include/libcamera/controls.h\n> @@ -96,9 +96,9 @@ public:\n> \tControlValue();\n> \n> #ifndef __DOXYGEN__\n> -\ttemplate &&\n> +\ttemplate::value &&\n> \t\t\t\t\t\t details::control_type::value &&\n> -\t\t\t\t\t\t !std::is_same_v>,\n> +\t\t\t\t\t\t !std::is_same>::value,\n> \t\t\t\t\t\t std::nullptr_t> = nullptr>\n> \tControlValue(const T &value)\n> \t\t: type_(ControlTypeNone), numElements_(0)\n> @@ -107,8 +107,8 @@ public:\n> \t\t &value, 1, sizeof(T));\n> \t}\n> \n> -\ttemplate ||\n> -\t\t\t\t\t\t std::is_same_v>,\n> +\ttemplate::value ||\n> +\t\t\t\t\t\t std::is_same>::value,\n> \t\t\t\t\t\t std::nullptr_t> = nullptr>\n> #else\n> \ttemplate\n> @@ -141,8 +141,8 @@ public:\n> \t}\n> \n> #ifndef __DOXYGEN__\n> -\ttemplate &&\n> -\t\t\t\t\t\t !std::is_same_v>,\n> +\ttemplate::value &&\n> +\t\t\t\t\t\t !std::is_same>::value,\n> \t\t\t\t\t\t std::nullptr_t> = nullptr>\n> \tT get() const\n> \t{\n> @@ -152,8 +152,8 @@ public:\n> \t\treturn *reinterpret_cast(data().data());\n> \t}\n> \n> -\ttemplate ||\n> -\t\t\t\t\t\t std::is_same_v>,\n> +\ttemplate::value ||\n> +\t\t\t\t\t\t std::is_same>::value,\n> \t\t\t\t\t\t std::nullptr_t> = nullptr>\n> #else\n> \ttemplate\n> @@ -169,8 +169,8 @@ public:\n> \t}\n> \n> #ifndef __DOXYGEN__\n> -\ttemplate &&\n> -\t\t\t\t\t\t !std::is_same_v>,\n> +\ttemplate::value &&\n> +\t\t\t\t\t\t !std::is_same>::value,\n> \t\t\t\t\t\t std::nullptr_t> = nullptr>\n> \tvoid set(const T &value)\n> \t{\n> @@ -178,8 +178,8 @@ public:\n> \t\t reinterpret_cast(&value), 1, sizeof(T));\n> \t}\n> \n> -\ttemplate ||\n> -\t\t\t\t\t\t std::is_same_v>,\n> +\ttemplate::value ||\n> +\t\t\t\t\t\t std::is_same>::value,\n> \t\t\t\t\t\t std::nullptr_t> = nullptr>\n> #else\n> \ttemplate\n> diff --git a/include/libcamera/object.h b/include/libcamera/object.h\n> index 423208db..a1882f05 100644\n> --- a/include/libcamera/object.h\n> +++ b/include/libcamera/object.h\n> @@ -32,7 +32,7 @@ public:\n> \tvoid postMessage(std::unique_ptr msg);\n> \n> \ttemplate -\t\t typename std::enable_if_t> * = nullptr>\n> +\t\t typename std::enable_if_t::value> * = nullptr>\n> \tR invokeMethod(R (T::*func)(FuncArgs...), ConnectionType type,\n> \t\t Args... args)\n> \t{\n> diff --git a/include/libcamera/signal.h b/include/libcamera/signal.h\n> index 46d917d5..5bcd7a77 100644\n> --- a/include/libcamera/signal.h\n> +++ b/include/libcamera/signal.h\n> @@ -44,7 +44,7 @@ public:\n> \t}\n> \n> #ifndef __DOXYGEN__\n> -\ttemplate> * = nullptr>\n> +\ttemplate::value> * = nullptr>\n> \tvoid connect(T *obj, R (T::*func)(Args...),\n> \t\t ConnectionType type = ConnectionTypeAuto)\n> \t{\n> @@ -52,7 +52,7 @@ public:\n> \t\tSignalBase::connect(new BoundMethodMember(obj, object, func, type));\n> \t}\n> \n> -\ttemplate> * = nullptr>\n> +\ttemplate::value> * = nullptr>\n> #else\n> \ttemplate\n> #endif\n> diff --git a/include/libcamera/span.h b/include/libcamera/span.h\n> index e7ffef12..91e9f974 100644\n> --- a/include/libcamera/span.h\n> +++ b/include/libcamera/span.h\n> @@ -31,9 +31,6 @@ template\n> struct is_array> : public std::true_type {\n> };\n> \n> -template\n> -inline constexpr bool is_array_v = is_array::value;\n> -\n> template\n> struct is_span : public std::false_type {\n> };\n> @@ -42,9 +39,6 @@ template\n> struct is_span> : public std::true_type {\n> };\n> \n> -template\n> -inline constexpr bool is_span_v = is_span::value;\n> -\n> } /* namespace details */\n> \n> namespace utils {\n> @@ -131,8 +125,8 @@ public:\n> \n> \ttemplate\n> \tconstexpr Span(element_type (&arr)[N],\n> -\t\t std::enable_if_t (*)[],\n> -\t\t\t\t\t\t\t element_type (*)[]> &&\n> +\t\t std::enable_if_t (*)[],\n> +\t\t\t\t\t\t\t element_type (*)[]>::value &&\n> \t\t\t\t\tN == Extent,\n> \t\t\t\t\tstd::nullptr_t> = nullptr) noexcept\n> \t\t: data_(arr)\n> @@ -141,8 +135,8 @@ public:\n> \n> \ttemplate\n> \tconstexpr Span(std::array &arr,\n> -\t\t std::enable_if_t (*)[],\n> -\t\t\t\t\t\t\t element_type (*)[]> &&\n> +\t\t std::enable_if_t (*)[],\n> +\t\t\t\t\t\t\t element_type (*)[]>::value &&\n> \t\t\t\t\tN == Extent,\n> \t\t\t\t\tstd::nullptr_t> = nullptr) noexcept\n> \t\t: data_(arr.data())\n> @@ -151,8 +145,8 @@ public:\n> \n> \ttemplate\n> \tconstexpr Span(const std::array &arr,\n> -\t\t std::enable_if_t (*)[],\n> -\t\t\t\t\t\t\t element_type (*)[]> &&\n> +\t\t std::enable_if_t (*)[],\n> +\t\t\t\t\t\t\t element_type (*)[]>::value &&\n> \t\t\t\t\tN == Extent,\n> \t\t\t\t\tstd::nullptr_t> = nullptr) noexcept\n> \t\t: data_(arr.data())\n> @@ -161,11 +155,11 @@ public:\n> \n> \ttemplate\n> \texplicit constexpr Span(Container &cont,\n> -\t\t\t\tstd::enable_if_t &&\n> -\t\t\t\t\t\t !details::is_array_v &&\n> -\t\t\t\t\t\t !std::is_array_v &&\n> -\t\t\t\t\t\t std::is_convertible_v (*)[],\n> -\t\t\t\t\t\t\t\t element_type (*)[]>,\n> +\t\t\t\tstd::enable_if_t::value &&\n> +\t\t\t\t\t\t !details::is_array::value &&\n> +\t\t\t\t\t\t !std::is_array::value &&\n> +\t\t\t\t\t\t std::is_convertible (*)[],\n> +\t\t\t\t\t\t\t\t element_type (*)[]>::value,\n> \t\t\t\t\t\t std::nullptr_t> = nullptr)\n> \t\t: data_(utils::data(cont))\n> \t{\n> @@ -173,11 +167,11 @@ public:\n> \n> \ttemplate\n> \texplicit constexpr Span(const Container &cont,\n> -\t\t\t\tstd::enable_if_t &&\n> -\t\t\t\t\t\t !details::is_array_v &&\n> -\t\t\t\t\t\t !std::is_array_v &&\n> -\t\t\t\t\t\t std::is_convertible_v (*)[],\n> -\t\t\t\t\t\t\t\t element_type (*)[]>,\n> +\t\t\t\tstd::enable_if_t::value &&\n> +\t\t\t\t\t\t !details::is_array::value &&\n> +\t\t\t\t\t\t !std::is_array::value &&\n> +\t\t\t\t\t\t std::is_convertible (*)[],\n> +\t\t\t\t\t\t\t\t element_type (*)[]>::value,\n> \t\t\t\t\t\t std::nullptr_t> = nullptr)\n> \t\t: data_(utils::data(cont))\n> \t{\n> @@ -186,7 +180,7 @@ public:\n> \n> \ttemplate\n> \texplicit constexpr Span(const Span &s,\n> -\t\t\t\tstd::enable_if_t &&\n> +\t\t\t\tstd::enable_if_t::value &&\n> \t\t\t\t\t\t N == Extent,\n> \t\t\t\t\t\t std::nullptr_t> = nullptr) noexcept\n> \t\t: data_(s.data())\n> @@ -299,8 +293,8 @@ public:\n> \n> \ttemplate\n> \tconstexpr Span(element_type (&arr)[N],\n> -\t\t std::enable_if_t (*)[],\n> -\t\t\t\t\t\t\t element_type (*)[]>,\n> +\t\t std::enable_if_t (*)[],\n> +\t\t\t\t\t\t\t element_type (*)[]>::value,\n> \t\t\t\t\tstd::nullptr_t> = nullptr) noexcept\n> \t\t: data_(arr), size_(N)\n> \t{\n> @@ -308,8 +302,8 @@ public:\n> \n> \ttemplate\n> \tconstexpr Span(std::array &arr,\n> -\t\t std::enable_if_t (*)[],\n> -\t\t\t\t\t\t\t element_type (*)[]>,\n> +\t\t std::enable_if_t (*)[],\n> +\t\t\t\t\t\t\t element_type (*)[]>::value,\n> \t\t\t\t\tstd::nullptr_t> = nullptr) noexcept\n> \t\t: data_(utils::data(arr)), size_(N)\n> \t{\n> @@ -323,11 +317,11 @@ public:\n> \n> \ttemplate\n> \tconstexpr Span(Container &cont,\n> -\t\t std::enable_if_t &&\n> -\t\t\t\t\t!details::is_array_v &&\n> -\t\t\t\t\t!std::is_array_v &&\n> -\t\t\t\t\tstd::is_convertible_v (*)[],\n> -\t\t\t\t\t\t\t element_type (*)[]>,\n> +\t\t std::enable_if_t::value &&\n> +\t\t\t\t\t!details::is_array::value &&\n> +\t\t\t\t\t!std::is_array::value &&\n> +\t\t\t\t\tstd::is_convertible (*)[],\n> +\t\t\t\t\t\t\t element_type (*)[]>::value,\n> \t\t\t\t\tstd::nullptr_t> = nullptr)\n> \t\t: data_(utils::data(cont)), size_(utils::size(cont))\n> \t{\n> @@ -335,11 +329,11 @@ public:\n> \n> \ttemplate\n> \tconstexpr Span(const Container &cont,\n> -\t\t std::enable_if_t &&\n> -\t\t\t\t\t!details::is_array_v &&\n> -\t\t\t\t\t!std::is_array_v &&\n> -\t\t\t\t\tstd::is_convertible_v (*)[],\n> -\t\t\t\t\t\t\t element_type (*)[]>,\n> +\t\t std::enable_if_t::value &&\n> +\t\t\t\t\t!details::is_array::value &&\n> +\t\t\t\t\t!std::is_array::value &&\n> +\t\t\t\t\tstd::is_convertible (*)[],\n> +\t\t\t\t\t\t\t element_type (*)[]>::value,\n> \t\t\t\t\tstd::nullptr_t> = nullptr)\n> \t\t: data_(utils::data(cont)), size_(utils::size(cont))\n> \t{\n> @@ -347,7 +341,7 @@ public:\n> \n> \ttemplate\n> \tconstexpr Span(const Span &s,\n> -\t\t std::enable_if_t,\n> +\t\t std::enable_if_t::value,\n> \t\t\t\t\tstd::nullptr_t> = nullptr) noexcept\n> \t\t: data_(s.data()), size_(s.size())\n> \t{","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 89035C0F1A\n\tfor ;\n\tMon, 4 Jan 2021 05:54:36 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id DA14E62000;\n\tMon, 4 Jan 2021 06:54:35 +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 F35A960318\n\tfor ;\n\tMon, 4 Jan 2021 06:54:33 +0100 (CET)","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 2604E2E0;\n\tMon, 4 Jan 2021 06:54:33 +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=\"BFttwGvr\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1609739673;\n\tbh=/5F/9tACPgo7IZrF+JDUAWc4wx/XYiW8dAVaa64Qld8=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=BFttwGvrmU/cRXFOo+NNHTfxzjh6NyZ1CWQyHiwoxw0f/KFSGR2HZlDzxDCbJkF/I\n\tvKB/8d0AI0dWZPoGx/KozQFJ9a7jsZs7ldoBnat26GCnt7WN9ashxsdyNV2nbuDxcx\n\t67r1KbBWqs+JJn0iDC5OgiAhf4LIMoA/oaV2U78c=","Date":"Mon, 4 Jan 2021 07:54:21 +0200","From":"Laurent Pinchart ","To":"Jean-Michel Hautbois ","Message-ID":"","References":"<20201231154711.207852-1-jeanmichel.hautbois@ideasonboard.com>","MIME-Version":"1.0","Content-Disposition":"inline","In-Reply-To":"<20201231154711.207852-1-jeanmichel.hautbois@ideasonboard.com>","Subject":"Re: [libcamera-devel] [PATCH] libcamera: revert C++17 specific code\n\tfor public API","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=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":14451,"web_url":"https://patchwork.libcamera.org/comment/14451/","msgid":"","date":"2021-01-06T09:28:38","subject":"Re: [libcamera-devel] [PATCH] libcamera: revert C++17 specific code\n\tfor public API","submitter":{"id":8,"url":"https://patchwork.libcamera.org/api/people/8/","name":"Shik Chen","email":"shik@google.com"},"content":"Hi all,\n\nOn Mon, Jan 4, 2021 at 1:54 PM Laurent Pinchart\n wrote:\n>\n> Hi Jean-Michel,\n>\n> Thank you for the patch.\n>\n> On Thu, Dec 31, 2020 at 04:47:10PM +0100, Jean-Michel Hautbois wrote:\n> > Some applications may not be compliant with C++17 (Chromium, as an\n> > example). Keep the C++17 features for libcamera internals, and C++14\n> > compliance for public API.\n>\n> This is (unfortunately :-)) a good point. I was expecting Chromium to\n> use a more recent C++ version, I'm a bit surprised. There seem to be two\n> separate questions here:\n>\n> - Could we build the libcamera support in Chromium with C++17\n> (specifying the C++ version explicitly in the BUILD.gn file in the\n> corresponding subdirectory, overriding the default C++14 version) ?\n>\n> - As a more general question, can we expect C++17 support in the not too\n> distant future in code that will use libcamera, or is that an\n> unreasonable expectation and should we stick to c++14 in the public\n> API ?\n\nSome information for Chromium specifically:\n\nAccording to https://chromium-cpp.appspot.com/:\n> C++17: Not yet supported in Chromium, unlikely before mid-2021\n\nQuote from the tracking bug https://crbug.com/752720#c147:\n> the NaCl toolchain's lack of C++17 support is the sole significant blocker.\n\nThe EOL of NaCl toolchain was punted to June 2022 (it was June 2021):\nhttps://blog.chromium.org/2020/08/changes-to-chrome-app-support-timeline.html\n\n>\n>\n> If the answer to the first question is no, then we won't have a choice\n> for the second question.\n>\n> We could stick to C++14 in the public API as it should not block us (at\n> least for now), this revert isn't that bad. I'm however concerned that\n> C++17 features may creep in unnoticed in the API, as we can't test\n> building libcamera with C++14, given that the internals depend on C++17.\n>\n> > This reverts commits 8e42c2feb7ff7c350ffbbf97dd963dfd54e21faa and\n> > 6cbdc2859963e17bc897a4022f1d68170477d888.\n>\n> Reverts are usually submitted separately, to make is easier to track\n> changes.\n>\n> > Signed-off-by: Jean-Michel Hautbois \n> > ---\n> > include/libcamera/bound_method.h | 2 +-\n> > include/libcamera/controls.h | 24 +++++------\n> > include/libcamera/object.h | 2 +-\n> > include/libcamera/signal.h | 4 +-\n> > include/libcamera/span.h | 70 +++++++++++++++-----------------\n> > 5 files changed, 48 insertions(+), 54 deletions(-)\n> >\n> > diff --git a/include/libcamera/bound_method.h b/include/libcamera/bound_method.h\n> > index feac51da..95a95653 100644\n> > --- a/include/libcamera/bound_method.h\n> > +++ b/include/libcamera/bound_method.h\n> > @@ -63,7 +63,7 @@ public:\n> > }\n> > virtual ~BoundMethodBase() = default;\n> >\n> > - template> * = nullptr>\n> > + template::value> * = nullptr>\n> > bool match(T *obj) { return obj == obj_; }\n> > bool match(Object *object) { return object == object_; }\n> >\n> > diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h\n> > index 3634dc43..3b7f3347 100644\n> > --- a/include/libcamera/controls.h\n> > +++ b/include/libcamera/controls.h\n> > @@ -96,9 +96,9 @@ public:\n> > ControlValue();\n> >\n> > #ifndef __DOXYGEN__\n> > - template &&\n> > + template::value &&\n> > details::control_type::value &&\n> > - !std::is_same_v>,\n> > + !std::is_same>::value,\n> > std::nullptr_t> = nullptr>\n> > ControlValue(const T &value)\n> > : type_(ControlTypeNone), numElements_(0)\n> > @@ -107,8 +107,8 @@ public:\n> > &value, 1, sizeof(T));\n> > }\n> >\n> > - template ||\n> > - std::is_same_v>,\n> > + template::value ||\n> > + std::is_same>::value,\n> > std::nullptr_t> = nullptr>\n> > #else\n> > template\n> > @@ -141,8 +141,8 @@ public:\n> > }\n> >\n> > #ifndef __DOXYGEN__\n> > - template &&\n> > - !std::is_same_v>,\n> > + template::value &&\n> > + !std::is_same>::value,\n> > std::nullptr_t> = nullptr>\n> > T get() const\n> > {\n> > @@ -152,8 +152,8 @@ public:\n> > return *reinterpret_cast(data().data());\n> > }\n> >\n> > - template ||\n> > - std::is_same_v>,\n> > + template::value ||\n> > + std::is_same>::value,\n> > std::nullptr_t> = nullptr>\n> > #else\n> > template\n> > @@ -169,8 +169,8 @@ public:\n> > }\n> >\n> > #ifndef __DOXYGEN__\n> > - template &&\n> > - !std::is_same_v>,\n> > + template::value &&\n> > + !std::is_same>::value,\n> > std::nullptr_t> = nullptr>\n> > void set(const T &value)\n> > {\n> > @@ -178,8 +178,8 @@ public:\n> > reinterpret_cast(&value), 1, sizeof(T));\n> > }\n> >\n> > - template ||\n> > - std::is_same_v>,\n> > + template::value ||\n> > + std::is_same>::value,\n> > std::nullptr_t> = nullptr>\n> > #else\n> > template\n> > diff --git a/include/libcamera/object.h b/include/libcamera/object.h\n> > index 423208db..a1882f05 100644\n> > --- a/include/libcamera/object.h\n> > +++ b/include/libcamera/object.h\n> > @@ -32,7 +32,7 @@ public:\n> > void postMessage(std::unique_ptr msg);\n> >\n> > template > - typename std::enable_if_t> * = nullptr>\n> > + typename std::enable_if_t::value> * = nullptr>\n> > R invokeMethod(R (T::*func)(FuncArgs...), ConnectionType type,\n> > Args... args)\n> > {\n> > diff --git a/include/libcamera/signal.h b/include/libcamera/signal.h\n> > index 46d917d5..5bcd7a77 100644\n> > --- a/include/libcamera/signal.h\n> > +++ b/include/libcamera/signal.h\n> > @@ -44,7 +44,7 @@ public:\n> > }\n> >\n> > #ifndef __DOXYGEN__\n> > - template> * = nullptr>\n> > + template::value> * = nullptr>\n> > void connect(T *obj, R (T::*func)(Args...),\n> > ConnectionType type = ConnectionTypeAuto)\n> > {\n> > @@ -52,7 +52,7 @@ public:\n> > SignalBase::connect(new BoundMethodMember(obj, object, func, type));\n> > }\n> >\n> > - template> * = nullptr>\n> > + template::value> * = nullptr>\n> > #else\n> > template\n> > #endif\n> > diff --git a/include/libcamera/span.h b/include/libcamera/span.h\n> > index e7ffef12..91e9f974 100644\n> > --- a/include/libcamera/span.h\n> > +++ b/include/libcamera/span.h\n> > @@ -31,9 +31,6 @@ template\n> > struct is_array> : public std::true_type {\n> > };\n> >\n> > -template\n> > -inline constexpr bool is_array_v = is_array::value;\n> > -\n> > template\n> > struct is_span : public std::false_type {\n> > };\n> > @@ -42,9 +39,6 @@ template\n> > struct is_span> : public std::true_type {\n> > };\n> >\n> > -template\n> > -inline constexpr bool is_span_v = is_span::value;\n> > -\n> > } /* namespace details */\n> >\n> > namespace utils {\n> > @@ -131,8 +125,8 @@ public:\n> >\n> > template\n> > constexpr Span(element_type (&arr)[N],\n> > - std::enable_if_t (*)[],\n> > - element_type (*)[]> &&\n> > + std::enable_if_t (*)[],\n> > + element_type (*)[]>::value &&\n> > N == Extent,\n> > std::nullptr_t> = nullptr) noexcept\n> > : data_(arr)\n> > @@ -141,8 +135,8 @@ public:\n> >\n> > template\n> > constexpr Span(std::array &arr,\n> > - std::enable_if_t (*)[],\n> > - element_type (*)[]> &&\n> > + std::enable_if_t (*)[],\n> > + element_type (*)[]>::value &&\n> > N == Extent,\n> > std::nullptr_t> = nullptr) noexcept\n> > : data_(arr.data())\n> > @@ -151,8 +145,8 @@ public:\n> >\n> > template\n> > constexpr Span(const std::array &arr,\n> > - std::enable_if_t (*)[],\n> > - element_type (*)[]> &&\n> > + std::enable_if_t (*)[],\n> > + element_type (*)[]>::value &&\n> > N == Extent,\n> > std::nullptr_t> = nullptr) noexcept\n> > : data_(arr.data())\n> > @@ -161,11 +155,11 @@ public:\n> >\n> > template\n> > explicit constexpr Span(Container &cont,\n> > - std::enable_if_t &&\n> > - !details::is_array_v &&\n> > - !std::is_array_v &&\n> > - std::is_convertible_v (*)[],\n> > - element_type (*)[]>,\n> > + std::enable_if_t::value &&\n> > + !details::is_array::value &&\n> > + !std::is_array::value &&\n> > + std::is_convertible (*)[],\n> > + element_type (*)[]>::value,\n> > std::nullptr_t> = nullptr)\n> > : data_(utils::data(cont))\n> > {\n> > @@ -173,11 +167,11 @@ public:\n> >\n> > template\n> > explicit constexpr Span(const Container &cont,\n> > - std::enable_if_t &&\n> > - !details::is_array_v &&\n> > - !std::is_array_v &&\n> > - std::is_convertible_v (*)[],\n> > - element_type (*)[]>,\n> > + std::enable_if_t::value &&\n> > + !details::is_array::value &&\n> > + !std::is_array::value &&\n> > + std::is_convertible (*)[],\n> > + element_type (*)[]>::value,\n> > std::nullptr_t> = nullptr)\n> > : data_(utils::data(cont))\n> > {\n> > @@ -186,7 +180,7 @@ public:\n> >\n> > template\n> > explicit constexpr Span(const Span &s,\n> > - std::enable_if_t &&\n> > + std::enable_if_t::value &&\n> > N == Extent,\n> > std::nullptr_t> = nullptr) noexcept\n> > : data_(s.data())\n> > @@ -299,8 +293,8 @@ public:\n> >\n> > template\n> > constexpr Span(element_type (&arr)[N],\n> > - std::enable_if_t (*)[],\n> > - element_type (*)[]>,\n> > + std::enable_if_t (*)[],\n> > + element_type (*)[]>::value,\n> > std::nullptr_t> = nullptr) noexcept\n> > : data_(arr), size_(N)\n> > {\n> > @@ -308,8 +302,8 @@ public:\n> >\n> > template\n> > constexpr Span(std::array &arr,\n> > - std::enable_if_t (*)[],\n> > - element_type (*)[]>,\n> > + std::enable_if_t (*)[],\n> > + element_type (*)[]>::value,\n> > std::nullptr_t> = nullptr) noexcept\n> > : data_(utils::data(arr)), size_(N)\n> > {\n> > @@ -323,11 +317,11 @@ public:\n> >\n> > template\n> > constexpr Span(Container &cont,\n> > - std::enable_if_t &&\n> > - !details::is_array_v &&\n> > - !std::is_array_v &&\n> > - std::is_convertible_v (*)[],\n> > - element_type (*)[]>,\n> > + std::enable_if_t::value &&\n> > + !details::is_array::value &&\n> > + !std::is_array::value &&\n> > + std::is_convertible (*)[],\n> > + element_type (*)[]>::value,\n> > std::nullptr_t> = nullptr)\n> > : data_(utils::data(cont)), size_(utils::size(cont))\n> > {\n> > @@ -335,11 +329,11 @@ public:\n> >\n> > template\n> > constexpr Span(const Container &cont,\n> > - std::enable_if_t &&\n> > - !details::is_array_v &&\n> > - !std::is_array_v &&\n> > - std::is_convertible_v (*)[],\n> > - element_type (*)[]>,\n> > + std::enable_if_t::value &&\n> > + !details::is_array::value &&\n> > + !std::is_array::value &&\n> > + std::is_convertible (*)[],\n> > + element_type (*)[]>::value,\n> > std::nullptr_t> = nullptr)\n> > : data_(utils::data(cont)), size_(utils::size(cont))\n> > {\n> > @@ -347,7 +341,7 @@ public:\n> >\n> > template\n> > constexpr Span(const Span &s,\n> > - std::enable_if_t,\n> > + std::enable_if_t::value,\n> > std::nullptr_t> = nullptr) noexcept\n> > : data_(s.data()), size_(s.size())\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\n\n- shik","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 B7D2BC0F1C\n\tfor ;\n\tWed, 6 Jan 2021 09:29:08 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 163E76278D;\n\tWed, 6 Jan 2021 10:29:08 +0100 (CET)","from mail-qt1-x829.google.com (mail-qt1-x829.google.com\n\t[IPv6:2607:f8b0:4864:20::829])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 596A16010B\n\tfor ;\n\tWed, 6 Jan 2021 10:29:06 +0100 (CET)","by mail-qt1-x829.google.com with SMTP id y15so1668825qtv.5\n\tfor ;\n\tWed, 06 Jan 2021 01:29:06 -0800 (PST)"],"Authentication-Results":"lancelot.ideasonboard.com;\n\tdkim=fail reason=\"signature verification failed\" (2048-bit key;\n\tunprotected) header.d=google.com header.i=@google.com\n\theader.b=\"NCfO1ppX\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com;\n\ts=20161025; \n\th=mime-version:references:in-reply-to:from:date:message-id:subject:to\n\t:cc; bh=KrpbCq6N7Bn5WGNZBwBMana8xkc4eqfhRmlHM4pzTNs=;\n\tb=NCfO1ppXy5nlNDP0kRSkqLV/6zoBwwt9yC7QNRBxZB2AMXeDSD1AZpvU8JPPHz2Fb1\n\tdrJltTlfq2lFZ6BJYPuKL4/ckoffvj82MEk303KYHzkB6UyU42iKCYpmDKm3olTdebaJ\n\t3pX49VPxrlQ/k4Du/QJAita2mm9MrdF2MKyYdqlGIV0ttvsNjwfJoXmp9HcyWlu+GY/W\n\tScHC/Sl+zl3sHUxzDLZnUX3JjSxgouJKG7PCj65yZg97UOuJc6xjBit5TFeQecZcBFPH\n\tUETcS0dOgi3kiLvPDFiBGaPoOe32omTB+T7CKhhRrBesDvpqwjrKgCq+X4iQK56QPZaD\n\tYolw==","X-Google-DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed;\n\td=1e100.net; s=20161025;\n\th=x-gm-message-state:mime-version:references:in-reply-to:from:date\n\t:message-id:subject:to:cc;\n\tbh=KrpbCq6N7Bn5WGNZBwBMana8xkc4eqfhRmlHM4pzTNs=;\n\tb=dRcW4PX4yG8e2R2NirUQzoXJu0kLwdkEb6XiwtjN9t8o3Qzyuw4t2su/OfyPlzYLyn\n\tVc8G3b0rpDSD9rHGZkMovOyb7lUQrLtyLtnGVWTyj5tQV9wDGhhSlR7cLo5PfUjEr5R2\n\tSXyLp1OYTKhTjw6vJEWNB6JBt9dQE8MzLd4C41Ijzw1WczU318iyxbXGLnec8UZn6nC+\n\t1+V3dm/WO96ak+upJpmwclHC36sD0HgKM+wMpSDbNoWGmOlKZrLjzydkorqYhpedenlv\n\t+iY5oV3on6a8/UzzRjg8t4LXVTA2jsPoiv62lxHEt3WjyuUR1Y85f6o3FAZqg70xG/Pg\n\ttQlA==","X-Gm-Message-State":"AOAM5322rVr3C0SQfLWiNJp3Dww9b+V3Wv73GimzfFqHOY/BwqzHWc/R\n\tAxf3DVDnOrmKdbMT2nA3/iLHspAljuyAG1ma9r0Oig==","X-Google-Smtp-Source":"ABdhPJyF6vFux/eamA5jwZWpeIW4FXmkNH3jzq8r1VO0vYdtdDtYhxkeWREV6mvSKo6UvCrBWiOZCoOe62z+dPTeGkY=","X-Received":"by 2002:ac8:7c8e:: with SMTP id\n\ty14mr3099473qtv.161.1609925344549; \n\tWed, 06 Jan 2021 01:29:04 -0800 (PST)","MIME-Version":"1.0","References":"<20201231154711.207852-1-jeanmichel.hautbois@ideasonboard.com>\n\t","In-Reply-To":"","From":"Shik Chen ","Date":"Wed, 6 Jan 2021 17:28:38 +0800","Message-ID":"","To":"Laurent Pinchart ","Subject":"Re: [libcamera-devel] [PATCH] libcamera: revert C++17 specific code\n\tfor public API","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=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":14456,"web_url":"https://patchwork.libcamera.org/comment/14456/","msgid":"","date":"2021-01-06T11:47:17","subject":"Re: [libcamera-devel] [PATCH] libcamera: revert C++17 specific code\n\tfor public API","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Shik,\n\nOn Wed, Jan 06, 2021 at 05:28:38PM +0800, Shik Chen wrote:\n> On Mon, Jan 4, 2021 at 1:54 PM Laurent Pinchart wrote:\n> > On Thu, Dec 31, 2020 at 04:47:10PM +0100, Jean-Michel Hautbois wrote:\n> > > Some applications may not be compliant with C++17 (Chromium, as an\n> > > example). Keep the C++17 features for libcamera internals, and C++14\n> > > compliance for public API.\n> >\n> > This is (unfortunately :-)) a good point. I was expecting Chromium to\n> > use a more recent C++ version, I'm a bit surprised. There seem to be two\n> > separate questions here:\n> >\n> > - Could we build the libcamera support in Chromium with C++17\n> > (specifying the C++ version explicitly in the BUILD.gn file in the\n> > corresponding subdirectory, overriding the default C++14 version) ?\n> >\n> > - As a more general question, can we expect C++17 support in the not too\n> > distant future in code that will use libcamera, or is that an\n> > unreasonable expectation and should we stick to c++14 in the public\n> > API ?\n> \n> Some information for Chromium specifically:\n> \n> According to https://chromium-cpp.appspot.com/:\n> > C++17: Not yet supported in Chromium, unlikely before mid-2021\n\nWe found the same information :-)\n\nFor Chromium specifically, I wonder if the libcamera integration code\ncould be compiled with C++-17, with the rest of the code base using\nC++14.\n\n> Quote from the tracking bug https://crbug.com/752720#c147:\n> > the NaCl toolchain's lack of C++17 support is the sole significant blocker.\n> \n> The EOL of NaCl toolchain was punted to June 2022 (it was June 2021):\n> https://blog.chromium.org/2020/08/changes-to-chrome-app-support-timeline.html\n>\n> > If the answer to the first question is no, then we won't have a choice\n> > for the second question.\n> >\n> > We could stick to C++14 in the public API as it should not block us (at\n> > least for now), this revert isn't that bad. I'm however concerned that\n> > C++17 features may creep in unnoticed in the API, as we can't test\n> > building libcamera with C++14, given that the internals depend on C++17.\n> >\n> > > This reverts commits 8e42c2feb7ff7c350ffbbf97dd963dfd54e21faa and\n> > > 6cbdc2859963e17bc897a4022f1d68170477d888.\n> >\n> > Reverts are usually submitted separately, to make is easier to track\n> > changes.\n> >\n> > > Signed-off-by: Jean-Michel Hautbois \n> > > ---\n> > > include/libcamera/bound_method.h | 2 +-\n> > > include/libcamera/controls.h | 24 +++++------\n> > > include/libcamera/object.h | 2 +-\n> > > include/libcamera/signal.h | 4 +-\n> > > include/libcamera/span.h | 70 +++++++++++++++-----------------\n> > > 5 files changed, 48 insertions(+), 54 deletions(-)\n> > >\n> > > diff --git a/include/libcamera/bound_method.h b/include/libcamera/bound_method.h\n> > > index feac51da..95a95653 100644\n> > > --- a/include/libcamera/bound_method.h\n> > > +++ b/include/libcamera/bound_method.h\n> > > @@ -63,7 +63,7 @@ public:\n> > > }\n> > > virtual ~BoundMethodBase() = default;\n> > >\n> > > - template> * = nullptr>\n> > > + template::value> * = nullptr>\n> > > bool match(T *obj) { return obj == obj_; }\n> > > bool match(Object *object) { return object == object_; }\n> > >\n> > > diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h\n> > > index 3634dc43..3b7f3347 100644\n> > > --- a/include/libcamera/controls.h\n> > > +++ b/include/libcamera/controls.h\n> > > @@ -96,9 +96,9 @@ public:\n> > > ControlValue();\n> > >\n> > > #ifndef __DOXYGEN__\n> > > - template &&\n> > > + template::value &&\n> > > details::control_type::value &&\n> > > - !std::is_same_v>,\n> > > + !std::is_same>::value,\n> > > std::nullptr_t> = nullptr>\n> > > ControlValue(const T &value)\n> > > : type_(ControlTypeNone), numElements_(0)\n> > > @@ -107,8 +107,8 @@ public:\n> > > &value, 1, sizeof(T));\n> > > }\n> > >\n> > > - template ||\n> > > - std::is_same_v>,\n> > > + template::value ||\n> > > + std::is_same>::value,\n> > > std::nullptr_t> = nullptr>\n> > > #else\n> > > template\n> > > @@ -141,8 +141,8 @@ public:\n> > > }\n> > >\n> > > #ifndef __DOXYGEN__\n> > > - template &&\n> > > - !std::is_same_v>,\n> > > + template::value &&\n> > > + !std::is_same>::value,\n> > > std::nullptr_t> = nullptr>\n> > > T get() const\n> > > {\n> > > @@ -152,8 +152,8 @@ public:\n> > > return *reinterpret_cast(data().data());\n> > > }\n> > >\n> > > - template ||\n> > > - std::is_same_v>,\n> > > + template::value ||\n> > > + std::is_same>::value,\n> > > std::nullptr_t> = nullptr>\n> > > #else\n> > > template\n> > > @@ -169,8 +169,8 @@ public:\n> > > }\n> > >\n> > > #ifndef __DOXYGEN__\n> > > - template &&\n> > > - !std::is_same_v>,\n> > > + template::value &&\n> > > + !std::is_same>::value,\n> > > std::nullptr_t> = nullptr>\n> > > void set(const T &value)\n> > > {\n> > > @@ -178,8 +178,8 @@ public:\n> > > reinterpret_cast(&value), 1, sizeof(T));\n> > > }\n> > >\n> > > - template ||\n> > > - std::is_same_v>,\n> > > + template::value ||\n> > > + std::is_same>::value,\n> > > std::nullptr_t> = nullptr>\n> > > #else\n> > > template\n> > > diff --git a/include/libcamera/object.h b/include/libcamera/object.h\n> > > index 423208db..a1882f05 100644\n> > > --- a/include/libcamera/object.h\n> > > +++ b/include/libcamera/object.h\n> > > @@ -32,7 +32,7 @@ public:\n> > > void postMessage(std::unique_ptr msg);\n> > >\n> > > template > > - typename std::enable_if_t> * = nullptr>\n> > > + typename std::enable_if_t::value> * = nullptr>\n> > > R invokeMethod(R (T::*func)(FuncArgs...), ConnectionType type,\n> > > Args... args)\n> > > {\n> > > diff --git a/include/libcamera/signal.h b/include/libcamera/signal.h\n> > > index 46d917d5..5bcd7a77 100644\n> > > --- a/include/libcamera/signal.h\n> > > +++ b/include/libcamera/signal.h\n> > > @@ -44,7 +44,7 @@ public:\n> > > }\n> > >\n> > > #ifndef __DOXYGEN__\n> > > - template> * = nullptr>\n> > > + template::value> * = nullptr>\n> > > void connect(T *obj, R (T::*func)(Args...),\n> > > ConnectionType type = ConnectionTypeAuto)\n> > > {\n> > > @@ -52,7 +52,7 @@ public:\n> > > SignalBase::connect(new BoundMethodMember(obj, object, func, type));\n> > > }\n> > >\n> > > - template> * = nullptr>\n> > > + template::value> * = nullptr>\n> > > #else\n> > > template\n> > > #endif\n> > > diff --git a/include/libcamera/span.h b/include/libcamera/span.h\n> > > index e7ffef12..91e9f974 100644\n> > > --- a/include/libcamera/span.h\n> > > +++ b/include/libcamera/span.h\n> > > @@ -31,9 +31,6 @@ template\n> > > struct is_array> : public std::true_type {\n> > > };\n> > >\n> > > -template\n> > > -inline constexpr bool is_array_v = is_array::value;\n> > > -\n> > > template\n> > > struct is_span : public std::false_type {\n> > > };\n> > > @@ -42,9 +39,6 @@ template\n> > > struct is_span> : public std::true_type {\n> > > };\n> > >\n> > > -template\n> > > -inline constexpr bool is_span_v = is_span::value;\n> > > -\n> > > } /* namespace details */\n> > >\n> > > namespace utils {\n> > > @@ -131,8 +125,8 @@ public:\n> > >\n> > > template\n> > > constexpr Span(element_type (&arr)[N],\n> > > - std::enable_if_t (*)[],\n> > > - element_type (*)[]> &&\n> > > + std::enable_if_t (*)[],\n> > > + element_type (*)[]>::value &&\n> > > N == Extent,\n> > > std::nullptr_t> = nullptr) noexcept\n> > > : data_(arr)\n> > > @@ -141,8 +135,8 @@ public:\n> > >\n> > > template\n> > > constexpr Span(std::array &arr,\n> > > - std::enable_if_t (*)[],\n> > > - element_type (*)[]> &&\n> > > + std::enable_if_t (*)[],\n> > > + element_type (*)[]>::value &&\n> > > N == Extent,\n> > > std::nullptr_t> = nullptr) noexcept\n> > > : data_(arr.data())\n> > > @@ -151,8 +145,8 @@ public:\n> > >\n> > > template\n> > > constexpr Span(const std::array &arr,\n> > > - std::enable_if_t (*)[],\n> > > - element_type (*)[]> &&\n> > > + std::enable_if_t (*)[],\n> > > + element_type (*)[]>::value &&\n> > > N == Extent,\n> > > std::nullptr_t> = nullptr) noexcept\n> > > : data_(arr.data())\n> > > @@ -161,11 +155,11 @@ public:\n> > >\n> > > template\n> > > explicit constexpr Span(Container &cont,\n> > > - std::enable_if_t &&\n> > > - !details::is_array_v &&\n> > > - !std::is_array_v &&\n> > > - std::is_convertible_v (*)[],\n> > > - element_type (*)[]>,\n> > > + std::enable_if_t::value &&\n> > > + !details::is_array::value &&\n> > > + !std::is_array::value &&\n> > > + std::is_convertible (*)[],\n> > > + element_type (*)[]>::value,\n> > > std::nullptr_t> = nullptr)\n> > > : data_(utils::data(cont))\n> > > {\n> > > @@ -173,11 +167,11 @@ public:\n> > >\n> > > template\n> > > explicit constexpr Span(const Container &cont,\n> > > - std::enable_if_t &&\n> > > - !details::is_array_v &&\n> > > - !std::is_array_v &&\n> > > - std::is_convertible_v (*)[],\n> > > - element_type (*)[]>,\n> > > + std::enable_if_t::value &&\n> > > + !details::is_array::value &&\n> > > + !std::is_array::value &&\n> > > + std::is_convertible (*)[],\n> > > + element_type (*)[]>::value,\n> > > std::nullptr_t> = nullptr)\n> > > : data_(utils::data(cont))\n> > > {\n> > > @@ -186,7 +180,7 @@ public:\n> > >\n> > > template\n> > > explicit constexpr Span(const Span &s,\n> > > - std::enable_if_t &&\n> > > + std::enable_if_t::value &&\n> > > N == Extent,\n> > > std::nullptr_t> = nullptr) noexcept\n> > > : data_(s.data())\n> > > @@ -299,8 +293,8 @@ public:\n> > >\n> > > template\n> > > constexpr Span(element_type (&arr)[N],\n> > > - std::enable_if_t (*)[],\n> > > - element_type (*)[]>,\n> > > + std::enable_if_t (*)[],\n> > > + element_type (*)[]>::value,\n> > > std::nullptr_t> = nullptr) noexcept\n> > > : data_(arr), size_(N)\n> > > {\n> > > @@ -308,8 +302,8 @@ public:\n> > >\n> > > template\n> > > constexpr Span(std::array &arr,\n> > > - std::enable_if_t (*)[],\n> > > - element_type (*)[]>,\n> > > + std::enable_if_t (*)[],\n> > > + element_type (*)[]>::value,\n> > > std::nullptr_t> = nullptr) noexcept\n> > > : data_(utils::data(arr)), size_(N)\n> > > {\n> > > @@ -323,11 +317,11 @@ public:\n> > >\n> > > template\n> > > constexpr Span(Container &cont,\n> > > - std::enable_if_t &&\n> > > - !details::is_array_v &&\n> > > - !std::is_array_v &&\n> > > - std::is_convertible_v (*)[],\n> > > - element_type (*)[]>,\n> > > + std::enable_if_t::value &&\n> > > + !details::is_array::value &&\n> > > + !std::is_array::value &&\n> > > + std::is_convertible (*)[],\n> > > + element_type (*)[]>::value,\n> > > std::nullptr_t> = nullptr)\n> > > : data_(utils::data(cont)), size_(utils::size(cont))\n> > > {\n> > > @@ -335,11 +329,11 @@ public:\n> > >\n> > > template\n> > > constexpr Span(const Container &cont,\n> > > - std::enable_if_t &&\n> > > - !details::is_array_v &&\n> > > - !std::is_array_v &&\n> > > - std::is_convertible_v (*)[],\n> > > - element_type (*)[]>,\n> > > + std::enable_if_t::value &&\n> > > + !details::is_array::value &&\n> > > + !std::is_array::value &&\n> > > + std::is_convertible (*)[],\n> > > + element_type (*)[]>::value,\n> > > std::nullptr_t> = nullptr)\n> > > : data_(utils::data(cont)), size_(utils::size(cont))\n> > > {\n> > > @@ -347,7 +341,7 @@ public:\n> > >\n> > > template\n> > > constexpr Span(const Span &s,\n> > > - std::enable_if_t,\n> > > + std::enable_if_t::value,\n> > > std::nullptr_t> = nullptr) noexcept\n> > > : data_(s.data()), size_(s.size())\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 18FEEC0F1A\n\tfor ;\n\tWed, 6 Jan 2021 11:47:32 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 4D4BC630BA;\n\tWed, 6 Jan 2021 12:47:31 +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 5BC626010B\n\tfor ;\n\tWed, 6 Jan 2021 12:47:30 +0100 (CET)","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 B9CCB335;\n\tWed, 6 Jan 2021 12:47:29 +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=\"NMrfRTNx\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1609933649;\n\tbh=HpFBlgxAqfmAeSkxvU1ZX9I7ThbcwmXmmrXBxSu+3Kc=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=NMrfRTNxAkGu8MhHIIp1uOljrYfSXkuQh29aw9R7jKV7vd2X4rqYJxxERYv8U481A\n\tKSdWhLcjuDBKyv40cTyiNzK2OInasRwUtQJn2NE3O0NXvWC5WvrJrIZwE3mFsMV5eR\n\t/orpgTD6MgzWDl2r6Q/+nM1v+sOwBXt6KxL7unRE=","Date":"Wed, 6 Jan 2021 13:47:17 +0200","From":"Laurent Pinchart ","To":"Shik Chen ","Message-ID":"","References":"<20201231154711.207852-1-jeanmichel.hautbois@ideasonboard.com>\n\t\n\t","MIME-Version":"1.0","Content-Disposition":"inline","In-Reply-To":"","Subject":"Re: [libcamera-devel] [PATCH] libcamera: revert C++17 specific code\n\tfor public API","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=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]