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Re: [Qemu-block] [Qemu-devel] [PATCH v3 1/9] util: Add UUID API


From: Richard Henderson
Subject: Re: [Qemu-block] [Qemu-devel] [PATCH v3 1/9] util: Add UUID API
Date: Wed, 10 Aug 2016 16:25:56 +0530
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0

On 08/09/2016 12:19 PM, Fam Zheng wrote:
+/* Version 4 UUID (pseudo random numbers), RFC4122 4.4. */
+
+typedef struct {
+    unsigned char data[16];
+} QemuUUID;
...
+void qemu_uuid_generate(QemuUUID *uuid)
+{
+    int i;
+    uint32_t *out = (uint32_t *)&uuid->data[0];

You can't do this cast without adding alignment on the QemuUUID structure.

+    for (i = 0; i < 4; ++i) {
+        out[i] = g_random_int();
+    }

But if there's no other need for uint32_t access to QemuUUID, you could either

(1) write into a local uint32_t[4] array and memcpy over, or
(2) use stl_he_p from qemu/bswap.h, which will handle the unaligned store.


r~



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