Restore old pgwin32_message_to_UTF16() behavior outside transactions.

Commit 49c817eab78c6f0ce8c3bf46766b73d6cf3190b7 replaced with a hard
error the dubious pg_do_encoding_conversion() behavior when outside a
transaction.  Reintroduce the historic soft failure locally within
pgwin32_message_to_UTF16().  This fixes errors when writing messages in
less-common encodings to the Windows event log or console.  Back-patch
to 9.4, where the aforementioned commit first appeared.

Per bug #13427 from Dmitri Bourlatchkov.

diff --git a/src/backend/utils/mb/mbutils.c b/src/backend/utils/mb/mbutils.c
index 1e9a004b0d73e21b4fc0f70789e9ad36bd29bdc5..2a8271ab0725042f163b3907c278dfff9c32f327 100644 (file)
--- a/src/backend/utils/mb/mbutils.c
+++ b/src/backend/utils/mb/mbutils.c
@@ -1063,7 +1063,8 @@ pgwin32_message_to_UTF16(const char *str, int len, int *utf16len)
 
    /*
     * Use MultiByteToWideChar directly if there is a corresponding codepage,
-    * or double conversion through UTF8 if not.
+    * or double conversion through UTF8 if not.  Double conversion is needed,
+    * for example, in an ENCODING=LATIN8, LC_CTYPE=C database.
     */
    if (codepage != 0)
    {
@@ -1075,12 +1076,21 @@ pgwin32_message_to_UTF16(const char *str, int len, int *utf16len)
    {
        char       *utf8;
 
-       utf8 = (char *) pg_do_encoding_conversion((unsigned char *) str,
-                                                 len,
-                                                 GetMessageEncoding(),
-                                                 PG_UTF8);
-       if (utf8 != str)
-           len = strlen(utf8);
+       /*
+        * XXX pg_do_encoding_conversion() requires a transaction.  In the
+        * absence of one, hope for the input to be valid UTF8.
+        */
+       if (IsTransactionState())
+       {
+           utf8 = (char *) pg_do_encoding_conversion((unsigned char *) str,
+                                                     len,
+                                                     GetMessageEncoding(),
+                                                     PG_UTF8);
+           if (utf8 != str)
+               len = strlen(utf8);
+       }
+       else
+           utf8 = (char *) str;
 
        utf16 = (WCHAR *) palloc(sizeof(WCHAR) * (len + 1));
        dstlen = MultiByteToWideChar(CP_UTF8, 0, utf8, len, utf16, len);