Add the Release function for TemporaryFiles

Some tests may create a File* by calling fdopen() on the temp file's
fd. We should release the ownership of fd in this case to avoid the
double close.

Bug: 65430057
Test: libbase unit tests pass
Change-Id: I54fcce2029f9a574f53afdbdda737ee58620c73a

base/include/android-base/test_utils.h

@@ -26,6 +26,10 @@ class TemporaryFile {
   TemporaryFile();
   ~TemporaryFile();
 
+  // Release the ownership of fd, caller is reponsible for closing the
+  // fd or stream properly.
+  int release();
+
   int fd;
   char path[1024];
 

base/test_utils.cpp

@@ -85,10 +85,18 @@ TemporaryFile::TemporaryFile() {
 }
 
 TemporaryFile::~TemporaryFile() {
-  close(fd);
+  if (fd != -1) {
+    close(fd);
+  }
   unlink(path);
 }
 
+int TemporaryFile::release() {
+  int result = fd;
+  fd = -1;
+  return result;
+}
+
 void TemporaryFile::init(const std::string& tmp_dir) {
   snprintf(path, sizeof(path), "%s%cTemporaryFile-XXXXXX", tmp_dir.c_str(),
            OS_PATH_SEPARATOR);