[pushed] .gdb_index writer: close the file before unlinking it (Re: [pushed] Re: [PATCH 1/6] Code cleanup: C++ify .gdb_index producer.)

[Pedro Alves <palves at redhat dot com>]

On 06/18/2017 04:11 PM, Eli Zaretskii wrote:
>> Date: Sun, 18 Jun 2017 16:25:30 +0200
>> From: Jan Kratochvil <jan.kratochvil@redhat.com>
>> Cc: gdb-patches@sourceware.org, Victor Leschuk <vleschuk@accesssoftek.com>
>>
>> On Mon, 12 Jun 2017 18:08:07 +0200, Pedro Alves wrote:
>>> +  file_closer close_out_file (out_file);
>>> +  gdb::unlinker unlink_file (filename.c_str ());
>>
>> I heard on MS-Windows one cannot delete a file which is still open.
> 
> Depends on how it was open, but yeah, in general you are right.  (Most
> programs, especially those which were ported from Posix systems, open
> files in a way that indeed precludes their deletion, because that's
> what the MS implementation of 'open' does.)

Yeah, I forgot/missed that here.

I've pushed this in to fix it.

>From 16b7a7199881fa26fc863279bbf08741e5674b5d Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Mon, 19 Jun 2017 12:46:47 +0100
Subject: [PATCH] .gdb_index writer: close the file before unlinking it

We should close the file before unlinking because on MS-Windows one
cannot delete a file that is still open.

I considered making 'gdb::unlinker::unlinker(const char *)'
'noexcept(true)' and then adding
  static_assert (noexcept (gdb::unlinker (filename.c_str ())), "");

but that doesn't really work because gdb::unlinker has a gdb_assert,
which can throw a QUIT if/when the assertion fails.  'noexcept(true)'
would cause GDB to abruptly terminate if/when the assertion fails.

gdb/ChangeLog:
2017-06-19  Pedro Alves  <palves@redhat.com>

	* dwarf2read.c (write_psymtabs_to_index): Construct file_closer
	after gdb::unlinker.
---
 gdb/ChangeLog    | 5 +++++
 gdb/dwarf2read.c | 6 +++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index aaf4b89..c7cf410 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2017-06-19  Pedro Alves  <palves@redhat.com>
+
+	* dwarf2read.c (write_psymtabs_to_index): Construct file_closer
+	after gdb::unlinker.
+
 2017-06-19  Sergio Durigan Junior  <sergiodj@redhat.com>
 
 	* mi/mi-cm-env.c (_initialize_mi_cmd_env): Use getenv instead of
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index abe14b2..2369d4b 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -23776,8 +23776,12 @@ write_psymtabs_to_index (struct objfile *objfile, const char *dir)
   if (!out_file)
     error (_("Can't open `%s' for writing"), filename.c_str ());
 
-  file_closer close_out_file (out_file);
+  /* Order matters here; we want FILE to be closed before FILENAME is
+     unlinked, because on MS-Windows one cannot delete a file that is
+     still open.  (Don't call anything here that might throw until
+     file_closer is created.)  */
   gdb::unlinker unlink_file (filename.c_str ());
+  file_closer close_out_file (out_file);
 
   mapped_symtab symtab;
   data_buf cu_list;
-- 
2.5.5