From 28d01b1d69e947a50b9ab9b45113fda1c4f96ac9 Mon Sep 17 00:00:00 2001 From: Chenyi Qiang Date: Thu, 15 Sep 2022 17:10:34 +0800 Subject: [PATCH] configure: Add -Wno-gnu-variable-sized-type-not-at-end MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A Linux headers update to v6.0-rc switches some definitions from GNU 'zero-length-array' extension to the C-standard-defined flexible array member. e.g. struct kvm_msrs { __u32 nmsrs; /* number of msrs in entries */ __u32 pad; - struct kvm_msr_entry entries[0]; + struct kvm_msr_entry entries[]; }; Those (unlike the GNU zero-length-array) have some extra restrictions like 'this must be put at the end of a struct', which clang build would complain about. e.g. the current code struct { struct kvm_msrs info; struct kvm_msr_entry entries[1]; } msr_data = { } generates the warning like: target/i386/kvm/kvm.c:2868:25: error: field 'info' with variable sized type 'struct kvm_msrs' not at the end of a struct or class is a GNU extension [-Werror,-Wgnu-variable-sized-type-not-at-end] struct kvm_msrs info; ^ In fact, the variable length 'entries[]' field in 'info' is zero-sized in GNU defined semantics, which can give predictable offset for 'entries[1]' in local msr_data. The local defined struct is just there to force a stack allocation large enough for 1 kvm_msr_entry, a clever trick but requires to turn off this clang warning. Suggested-by: Daniel P. Berrangé Signed-off-by: Chenyi Qiang Reviewed-by: Richard Henderson Reviewed-by: Cornelia Huck Message-Id: <20220915091035.3897-2-chenyi.qiang@intel.com> Signed-off-by: Thomas Huth --- configure | 1 + 1 file changed, 1 insertion(+) diff --git a/configure b/configure index 0bbf9d28af..78e0ab8db4 100755 --- a/configure +++ b/configure @@ -1258,6 +1258,7 @@ add_to nowarn_flags -Wno-string-plus-int add_to nowarn_flags -Wno-typedef-redefinition add_to nowarn_flags -Wno-tautological-type-limit-compare add_to nowarn_flags -Wno-psabi +add_to nowarn_flags -Wno-gnu-variable-sized-type-not-at-end gcc_flags="$warn_flags $nowarn_flags"