Fix error handling for negative size in ftruncate.

Bug: 21309901
Change-Id: I54692ab8105dd09db6af7a2c0894a17bdd118aa0
(cherry picked from commit c05554ec5c9aff5e0f1e83de9bb62c3569eecca2)

1 files changed, 28 insertions, 0 deletions

diff --git a/libc/bionic/ftruncate.cpp b/libc/bionic/ftruncate.cpp
new file mode 100644
index 0000000..c073f2d
--- /dev/null
+++ b/libc/bionic/ftruncate.cpp
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <sys/cdefs.h>
+#include <unistd.h>
+
+#if !defined(__USE_FILE_OFFSET64) && !defined(__LP64__)
+// The kernel's implementation of ftruncate uses an unsigned long for the length
+// parameter, so it will not catch negative values. On the other hand
+// ftruncate64 does check for this, so just forward the call.
+int ftruncate(int filedes, off_t length) {
+  return ftruncate64(filedes, length);
+}
+#endif