This is easily computed by advancing past the structure.
At the same time, replace the magic number "64".

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/i386/signal.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c
index 89048ed069..f8064691c4 100644
--- a/linux-user/i386/signal.c
+++ b/linux-user/i386/signal.c
@@ -67,7 +67,6 @@ struct target_fpstate_fxsave {
     uint32_t xmm_space[64];
     uint32_t hw_reserved[12];
     struct target_fpx_sw_bytes sw_reserved;
-    uint8_t xfeatures[];
 };
 #define TARGET_FXSAVE_SIZE   sizeof(struct target_fpstate_fxsave)
 QEMU_BUILD_BUG_ON(TARGET_FXSAVE_SIZE != 512);
@@ -266,7 +265,7 @@ static void xsave_sigcontext(CPUX86State *env, struct target_fpstate_fxsave *fxs
         assert(!(fxsave_addr & 0x3f));
 
         /* Zero the header, XSAVE *adds* features to an existing save state.  */
-        memset(fxsave->xfeatures, 0, 64);
+        memset(fxsave + 1, 0, sizeof(X86XSaveHeader));
         cpu_x86_xsave(env, fxsave_addr, -1);
         __put_user(TARGET_FP_XSTATE_MAGIC1, &fxsave->sw_reserved.magic1);
         __put_user(extended_size, &fxsave->sw_reserved.extended_size);
-- 
2.34.1