res_odbc: fix missing SQL error diagnostic

On SQL error there is not diagnostic information about this error.
There is only
WARNING res_odbc.c: SQL Execute error -1!

The function ast_odbc_print_errors calls a SQLGetDiagField to get the number
of available diagnostic records, but the SQLGetDiagField returns 0.
However SQLGetDiagRec could return one diagnostic records in this case.

Looking at many example of getting diagnostics error information
I found out that the best way it's to use only SQLGetDiagRec
while it returns SQL_SUCCESS.

Also this patch adds calls of ast_odbc_print_errors on SQL_ERROR
to res_config_odbc.

ASTERISK-28065 #close

Change-Id: Iba5ae5470ac49ecd911dd084effbe9efac68ccc1

res/res_config_odbc.c

@@ -116,6 +116,9 @@ static SQLHSTMT custom_prepare(struct odbc_obj *obj, void *data)
 
 	res = SQLPrepare(stmt, (unsigned char *)cps->sql, SQL_NTS);
 	if ((res != SQL_SUCCESS) && (res != SQL_SUCCESS_WITH_INFO)) {
+		if (res == SQL_ERROR) {
+			ast_odbc_print_errors(SQL_HANDLE_STMT, stmt, "SQL Prepare");
+		}
 		ast_log(LOG_WARNING, "SQL Prepare failed! [%s]\n", cps->sql);
 		SQLFreeHandle (SQL_HANDLE_STMT, stmt);
 		return NULL;
@@ -631,6 +634,9 @@ static SQLHSTMT update2_prepare(struct odbc_obj *obj, void *data)
 
 	res = SQLPrepare(stmt, (unsigned char *)ast_str_buffer(sql), SQL_NTS);
 	if ((res != SQL_SUCCESS) && (res != SQL_SUCCESS_WITH_INFO)) {
+		if (res == SQL_ERROR) {
+			ast_odbc_print_errors(SQL_HANDLE_STMT, stmt, "SQL Prepare");
+		}
 		ast_log(LOG_WARNING, "SQL Prepare failed! [%s]\n", ast_str_buffer(sql));
 		SQLFreeHandle(SQL_HANDLE_STMT, stmt);
 		return NULL;

res/res_odbc.c

@@ -431,23 +431,20 @@ struct ast_str *ast_odbc_print_errors(SQLSMALLINT handle_type, SQLHANDLE handle,
 {
 	struct ast_str *errors = ast_str_thread_get(&errors_buf, 16);
 	SQLINTEGER nativeerror = 0;
-	SQLINTEGER numfields = 0;
 	SQLSMALLINT diagbytes = 0;
 	SQLSMALLINT i;
 	unsigned char state[10];
 	unsigned char diagnostic[256];
 
 	ast_str_reset(errors);
-	SQLGetDiagField(handle_type, handle, 1, SQL_DIAG_NUMBER, &numfields,
-			SQL_IS_INTEGER, &diagbytes);
-	for (i = 0; i < numfields; i++) {
-		SQLGetDiagRec(handle_type, handle, i + 1, state, &nativeerror,
-				diagnostic, sizeof(diagnostic), &diagbytes);
+	i = 0;
+	while (SQLGetDiagRec(handle_type, handle, ++i, state, &nativeerror,
+		diagnostic, sizeof(diagnostic), &diagbytes) == SQL_SUCCESS) {
 		ast_str_append(&errors, 0, "%s%s", ast_str_strlen(errors) ? "," : "", state);
 		ast_log(LOG_WARNING, "%s returned an error: %s: %s\n", operation, state, diagnostic);
 		/* XXX Why is this here? */
 		if (i > 10) {
-			ast_log(LOG_WARNING, "Oh, that was good.  There are really %d diagnostics?\n", (int)numfields);
+			ast_log(LOG_WARNING, "There are more than 10 diagnostic records! Ignore the rest.\n");
 			break;
 		}
 	}