util: Pre-allocate buffer for ovs_lasterror_to_string().

This lets us call ovs_lasterror_to_string() and not having
to do an extra call of LocalFree() on the returned string.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>

lib/entropy.c

@@ -60,10 +60,8 @@ get_entropy(void *buffer, size_t n)
     CryptAcquireContext(&crypt_prov, NULL, NULL,
                         PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
     if (!CryptGenRandom(crypt_prov, n, buffer)) {
-        char *msg_buf = ovs_lasterror_to_string();
+        VLOG_ERR("CryptGenRandom: read error (%s)", ovs_lasterror_to_string());
         error = EINVAL;
-        VLOG_ERR("CryptGenRandom: read error (%s)", msg_buf);
-        LocalFree(msg_buf);
     }
 
     CryptReleaseContext(crypt_prov, 0);

lib/lockfile.c

@@ -285,9 +285,7 @@ lockfile_try_lock_windows(const char *name, pid_t *pidp,
     retval = LockFileEx(lock_handle, LOCKFILE_EXCLUSIVE_LOCK
                         | LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0, &overl);
     if (!retval) {
-        char *msg_buf = ovs_lasterror_to_string();
-        VLOG_WARN("Failed to lock file : %s", msg_buf);
-        LocalFree(msg_buf);
+        VLOG_WARN("Failed to lock file : %s", ovs_lasterror_to_string());
         return EEXIST;
     }
 

lib/socket-util.c

@@ -65,13 +65,6 @@ VLOG_DEFINE_THIS_MODULE(socket_util);
  * space for a null terminator. */
 #define MAX_UN_LEN (sizeof(((struct sockaddr_un *) 0)->sun_path) - 1)
 
-#ifdef _WIN32
-/* Buffer used by sock_strerror(). */
-DEFINE_STATIC_PER_THREAD_DATA(struct { char s[128]; },
-                              sockerror_buffer,
-                              { "" });
-#endif
-
 static int getsockopt_int(int fd, int level, int option, const char *optname,
                           int *valuep);
 
@@ -1355,21 +1348,15 @@ ss_length(const struct sockaddr_storage *ss)
 
 /* For Windows socket calls, 'errno' is not set.  One has to call
  * WSAGetLastError() to get the error number and then pass it to
- * FormatMessage() (through this function) to get the correct error string.
-
+ * this function to get the correct error string.
+ *
  * ovs_strerror() calls strerror_r() and would not get the correct error
  * string for Windows sockets, but is good for POSIX. */
 const char *
 sock_strerror(int error)
 {
 #ifdef _WIN32
-    enum { BUFSIZE = sizeof sockerror_buffer_get()->s };
-    char *buffer = sockerror_buffer_get()->s;
-
-    FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM
-                  | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, error, 0,
-                  buffer, BUFSIZE, NULL);
-    return buffer;
+    return ovs_format_message(error);
 #else
     return ovs_strerror(error);
 #endif

lib/util.c

@@ -50,7 +50,7 @@ DEFINE_PER_THREAD_MALLOCED_DATA(char *, subprogram_name);
 /* --version option output. */
 static char *program_version;
 
-/* Buffer used by ovs_strerror(). */
+/* Buffer used by ovs_strerror() and ovs_format_message(). */
 DEFINE_STATIC_PER_THREAD_DATA(struct { char s[128]; },
                               strerror_buffer,
                               { "" });
@@ -1666,17 +1666,22 @@ exit:
 
 #ifdef _WIN32
 
-/* Calls FormatMessage() with GetLastError() as an argument. Returns
- * pointer to a buffer that receives the null-terminated string that specifies
- * the formatted message and that has to be freed by the caller with
- * LocalFree(). */
+char *
+ovs_format_message(int error)
+{
+    enum { BUFSIZE = sizeof strerror_buffer_get()->s };
+    char *buffer = strerror_buffer_get()->s;
+
+    FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                  NULL, error, 0, buffer, BUFSIZE, NULL);
+    return buffer;
+}
+
+/* Returns a null-terminated string that explains the last error.
+ * Use this function to get the error string for WINAPI calls. */
 char *
 ovs_lasterror_to_string(void)
 {
-    char *buffer;
-    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM
-                  | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, GetLastError(), 0,
-                  (char *)&buffer, 0, NULL);
-    return buffer;
+    return ovs_format_message(GetLastError());
 }
 #endif

lib/util.h

@@ -491,6 +491,7 @@ uint64_t bitwise_get(const void *src, unsigned int src_len,
 
 #ifdef _WIN32
 
+char *ovs_format_message(int error);
 char *ovs_lasterror_to_string(void);
 #endif