fix(mysql): restore bind buffer length for newer mariadb versions

Author: simonz

diesel/src/mysql/connection/stmt/mod.rs

@@ -117,7 +117,14 @@ impl Statement {
     /// you must call this function again before calling `mysql_stmt_fetch`.
     pub unsafe fn bind_result(&self, binds: *mut ffi::MYSQL_BIND) -> QueryResult<()> {
         unsafe {
+            let prev_length = *(*binds).length;
             ffi::mysql_stmt_bind_result(self.stmt.as_ptr(), binds);
+
+            // HACK: Newer libmariadb versions initialise length to 0 for fixed-size
+            // types. Restore length to previous value if this is the case.
+            if *(*binds).length == 0 {
+                *(*binds).length = prev_length;
+            }
         }
         self.did_an_error_occur()
     }
@@ -178,7 +185,19 @@ impl StatementUse<'_> {
     }
 
     pub(super) fn populate_row_buffers(&self, binds: &mut OutputBinds) -> QueryResult<Option<()>> {
-        let next_row_result = unsafe { ffi::mysql_stmt_fetch(self.inner.stmt.as_ptr()) };
+        let next_row_result = unsafe {
+            let prev_length = *(*(*self.inner.stmt.as_ptr()).bind).length;
+            let result = ffi::mysql_stmt_fetch(self.inner.stmt.as_ptr());
+
+            // HACK: Newer libmariadb versions initialise length to 0 for fixed-size
+            // types. Restore length to previous value if this is the case.
+            if *(*(*self.inner.stmt.as_ptr()).bind).length == 0 {
+                *(*(*self.inner.stmt.as_ptr()).bind).length = prev_length;
+            }
+
+            result
+        };
+
         if next_row_result < 0 {
             self.inner.did_an_error_occur().map(Some)
         } else {