Re: [PATCH 1/3] gdbsupport: change scoped_fd::to_file to a free function

[Simon Marchi <simon.marchi@polymtl.ca>]

On 2021-07-30 09:47, Tom Tromey wrote:
> Simon> The following patch wants to chagne gdb_fopen_cloexec to return a
> 
> "change"
> Also I think that should be gdb_mkostemp_cloexec?

Both, actually.

> 
> Simon> scoped_fd.  Doing this causes a cyclic include between scoped_fd.h and
> Simon> filestuff.h.  scoped_fd.h includes filestuff.h because of the
> Simon> scoped_fd::to_file method.  To fix that, change scoped_fd::to_file to
> Simon> be a free function in filestuff.h.
> 
> I guess that, while I don't really object, it seems like it would be
> better to break the dependency some other way.  For instance would
> introducing a new header that only declares gdb_file_up work?  The idea
> behind this is not to let the oddities of C++ header file management
> influence how the code itself is spelled -- that seems like a kind of
> inversion to me.  Going along with this is the idea that a method is the
> clearest way to write to_file.  These are all opinions of course, maybe
> there's a reason to prefer a free function.

There's three way to do this:

 - scoped_fd::to_file method
 - gdb_file::from_fd static method
 - a free function

I never know which is best, which object should know about the other
one, or if no object should no about the other (and hence use a free
function).

But I agree with you here.  See the updated 1/3 patch below.

Patch 2 changes trivially to update the includes and a to_file call.


From 7a281de194629ba00546c2d34cc41d2f77ccc5b3 Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@polymtl.ca>
Date: Thu, 22 Jul 2021 11:34:57 -0400
Subject: [PATCH] gdbsupport: move gdb_file_up to its own file

The following patches wants to change gdb_fopen_cloexec and
gdb_mkostemp_cloexec to return a scoped_fd.  Doing this causes a cyclic
include between scoped_fd.h and filestuff.h, that both want to include
each other.  scoped_fd.h includes filestuff.h because of the
scoped_fd::to_file method's return value.  filestuff.h would then
include scoped_fd.h for gdb_fopen_cloexec's and gdb_mkostemp_cloexec's
return values.

To fix that, move gdb_file_up to its own file, gdb_file.h.

Change-Id: Ic82a48914b2aacee8f14af535b7469245f88b93d
---
 gdbsupport/filestuff.h | 13 +------------
 gdbsupport/gdb_file.h  | 37 +++++++++++++++++++++++++++++++++++++
 gdbsupport/scoped_fd.h |  2 +-
 3 files changed, 39 insertions(+), 13 deletions(-)
 create mode 100644 gdbsupport/gdb_file.h

diff --git a/gdbsupport/filestuff.h b/gdbsupport/filestuff.h
index 7f4cfb2388b1..aa15f89aa920 100644
--- a/gdbsupport/filestuff.h
+++ b/gdbsupport/filestuff.h
@@ -21,6 +21,7 @@
 
 #include <dirent.h>
 #include <fcntl.h>
+#include "gdb_file.h"
 
 /* Note all the file descriptors which are open when this is called.
    These file descriptors will not be closed by close_most_fds.  */
@@ -69,18 +70,6 @@ gdb_open_cloexec (const std::string &filename, int flags,
   return gdb_open_cloexec (filename.c_str (), flags, mode);
 }
 
-struct gdb_file_deleter
-{
-  void operator() (FILE *file) const
-  {
-    fclose (file);
-  }
-};
-
-/* A unique pointer to a FILE.  */
-
-typedef std::unique_ptr<FILE, gdb_file_deleter> gdb_file_up;
-
 /* Like 'fopen', but ensures that the returned file descriptor has the
    close-on-exec flag set.  */
 
diff --git a/gdbsupport/gdb_file.h b/gdbsupport/gdb_file.h
new file mode 100644
index 000000000000..2f5b399f6e87
--- /dev/null
+++ b/gdbsupport/gdb_file.h
@@ -0,0 +1,37 @@
+/* gdb_file_up, an RAII wrapper around FILE.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_GDB_FILE
+#define GDBSUPPORT_GDB_FILE
+
+#include <memory>
+#include <stdio.h>
+
+struct gdb_file_deleter
+{
+  void operator() (FILE *file) const
+  {
+    fclose (file);
+  }
+};
+
+/* A unique pointer to a FILE.  */
+
+typedef std::unique_ptr<FILE, gdb_file_deleter> gdb_file_up;
+
+#endif
diff --git a/gdbsupport/scoped_fd.h b/gdbsupport/scoped_fd.h
index a1aad8493998..f16e811a2cef 100644
--- a/gdbsupport/scoped_fd.h
+++ b/gdbsupport/scoped_fd.h
@@ -21,7 +21,7 @@
 #define COMMON_SCOPED_FD_H
 
 #include <unistd.h>
-#include "filestuff.h"
+#include "gdb_file.h"
 
 /* A smart-pointer-like class to automatically close a file descriptor.  */
 
-- 
2.33.0