Do not reopen temporary files

The current callers of mkostemp close the file descriptor and then
re-open it with fopen.  It seemed better to me to continue to use the
already-opened file descriptor, so this patch rearranges the code a
little in order to do so.  It takes care to ensure that the files are
only unlinked after the file descriptor in question is closed, as
before.

gdb/ChangeLog
2018-10-27  Tom Tromey  <tom@tromey.com>

	* unittests/scoped_fd-selftests.c (test_to_file): New function.
	(run_tests): Call test_to_file.
	* dwarf-index-write.c (write_psymtabs_to_index): Do not reopen
	temporary files.
	* common/scoped_fd.h (scoped_fd::to_file): New method.

1 files changed, 13 insertions, 0 deletions

diff --git a/gdb/common/scoped_fd.h b/gdb/common/scoped_fd.h
index c2125bd..d20e18a 100644
--- a/gdb/common/scoped_fd.h
+++ b/gdb/common/scoped_fd.h
@@ -21,6 +21,7 @@
 #define SCOPED_FD_H
 
 #include <unistd.h>
+#include "filestuff.h"
 
 /* A smart-pointer-like class to automatically close a file descriptor.  */
 
@@ -43,6 +44,18 @@ public:
     return fd;
   }
 
+  /* Like release, but return a gdb_file_up that owns the file
+     descriptor.  On success, this scoped_fd will be released.  On
+     failure, return NULL and leave this scoped_fd in possession of
+     the fd.  */
+  gdb_file_up to_file (const char *mode) noexcept
+  {
+    gdb_file_up result (fdopen (m_fd, mode));
+    if (result != nullptr)
+      m_fd = -1;
+    return result;
+  }
+
   int get () const noexcept
   {
     return m_fd;