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GET /api/patches/2227626/?format=api
{ "id": 2227626, "url": "http://patchwork.ozlabs.org/api/patches/2227626/?format=api", "web_url": "http://patchwork.ozlabs.org/project/ubuntu-kernel/patch/20260424025602.71261-2-zixing.liu@canonical.com/", "project": { "id": 15, "url": "http://patchwork.ozlabs.org/api/projects/15/?format=api", "name": "Ubuntu Kernel", "link_name": "ubuntu-kernel", "list_id": "kernel-team.lists.ubuntu.com", "list_email": "kernel-team@lists.ubuntu.com", "web_url": null, "scm_url": null, "webscm_url": null, "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260424025602.71261-2-zixing.liu@canonical.com>", "list_archive_url": null, "date": "2026-04-24T02:56:02", "name": "[SRU,Q,v4,1/1] selftests/powerpc: Suppress -Wmaybe-uninitialized with GCC 15", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "9b9e505195253cd837ef093f0e20e929e3daf234", "submitter": { "id": 90901, "url": "http://patchwork.ozlabs.org/api/people/90901/?format=api", "name": "Zixing Liu", "email": "zixing.liu@canonical.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/ubuntu-kernel/patch/20260424025602.71261-2-zixing.liu@canonical.com/mbox/", "series": [ { "id": 501286, "url": "http://patchwork.ozlabs.org/api/series/501286/?format=api", "web_url": "http://patchwork.ozlabs.org/project/ubuntu-kernel/list/?series=501286", "date": "2026-04-24T02:56:02", "name": "[SRU,Q,v4,1/1] selftests/powerpc: Suppress -Wmaybe-uninitialized with GCC 15", "version": 4, "mbox": "http://patchwork.ozlabs.org/series/501286/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2227626/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2227626/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<kernel-team-bounces@lists.ubuntu.com>", "X-Original-To": "incoming@patchwork.ozlabs.org", "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=fail reason=\"signature verification failed\" (4096-bit key;\n unprotected) header.d=canonical.com header.i=@canonical.com\n header.a=rsa-sha256 header.s=20251003 header.b=Sd7rp1GV;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ubuntu.com\n (client-ip=185.125.189.65; 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charset=\"utf-8\"", "Content-Transfer-Encoding": "base64", "Errors-To": "kernel-team-bounces@lists.ubuntu.com", "Sender": "\"kernel-team\" <kernel-team-bounces@lists.ubuntu.com>" }, "content": "From: Amit Machhiwal <amachhiw@linux.ibm.com>\n\nBugLink: https://bugs.launchpad.net/bugs/2129844\n\nGCC 15 reports the below false positive '-Wmaybe-uninitialized' warning\nin vphn_unpack_associativity() when building the powerpc selftests.\n\n # make -C tools/testing/selftests TARGETS=\"powerpc\"\n [...]\n CC test-vphn\n In file included from test-vphn.c:3:\n In function ‘vphn_unpack_associativity’,\n inlined from ‘test_one’ at test-vphn.c:371:2,\n inlined from ‘test_vphn’ at test-vphn.c:399:9:\n test-vphn.c:10:33: error: ‘be_packed’ may be used uninitialized [-Werror=maybe-uninitialized]\n 10 | #define be16_to_cpup(x) bswap_16(*x)\n | ^~~~~~~~\n vphn.c:42:27: note: in expansion of macro ‘be16_to_cpup’\n 42 | u16 new = be16_to_cpup(field++);\n | ^~~~~~~~~~~~\n In file included from test-vphn.c:19:\n vphn.c: In function ‘test_vphn’:\n vphn.c:27:16: note: ‘be_packed’ declared here\n 27 | __be64 be_packed[VPHN_REGISTER_COUNT];\n | ^~~~~~~~~\n cc1: all warnings being treated as errors\n\nWhen vphn_unpack_associativity() is called from hcall_vphn() in kernel\nthe error is not seen while building vphn.c during kernel compilation.\nThis is because the top level Makefile includes '-fno-strict-aliasing'\nflag always.\n\nThe issue here is that GCC 15 emits '-Wmaybe-uninitialized' due to type\npunning between __be64[] and __b16* when accessing the buffer via\nbe16_to_cpup(). The underlying object is fully initialized but GCC 15\nfails to track the aliasing due to the strict aliasing violation here.\nPlease refer [1] and [2]. This results in a false positive warning which\nis promoted to an error under '-Werror'. This problem is not seen when\nthe compilation is performed with GCC 13 and 14. An issue [1] has also\nbeen created on GCC bugzilla.\n\nThe selftest compiles fine with '-fno-strict-aliasing'. Since this GCC\nflag is used to compile vphn.c in kernel too, the same flag should be\nused to build vphn tests when compiling vphn.c in the selftest as well.\n\nFix this by including '-fno-strict-aliasing' during vphn.c compilation\nin the selftest. This keeps the build working while limiting the scope\nof the suppression to building vphn tests.\n\n[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124427\n[2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99768\n\nFixes: 58dae82843f5 (\"selftests/powerpc: Add test for VPHN\")\nReviewed-by: Vaibhav Jain <vaibhav@linux.ibm.com>\nSigned-off-by: Amit Machhiwal <amachhiw@linux.ibm.com>\nTested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>\nSigned-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>\nLink: https://patch.msgid.link/20260313165426.43259-1-amachhiw@linux.ibm.com\n(cherry picked from commit 6e65886fceb23605eff952d6b1975737b4c4b154)\nSigned-off-by: Zixing Liu <zixing.liu@canonical.com>\n---\n tools/testing/selftests/powerpc/vphn/Makefile | 2 +-\n 1 file changed, 1 insertion(+), 1 deletion(-)", "diff": "diff --git a/tools/testing/selftests/powerpc/vphn/Makefile b/tools/testing/selftests/powerpc/vphn/Makefile\nindex 61d519a076c6..778fc396340d 100644\n--- a/tools/testing/selftests/powerpc/vphn/Makefile\n+++ b/tools/testing/selftests/powerpc/vphn/Makefile\n@@ -5,7 +5,7 @@ top_srcdir = ../../../../..\n include ../../lib.mk\n include ../flags.mk\n \n-CFLAGS += -m64 -I$(CURDIR)\n+CFLAGS += -m64 -I$(CURDIR) -fno-strict-aliasing\n \n $(TEST_GEN_PROGS): ../harness.c\n \n", "prefixes": [ "SRU", "Q", "v4", "1/1" ] }