[{"id":3994,"web_url":"https://patchwork.libcamera.org/comment/3994/","msgid":"<38b5b232-af04-5759-3bf9-60cf38880f74@ideasonboard.com>","date":"2020-03-07T23:01:06","subject":"Re: [libcamera-devel] [PATCH v3 4/7] libcamera: Don't unnecessarily\n\tlink against libatomic","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"Hi Laurent,\n\nOn 07/03/2020 21:13, Laurent Pinchart wrote:\n> libatomic provides atomic operations that are also available as compiler\n> built-ins on most platforms. On some platforms (such as Sparc) linking\n> against libatomic is required to use any atomic operation. libcamera\n> links against libatomic if available for that reason.\n> \n> This however makes libcamera link against libatomic even when not\n> required, if libatomic is available. Restrict this to only the cases\n> where libatomic is required with a link test.\n> \n\nHrm, I thought we discussed and researched this topic when it went in.\n\nI thought I recalled testing this and identifying that even if libatomic\nwas found on the system, and would be available to link - The toolchain\nwould take the internals as a preference and caused no binary change in\nthe output.\n\nBut I won't overly object to this change though.\n\n> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>\n\nReviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>\n\n> ---\n>  meson.build               |  1 +\n>  src/libcamera/meson.build |  2 +-\n>  src/meson.build           | 17 +++++++++++++++++\n>  3 files changed, 19 insertions(+), 1 deletion(-)\n> \n> diff --git a/meson.build b/meson.build\n> index c6e6a934e54e..a1e455249b0d 100644\n> --- a/meson.build\n> +++ b/meson.build\n> @@ -24,6 +24,7 @@ libcamera_version = libcamera_git_version.split('+')[0]\n>  , \n>  # Configure the build environment.\n>  cc = meson.get_compiler('c')\n> +cxx = meson.get_compiler('cpp')\n>  config_h = configuration_data()\n>  \n>  if cc.has_header_symbol('execinfo.h', 'backtrace')\n> diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build\n> index 1b69bc0dee54..ac6f597c6188 100644\n> --- a/src/libcamera/meson.build\n> +++ b/src/libcamera/meson.build\n> @@ -93,7 +93,7 @@ version_cpp = vcs_tag(command : [gen_version, meson.build_root()],\n>  libcamera_sources += version_cpp\n>  \n>  libcamera_deps = [\n> -    cc.find_library('atomic', required: false),\n> +    libatomic_dep,\n>      cc.find_library('dl'),\n>      libudev,\n>      dependency('threads'),\n> diff --git a/src/meson.build b/src/meson.build\n> index d818d8b86d93..abf755936f2b 100644\n> --- a/src/meson.build\n> +++ b/src/meson.build\n\nHrm ... is this the right place for this?\n\nI guess it's not a 'bad' place for it.\nOur top level meson.build is getting busier and busier... and this\npresumably affects only 'src' code (hence being under src) ... but then\n'test/' misses out?\n\nStill I guess test/ may be less likely to use atomics...\n\n\n> @@ -1,3 +1,20 @@\n> +# On some platforms gcc doesn't provide built-ins for atomic operations,\n> +# explicit linking against libatomic is required.\n> +if cxx.links('''\n> +    #include <atomic>\n> +    #include <cstdint>\n> +    int main(void)\n> +    {\n> +        std::atomic<std::uint32_t> u32(0);\n> +        std::atomic<std::uint64_t> u64(0);\n> +        return u32.load() + u64.load();\n> +    }\n> +''')\n> +    libatomic_dep = dependency('', required : false)\n> +else\n> +    libatomic_dep = cc.find_library('atomic')\n> +endif\n> +\n>  if get_option('android')\n>      subdir('android')\n>  endif\n>","headers":{"Return-Path":"<kieran.bingham@ideasonboard.com>","Received":["from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 2EB7460424\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tSun,  8 Mar 2020 00:01:12 +0100 (CET)","from [192.168.0.20]\n\t(cpc89242-aztw30-2-0-cust488.18-1.cable.virginm.net [86.31.129.233])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 92FBD5F;\n\tSun,  8 Mar 2020 00:01:11 +0100 (CET)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1583622071;\n\tbh=XPUmbfYEF89eafGrUJF18iGSW9uj2jSaTUAZftj20eo=;\n\th=Reply-To:Subject:To:References:From:Date:In-Reply-To:From;\n\tb=ThS+jrpAJ1XWNbicidzvOOB9vlbi+aXpvZtUEqmq6kZRlJo5jCIdFjBk1wak0ZCTl\n\t1II+oQ00QrLsLlHaWEe5aBLVLPlV0SoCM3wlO40eV+1OQ3Nvj7TCqqbJpBQBSuhcgU\n\t9TRI4jKOr+/77K0huHm+JzqNuucCsMpy2nmkvl4k=","Reply-To":"kieran.bingham@ideasonboard.com","To":"Laurent Pinchart <laurent.pinchart@ideasonboard.com>,\n\tlibcamera-devel@lists.libcamera.org","References":"<20200307211326.26994-1-laurent.pinchart@ideasonboard.com>\n\t<20200307211326.26994-5-laurent.pinchart@ideasonboard.com>","From":"Kieran Bingham <kieran.bingham@ideasonboard.com>","Openpgp":"preference=signencrypt","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":"<38b5b232-af04-5759-3bf9-60cf38880f74@ideasonboard.com>","Date":"Sat, 7 Mar 2020 23:01:06 +0000","User-Agent":"Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101\n\tThunderbird/60.9.1","MIME-Version":"1.0","In-Reply-To":"<20200307211326.26994-5-laurent.pinchart@ideasonboard.com>","Content-Type":"text/plain; charset=utf-8","Content-Language":"en-GB","Content-Transfer-Encoding":"8bit","Subject":"Re: [libcamera-devel] [PATCH v3 4/7] libcamera: Don't unnecessarily\n\tlink against libatomic","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"<libcamera-devel.lists.libcamera.org>","List-Unsubscribe":"<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>","List-Archive":"<https://lists.libcamera.org/pipermail/libcamera-devel/>","List-Post":"<mailto:libcamera-devel@lists.libcamera.org>","List-Help":"<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>","List-Subscribe":"<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>","X-List-Received-Date":"Sat, 07 Mar 2020 23:01:12 -0000"}},{"id":3998,"web_url":"https://patchwork.libcamera.org/comment/3998/","msgid":"<20200307232714.GB31018@pendragon.ideasonboard.com>","date":"2020-03-07T23:27:14","subject":"Re: [libcamera-devel] [PATCH v3 4/7] libcamera: Don't unnecessarily\n\tlink against libatomic","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Kieran,\n\nOn Sat, Mar 07, 2020 at 11:01:06PM +0000, Kieran Bingham wrote:\n> On 07/03/2020 21:13, Laurent Pinchart wrote:\n> > libatomic provides atomic operations that are also available as compiler\n> > built-ins on most platforms. On some platforms (such as Sparc) linking\n> > against libatomic is required to use any atomic operation. libcamera\n> > links against libatomic if available for that reason.\n> > \n> > This however makes libcamera link against libatomic even when not\n> > required, if libatomic is available. Restrict this to only the cases\n> > where libatomic is required with a link test.\n> \n> Hrm, I thought we discussed and researched this topic when it went in.\n> \n> I thought I recalled testing this and identifying that even if libatomic\n> was found on the system, and would be available to link - The toolchain\n> would take the internals as a preference and caused no binary change in\n> the output.\n> \n> But I won't overly object to this change though.\n\nYou're right, I checked again:\n\n--- libcamera.so.1.hex  2020-03-08 01:25:05.609314371 +0200\n+++ libcamera.so.2.hex  2020-03-08 01:25:13.060315088 +0200\n@@ -35886,7 +35886,7 @@\n 0008c600  6f 6e 00 00 4d 61 6e 75  61 6c 45 78 70 6f 73 75  |on..ManualExposu|\n 0008c610  72 65 00 00 4d 61 6e 75  61 6c 47 61 69 6e 00 00  |re..ManualGain..|\n 0008c620  4c 6f 63 61 74 69 6f 6e  00 00 00 00 76 30 2e 30  |Location....v0.0|\n-0008c630  2e 30 2b 31 31 31 36 2d  38 36 32 33 31 38 36 38  |.0+1116-86231868|\n+0008c630  2e 30 2b 31 31 31 37 2d  33 63 36 37 62 33 34 34  |.0+1117-3c67b344|\n 0008c640  00 00 00 00 42 75 66 66  65 72 00 00 53 65 72 69  |....Buffer..Seri|\n 0008c650  61 6c 69 7a 61 74 69 6f  6e 00 00 00 2e 2e 2f 2e  |alization...../.|\n 0008c660  2e 2f 73 72 63 2f 6c 69  62 63 61 6d 65 72 61 2f  |./src/libcamera/|\n\nI'll drop this patch.\n\n> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>\n> \n> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>\n> \n> > ---\n> >  meson.build               |  1 +\n> >  src/libcamera/meson.build |  2 +-\n> >  src/meson.build           | 17 +++++++++++++++++\n> >  3 files changed, 19 insertions(+), 1 deletion(-)\n> > \n> > diff --git a/meson.build b/meson.build\n> > index c6e6a934e54e..a1e455249b0d 100644\n> > --- a/meson.build\n> > +++ b/meson.build\n> > @@ -24,6 +24,7 @@ libcamera_version = libcamera_git_version.split('+')[0]\n> >  , \n> >  # Configure the build environment.\n> >  cc = meson.get_compiler('c')\n> > +cxx = meson.get_compiler('cpp')\n> >  config_h = configuration_data()\n> >  \n> >  if cc.has_header_symbol('execinfo.h', 'backtrace')\n> > diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build\n> > index 1b69bc0dee54..ac6f597c6188 100644\n> > --- a/src/libcamera/meson.build\n> > +++ b/src/libcamera/meson.build\n> > @@ -93,7 +93,7 @@ version_cpp = vcs_tag(command : [gen_version, meson.build_root()],\n> >  libcamera_sources += version_cpp\n> >  \n> >  libcamera_deps = [\n> > -    cc.find_library('atomic', required: false),\n> > +    libatomic_dep,\n> >      cc.find_library('dl'),\n> >      libudev,\n> >      dependency('threads'),\n> > diff --git a/src/meson.build b/src/meson.build\n> > index d818d8b86d93..abf755936f2b 100644\n> > --- a/src/meson.build\n> > +++ b/src/meson.build\n> \n> Hrm ... is this the right place for this?\n> \n> I guess it's not a 'bad' place for it.\n> Our top level meson.build is getting busier and busier... and this\n> presumably affects only 'src' code (hence being under src) ... but then\n> 'test/' misses out?\n> \n> Still I guess test/ may be less likely to use atomics...\n\ntest/meson.build is included after src/meson.build, so libatomic_dep is\navailable for it.\n\n> > @@ -1,3 +1,20 @@\n> > +# On some platforms gcc doesn't provide built-ins for atomic operations,\n> > +# explicit linking against libatomic is required.\n> > +if cxx.links('''\n> > +    #include <atomic>\n> > +    #include <cstdint>\n> > +    int main(void)\n> > +    {\n> > +        std::atomic<std::uint32_t> u32(0);\n> > +        std::atomic<std::uint64_t> u64(0);\n> > +        return u32.load() + u64.load();\n> > +    }\n> > +''')\n> > +    libatomic_dep = dependency('', required : false)\n> > +else\n> > +    libatomic_dep = cc.find_library('atomic')\n> > +endif\n> > +\n> >  if get_option('android')\n> >      subdir('android')\n> >  endif","headers":{"Return-Path":"<laurent.pinchart@ideasonboard.com>","Received":["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 55E9960424\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tSun,  8 Mar 2020 00:27:18 +0100 (CET)","from pendragon.ideasonboard.com (81-175-216-236.bb.dnainternet.fi\n\t[81.175.216.236])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id B82775F;\n\tSun,  8 Mar 2020 00:27:17 +0100 (CET)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1583623637;\n\tbh=gx9WY680u3LcTd5J//e4STEd8bcI4iaLTKb11+SiMUk=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=hG/aYkxGC7V/abRAQ1/kXl+RmAMrDP/e5tefVySaknqJWbck1WErV3PFZADUCidJD\n\t73yI4+ipo1piL+oUuhs4Cho2xbGIL/C/LiZSZJDSJzujvXhP87spFr+14rM7W3fEFq\n\tDSyyiXJKCHFmYcj4ZkHlnYJNBT2oytK3eeOkT/aQ=","Date":"Sun, 8 Mar 2020 01:27:14 +0200","From":"Laurent Pinchart <laurent.pinchart@ideasonboard.com>","To":"Kieran Bingham <kieran.bingham@ideasonboard.com>","Cc":"libcamera-devel@lists.libcamera.org","Message-ID":"<20200307232714.GB31018@pendragon.ideasonboard.com>","References":"<20200307211326.26994-1-laurent.pinchart@ideasonboard.com>\n\t<20200307211326.26994-5-laurent.pinchart@ideasonboard.com>\n\t<38b5b232-af04-5759-3bf9-60cf38880f74@ideasonboard.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<38b5b232-af04-5759-3bf9-60cf38880f74@ideasonboard.com>","User-Agent":"Mutt/1.10.1 (2018-07-13)","Subject":"Re: [libcamera-devel] [PATCH v3 4/7] libcamera: Don't unnecessarily\n\tlink against libatomic","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"<libcamera-devel.lists.libcamera.org>","List-Unsubscribe":"<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>","List-Archive":"<https://lists.libcamera.org/pipermail/libcamera-devel/>","List-Post":"<mailto:libcamera-devel@lists.libcamera.org>","List-Help":"<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>","List-Subscribe":"<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>","X-List-Received-Date":"Sat, 07 Mar 2020 23:27:18 -0000"}},{"id":4000,"web_url":"https://patchwork.libcamera.org/comment/4000/","msgid":"<20200307233100.GC31018@pendragon.ideasonboard.com>","date":"2020-03-07T23:31:00","subject":"Re: [libcamera-devel] [PATCH v3 4/7] libcamera: Don't unnecessarily\n\tlink against libatomic","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Kieran,\n\nOn Sun, Mar 08, 2020 at 01:27:14AM +0200, Laurent Pinchart wrote:\n> On Sat, Mar 07, 2020 at 11:01:06PM +0000, Kieran Bingham wrote:\n> > On 07/03/2020 21:13, Laurent Pinchart wrote:\n> > > libatomic provides atomic operations that are also available as compiler\n> > > built-ins on most platforms. On some platforms (such as Sparc) linking\n> > > against libatomic is required to use any atomic operation. libcamera\n> > > links against libatomic if available for that reason.\n> > > \n> > > This however makes libcamera link against libatomic even when not\n> > > required, if libatomic is available. Restrict this to only the cases\n> > > where libatomic is required with a link test.\n> > \n> > Hrm, I thought we discussed and researched this topic when it went in.\n> > \n> > I thought I recalled testing this and identifying that even if libatomic\n> > was found on the system, and would be available to link - The toolchain\n> > would take the internals as a preference and caused no binary change in\n> > the output.\n> > \n> > But I won't overly object to this change though.\n> \n> You're right, I checked again:\n> \n> --- libcamera.so.1.hex  2020-03-08 01:25:05.609314371 +0200\n> +++ libcamera.so.2.hex  2020-03-08 01:25:13.060315088 +0200\n> @@ -35886,7 +35886,7 @@\n>  0008c600  6f 6e 00 00 4d 61 6e 75  61 6c 45 78 70 6f 73 75  |on..ManualExposu|\n>  0008c610  72 65 00 00 4d 61 6e 75  61 6c 47 61 69 6e 00 00  |re..ManualGain..|\n>  0008c620  4c 6f 63 61 74 69 6f 6e  00 00 00 00 76 30 2e 30  |Location....v0.0|\n> -0008c630  2e 30 2b 31 31 31 36 2d  38 36 32 33 31 38 36 38  |.0+1116-86231868|\n> +0008c630  2e 30 2b 31 31 31 37 2d  33 63 36 37 62 33 34 34  |.0+1117-3c67b344|\n>  0008c640  00 00 00 00 42 75 66 66  65 72 00 00 53 65 72 69  |....Buffer..Seri|\n>  0008c650  61 6c 69 7a 61 74 69 6f  6e 00 00 00 2e 2e 2f 2e  |alization...../.|\n>  0008c660  2e 2f 73 72 63 2f 6c 69  62 63 61 6d 65 72 61 2f  |./src/libcamera/|\n> \n> I'll drop this patch.\n\nBy the way I got the idea from\nhttps://gitlab.freedesktop.org/drm/igt-gpu-tools/-/commit/70303d211886ae109dfc0a88948c362359bdd07c.\nI wonder if it means they're doing it wrong too.\n\n> > > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>\n> > \n> > Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>\n> > \n> > > ---\n> > >  meson.build               |  1 +\n> > >  src/libcamera/meson.build |  2 +-\n> > >  src/meson.build           | 17 +++++++++++++++++\n> > >  3 files changed, 19 insertions(+), 1 deletion(-)\n> > > \n> > > diff --git a/meson.build b/meson.build\n> > > index c6e6a934e54e..a1e455249b0d 100644\n> > > --- a/meson.build\n> > > +++ b/meson.build\n> > > @@ -24,6 +24,7 @@ libcamera_version = libcamera_git_version.split('+')[0]\n> > >  , \n> > >  # Configure the build environment.\n> > >  cc = meson.get_compiler('c')\n> > > +cxx = meson.get_compiler('cpp')\n> > >  config_h = configuration_data()\n> > >  \n> > >  if cc.has_header_symbol('execinfo.h', 'backtrace')\n> > > diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build\n> > > index 1b69bc0dee54..ac6f597c6188 100644\n> > > --- a/src/libcamera/meson.build\n> > > +++ b/src/libcamera/meson.build\n> > > @@ -93,7 +93,7 @@ version_cpp = vcs_tag(command : [gen_version, meson.build_root()],\n> > >  libcamera_sources += version_cpp\n> > >  \n> > >  libcamera_deps = [\n> > > -    cc.find_library('atomic', required: false),\n> > > +    libatomic_dep,\n> > >      cc.find_library('dl'),\n> > >      libudev,\n> > >      dependency('threads'),\n> > > diff --git a/src/meson.build b/src/meson.build\n> > > index d818d8b86d93..abf755936f2b 100644\n> > > --- a/src/meson.build\n> > > +++ b/src/meson.build\n> > \n> > Hrm ... is this the right place for this?\n> > \n> > I guess it's not a 'bad' place for it.\n> > Our top level meson.build is getting busier and busier... and this\n> > presumably affects only 'src' code (hence being under src) ... but then\n> > 'test/' misses out?\n> > \n> > Still I guess test/ may be less likely to use atomics...\n> \n> test/meson.build is included after src/meson.build, so libatomic_dep is\n> available for it.\n> \n> > > @@ -1,3 +1,20 @@\n> > > +# On some platforms gcc doesn't provide built-ins for atomic operations,\n> > > +# explicit linking against libatomic is required.\n> > > +if cxx.links('''\n> > > +    #include <atomic>\n> > > +    #include <cstdint>\n> > > +    int main(void)\n> > > +    {\n> > > +        std::atomic<std::uint32_t> u32(0);\n> > > +        std::atomic<std::uint64_t> u64(0);\n> > > +        return u32.load() + u64.load();\n> > > +    }\n> > > +''')\n> > > +    libatomic_dep = dependency('', required : false)\n> > > +else\n> > > +    libatomic_dep = cc.find_library('atomic')\n> > > +endif\n> > > +\n> > >  if get_option('android')\n> > >      subdir('android')\n> > >  endif","headers":{"Return-Path":"<laurent.pinchart@ideasonboard.com>","Received":["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 906C960424\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tSun,  8 Mar 2020 00:31:03 +0100 (CET)","from pendragon.ideasonboard.com (81-175-216-236.bb.dnainternet.fi\n\t[81.175.216.236])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 09F8B5F;\n\tSun,  8 Mar 2020 00:31:02 +0100 (CET)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1583623863;\n\tbh=y2u3XcIJ0jpudxk3n0G0DgXNYVz9FVA3233gUWsFJk0=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=T01npN4ptgU7nWAaKd4pXib3EA1HvMsZmzWoiwvkR8Qm8I46zpaC+tpUiUbjA4/jc\n\tiUPnGDft659nKZC13UkKuyzqxaobJ3Rua1qsg24fwGjvjDHTT+TwKrsIJj4wpI8aPA\n\tIWr2hxf3XogT8B3Wwz/WEQffBy6LlzX88JPicsSk=","Date":"Sun, 8 Mar 2020 01:31:00 +0200","From":"Laurent Pinchart <laurent.pinchart@ideasonboard.com>","To":"Kieran Bingham <kieran.bingham@ideasonboard.com>","Cc":"libcamera-devel@lists.libcamera.org","Message-ID":"<20200307233100.GC31018@pendragon.ideasonboard.com>","References":"<20200307211326.26994-1-laurent.pinchart@ideasonboard.com>\n\t<20200307211326.26994-5-laurent.pinchart@ideasonboard.com>\n\t<38b5b232-af04-5759-3bf9-60cf38880f74@ideasonboard.com>\n\t<20200307232714.GB31018@pendragon.ideasonboard.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<20200307232714.GB31018@pendragon.ideasonboard.com>","User-Agent":"Mutt/1.10.1 (2018-07-13)","Subject":"Re: [libcamera-devel] [PATCH v3 4/7] libcamera: Don't unnecessarily\n\tlink against libatomic","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"<libcamera-devel.lists.libcamera.org>","List-Unsubscribe":"<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>","List-Archive":"<https://lists.libcamera.org/pipermail/libcamera-devel/>","List-Post":"<mailto:libcamera-devel@lists.libcamera.org>","List-Help":"<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>","List-Subscribe":"<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>","X-List-Received-Date":"Sat, 07 Mar 2020 23:31:03 -0000"}}]