Don't fail on libpq-generated error reports in ecpg_raise_backend().

An error PGresult generated by libpq itself, such as a report of
connection loss, won't have broken-down error fields.
ecpg_raise_backend() blithely assumed that PG_DIAG_MESSAGE_PRIMARY
would always be present, and would end up passing a NULL string
pointer to snprintf when it isn't.  That would typically crash
before 3779ac62d, and it would fail to provide a useful error report
in any case.  Best practice is to substitute PQerrorMessage(conn)
in such cases, so do that.

Per bug #17421 from Masayuki Hirose.  Back-patch to all supported
branches.

Discussion: https://postgr.es/m/17421-790ff887e3188874@postgresql.org

diff --git a/src/interfaces/ecpg/ecpglib/error.c b/src/interfaces/ecpg/ecpglib/error.c
index cd6c6a6819bfa5401e1fe438c7d1a07ae4621fdf..26fdcdb69e901ab5ee91c4a752a98b74c98e9a9d 100644 (file)
--- a/src/interfaces/ecpg/ecpglib/error.c
+++ b/src/interfaces/ecpg/ecpglib/error.c
@@ -229,18 +229,17 @@ ecpg_raise_backend(int line, PGresult *result, PGconn *conn, int compat)
        return;
    }
 
-   if (result)
-   {
-       sqlstate = PQresultErrorField(result, PG_DIAG_SQLSTATE);
-       if (sqlstate == NULL)
-           sqlstate = ECPG_SQLSTATE_ECPG_INTERNAL_ERROR;
-       message = PQresultErrorField(result, PG_DIAG_MESSAGE_PRIMARY);
-   }
-   else
-   {
+   /*
+    * PQresultErrorField will return NULL if "result" is NULL, or if there is
+    * no such field, which will happen for libpq-generated errors.  Fall back
+    * to PQerrorMessage in such cases.
+    */
+   sqlstate = PQresultErrorField(result, PG_DIAG_SQLSTATE);
+   if (sqlstate == NULL)
        sqlstate = ECPG_SQLSTATE_ECPG_INTERNAL_ERROR;
+   message = PQresultErrorField(result, PG_DIAG_MESSAGE_PRIMARY);
+   if (message == NULL)
        message = PQerrorMessage(conn);
-   }
 
    if (strcmp(sqlstate, ECPG_SQLSTATE_ECPG_INTERNAL_ERROR) == 0)
    {