From: Jonathan Wakely <jwakely@redhat.com>
To: Vladimir V <vv.os.swe@gmail.com>
Cc: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: Re: Problem building libstdc++ for the avr target
Date: Wed, 9 Dec 2020 17:01:25 +0000 [thread overview]
Message-ID: <20201209170125.GW2309743@redhat.com> (raw)
In-Reply-To: <20201209124933.GU2309743@redhat.com>
[-- Attachment #1: Type: text/plain, Size: 1736 bytes --]
On 09/12/20 12:49 +0000, Jonathan Wakely wrote:
>On 09/12/20 13:32 +0100, Vladimir V wrote:
>>Hello.
>>
>>While testing with the current upstream I encountered a compilation issue.
>>Although I build with "--disable-threads" flag the following error occurs:
>>
>>../../../../../libstdc++-v3/src/c++11/thread.cc:39:4: error: #error "No
>>sleep function known for this target"
>>
>>Previously the check was inside the #ifdef _GLIBCXX_HAS_GTHREADS that
>>prevented the error from happening (in my case with gcc v10.1),
>>So I would like to ask if the thread.cc should be involved in the build if
>>the threads support is configured to be disabled?
>
>Yes, the file is always built, but which definitions it contains
>depends on what is configured for the target.
>
>The std::this_thread::sleep_for and std::this_thread::sleep_until
>functions don't actually depend on threads at all. They just sleep.
>
>But that still requires target support, just different support from
>threads.
>
>>And if it should, then can the condition be reworked to cover the described
>>case?
>
>Yes, I'll do that. Thanks for bringing it to my attention.
>
>I assume we can't use avr-libc's delay functions, because they depend
>on the CPU clock frequency, which isn't known when we compile
>libstdc++. So I'll just suppress the declarations of those functions
>and remove the #error.
The attached patch adds a new _GLIBCXX_NO_SLEEP configure macro which
should get defined for your hosted AVR build. That should mean that
std::this_thread::sleep_for is not defined, and src/c++11/thread.cc
will no longer insist on some way to sleep being supported.
I've only tested this on powerpc64le-linux, so please let me know if
it works for you.
Pushed to master.
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[-- Type: text/x-patch, Size: 4048 bytes --]
commit 0aa1786d34b891c8e1e219fb11255af5358013c4
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Wed Dec 9 16:53:18 2020
libstdc++: Fix build failure for target with no way to sleep
In previous releases the std::this_thread::sleep_for function was only
declared if the target supports multiple threads. I changed that
recently in r11-2649-g5bbb1f3000c57fd4d95969b30fa0e35be6d54ffb so that
sleep_for could be used single-threaded. But that means that targets
using --disable-threads are now required to provide some way to sleep.
This breaks the build for (at least) AVR when trying to build a hosted
library.
This patch adds a new autoconf macro that is defined when no way to
sleep is available, and uses that to suppress the sleeping functions in
std::this_thread.
The #error in src/c++11/thread.cc is retained for the case where there
is no sleep function available but multiple threads are supported. This
is consistent with previous releases, but that #error could probably be
removed without any consequences.
libstdc++-v3/ChangeLog:
* acinclude.m4 (GLIBCXX_ENABLE_LIBSTDCXX_TIME): Define NO_SLEEP
if none of nanosleep, sleep and Sleep is available.
* config.h.in: Regenerate.
* configure: Regenerate.
* include/std/thread [_GLIBCXX_NO_SLEEP] (__sleep_for): Do
not declare.
[_GLIBCXX_NO_SLEEP] (sleep_for, sleep_until): Do not
define.
* src/c++11/thread.cc [_GLIBCXX_NO_SLEEP] (__sleep_for): Do
not define.
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index fcd9ea3d23a..61191812c92 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -1626,16 +1626,22 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
fi
if test x"$ac_has_nanosleep$ac_has_sleep" = x"nono"; then
+ ac_no_sleep=yes
AC_MSG_CHECKING([for Sleep])
AC_TRY_COMPILE([#include <windows.h>],
[Sleep(1)],
[ac_has_win32_sleep=yes],[ac_has_win32_sleep=no])
if test x"$ac_has_win32_sleep" = x"yes"; then
AC_DEFINE(HAVE_WIN32_SLEEP,1, [Defined if Sleep exists.])
+ ac_no_sleep=no
fi
AC_MSG_RESULT($ac_has_win32_sleep)
fi
+ if test x"$ac_no_sleep" = x"yes"; then
+ AC_DEFINE(NO_SLEEP,1, [Defined if no way to sleep is available.])
+ fi
+
AC_SUBST(GLIBCXX_LIBS)
CXXFLAGS="$ac_save_CXXFLAGS"
diff --git a/libstdc++-v3/include/std/thread b/libstdc++-v3/include/std/thread
index 6ea8a51c0cf..8d0ede2b6c2 100644
--- a/libstdc++-v3/include/std/thread
+++ b/libstdc++-v3/include/std/thread
@@ -122,8 +122,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*/
namespace this_thread
{
+#ifndef _GLIBCXX_NO_SLEEP
+
+#ifndef _GLIBCXX_USE_NANOSLEEP
void
__sleep_for(chrono::seconds, chrono::nanoseconds);
+#endif
/// this_thread::sleep_for
template<typename _Rep, typename _Period>
@@ -168,7 +172,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__now = _Clock::now();
}
}
- }
+ } // namespace this_thread
+#endif // ! NO_SLEEP
#ifdef __cpp_lib_jthread
diff --git a/libstdc++-v3/src/c++11/thread.cc b/libstdc++-v3/src/c++11/thread.cc
index a9c92804959..62f6ddcd802 100644
--- a/libstdc++-v3/src/c++11/thread.cc
+++ b/libstdc++-v3/src/c++11/thread.cc
@@ -35,7 +35,8 @@
# include <unistd.h>
# elif defined(_GLIBCXX_HAVE_WIN32_SLEEP)
# include <windows.h>
-# else
+# elif defined _GLIBCXX_NO_SLEEP && defined _GLIBCXX_HAS_GTHREADS
+// We expect to be able to sleep for targets that support multiple threads:
# error "No sleep function known for this target"
# endif
#endif
@@ -196,6 +197,7 @@ _GLIBCXX_END_NAMESPACE_VERSION
#endif // _GLIBCXX_HAS_GTHREADS
+#ifndef _GLIBCXX_NO_SLEEP
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -252,3 +254,4 @@ namespace this_thread
}
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
+#endif // ! NO_SLEEP
next prev parent reply other threads:[~2020-12-09 17:01 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-07 17:32 Vladimir V
2020-12-07 20:30 ` Jonathan Wakely
2020-12-07 20:32 ` Jonathan Wakely
2020-12-09 0:28 ` Vladimir V
2020-12-09 12:32 ` Vladimir V
2020-12-09 12:49 ` Jonathan Wakely
2020-12-09 17:01 ` Jonathan Wakely [this message]
2020-12-09 23:00 ` Vladimir V
2020-12-10 17:39 ` Vladimir V
2020-12-10 20:15 ` Jonathan Wakely
2020-12-10 20:31 ` Vladimir V
2020-12-15 11:48 ` Jonathan Wakely
2020-12-16 7:33 ` Vladimir V
2020-12-07 20:41 ` Keith Packard
2020-12-07 21:06 ` Jonathan Wakely
2021-01-04 11:28 ` Vladimir V
2021-01-08 18:21 ` Jonathan Wakely
2021-01-22 14:46 ` Vladimir V
2021-02-07 13:55 ` Vladimir V
2021-02-07 18:22 ` Vladimir V
2021-02-07 18:23 ` Keith Packard
2021-02-07 22:33 ` Vladimir V
2021-02-07 23:06 ` Keith Packard
2021-02-08 12:58 ` Vladimir V
2021-02-08 17:38 ` Jonathan Wakely
2021-02-08 17:45 ` Jonathan Wakely
2021-02-08 17:47 ` Jonathan Wakely
2021-02-08 22:25 ` Vladimir V
2021-02-09 10:47 ` Jonathan Wakely
2021-02-09 10:54 ` Vladimir V
2021-03-25 9:27 ` Vladimir V
2021-03-25 12:36 ` Jonathan Wakely
2021-03-25 18:27 ` Jonathan Wakely
2021-03-25 21:37 ` Vladimir V
2021-03-25 23:02 ` Jonathan Wakely
2021-03-26 8:25 ` Vladimir V
2020-12-07 21:51 ` Vladimir V
2020-12-07 23:00 ` Keith Packard
2020-12-08 8:12 ` Vladimir V
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