[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
2017-06-19T11:50:56Z

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