[01/10] Add handle_eintr to wrap EINTR handling in syscalls

Message ID 20200902175926.13182-2-n54@gmx.com
State Superseded
Headers show
Series
  • Add minimal NetBSD/amd64 gdbserver support
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Commit Message

Kamil Rytarowski Sept. 2, 2020, 5:59 p.m.
gdbsupport/ChangeLog:

	* eintr.h: Add handle_eintr.
---
 gdbsupport/ChangeLog |  4 ++++
 gdbsupport/eintr.h   | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 gdbsupport/eintr.h

--
2.28.0

Comments

Tom Tromey Sept. 3, 2020, 2:17 p.m. | #1
>>>>> "Kamil" == Kamil Rytarowski <n54@gmx.com> writes:


Kamil> +2020-03-17  Kamil Rytarowski  <n54@gmx.com>
Kamil> +
Kamil> +	* eintr.h: Add handle_eintr.

Kamil> +template <typename Fun, typename... Args>
Kamil> +inline decltype (auto) handle_eintr (const Fun &F, const Args &... A)

I like this, but from what I read it seems that "decltype(auto)" is
C++14 -- but gdb is still C++11.


Kamil> +{
Kamil> +  decltype (F (A...)) ret;
Kamil> +  do
Kamil> +    {
Kamil> +      errno = 0;
Kamil> +      ret = F (A...);
Kamil> +    }
Kamil> +  while (ret == -1 && errno == EINTR);

Also this seems to assume that "ret" is comparable to an int anyway.
So maybe just assuming int everywhere would be ok.

Tom
Kamil Rytarowski Sept. 3, 2020, 9:10 p.m. | #2
On 03.09.2020 16:17, Tom Tromey wrote:
>>>>>> "Kamil" == Kamil Rytarowski <n54@gmx.com> writes:

> 

> Kamil> +2020-03-17  Kamil Rytarowski  <n54@gmx.com>

> Kamil> +

> Kamil> +	* eintr.h: Add handle_eintr.

> 

> Kamil> +template <typename Fun, typename... Args>

> Kamil> +inline decltype (auto) handle_eintr (const Fun &F, const Args &... A)

> 

> I like this, but from what I read it seems that "decltype(auto)" is

> C++14 -- but gdb is still C++11.

> 


OK, I have downgraded this to C++11.

> 

> Kamil> +{

> Kamil> +  decltype (F (A...)) ret;

> Kamil> +  do

> Kamil> +    {

> Kamil> +      errno = 0;

> Kamil> +      ret = F (A...);

> Kamil> +    }

> Kamil> +  while (ret == -1 && errno == EINTR);

> 

> Also this seems to assume that "ret" is comparable to an int anyway.

> So maybe just assuming int everywhere would be ok.

> 


This assumption is not always valid, e.g. read(2) returns ssize_t.

I've added in the template flexibility of the returned type as it could
be e.g. nullptr for fopen(3).

> Tom

>

Patch

diff --git a/gdbsupport/ChangeLog b/gdbsupport/ChangeLog
index a1960537384..7a429367941 100644
--- a/gdbsupport/ChangeLog
+++ b/gdbsupport/ChangeLog
@@ -1,3 +1,7 @@ 
+2020-03-17  Kamil Rytarowski  <n54@gmx.com>
+
+	* eintr.h: Add handle_eintr.
+
 2020-08-13  Simon Marchi  <simon.marchi@polymtl.ca>

 	* selftest.h (run_tests): Change parameter to array_view.
diff --git a/gdbsupport/eintr.h b/gdbsupport/eintr.h
new file mode 100644
index 00000000000..cb35d2ffc3d
--- /dev/null
+++ b/gdbsupport/eintr.h
@@ -0,0 +1,41 @@ 
+/* Utility for handling interrupted syscalls by signals.
+
+   Copyright (C) 2020 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_EINTR_H
+#define GDBSUPPORT_EINTR_H
+
+#include <cerrno>
+
+namespace gdb
+{
+template <typename Fun, typename... Args>
+inline decltype (auto) handle_eintr (const Fun &F, const Args &... A)
+{
+  decltype (F (A...)) ret;
+  do
+    {
+      errno = 0;
+      ret = F (A...);
+    }
+  while (ret == -1 && errno == EINTR);
+  return ret;
+}
+}
+
+#endif /* GDBSUPPORT_EINTR_H */