Re: Problem building libstdc++ for the avr target

Re: Problem building libstdc++ for the avr target

[Jonathan Wakely]

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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.



[-- Attachment #2: patch.txt --]
[-- 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

Re: Problem building libstdc++ for the avr target

[Vladimir V]

Thank you for the quick response.
The patch solves the problem.

ср, 9 дек. 2020 г. в 18:01, Jonathan Wakely <jwakely@redhat.com>:

> 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.
>
>
>

Re: Problem building libstdc++ for the avr target

[Jonathan Wakely]

On 10/12/20 18:39 +0100, Vladimir V via Libstdc++ wrote:
>Hello.
>
>Could you please have a look at my trivial patch.
>It works as intended with avr-libc and doesn't seem to introduce
>regressions for x86_64 hosts.

I've pushed this to master now, thanks for the patch.

>What would be your suggestions for testing?
>
>Thank you
>Vladimir
>
>чт, 10 дек. 2020 г. в 00:00, Vladimir V <vv.os.swe@gmail.com>:
>
>> Thank you for the quick response.
>> The patch solves the problem.
>>
>> ср, 9 дек. 2020 г. в 18:01, Jonathan Wakely <jwakely@redhat.com>:
>>
>>> 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.
>>>
>>>
>>>

From fbb2144b56625adf594f8812189b983fa66c910a Mon Sep 17 00:00:00 2001
>From: Vladimir Vishnevsky <vv.os.swe@gmail.com>
>Date: Tue, 8 Dec 2020 21:45:26 +0100
>Subject: [PATCH] Disabling AC_LIBTOOL_DLOPEN check if building with avr-libc
>
>The AC_LIBTOOL_DLOPEN checks were previously disabled for newlib targets.
>The patch applies similar logic to avr-libc based builds.
>
>2020-12-08 Vladimir Vishnevsky <vv.os.swe@gmail.com>
>
>libstdc++-v3/ChangeLog:
>        Disabling AC_LIBTOOL_DLOPEN check if building with avr-libc.
>        * configure.ac: Skip AC_LIBTOOL_DLOPEN check if avr-libc is used.
>        * configure: Regenerate.
>---
> libstdc++-v3/configure.ac | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
>index cbfdf4c6bad..771814110a1 100644
>--- a/libstdc++-v3/configure.ac
>+++ b/libstdc++-v3/configure.ac
>@@ -90,7 +90,7 @@ AC_SYS_LARGEFILE
> GLIBCXX_CONFIGURE
>
> # Libtool setup.
>-if test "x${with_newlib}" != "xyes"; then
>+if test "x${with_newlib}" != "xyes" && test "x${with_avrlibc}" != "xyes"; then
>   AC_LIBTOOL_DLOPEN
> fi
> AM_PROG_LIBTOOL
>-- 
>2.17.1
>

Re: Problem building libstdc++ for the avr target

[Vladimir V]

Thank you very much.

вт, 15 дек. 2020 г. в 12:48, Jonathan Wakely <jwakely@redhat.com>:

> On 10/12/20 18:39 +0100, Vladimir V via Libstdc++ wrote:
> >Hello.
> >
> >Could you please have a look at my trivial patch.
> >It works as intended with avr-libc and doesn't seem to introduce
> >regressions for x86_64 hosts.
>
> I've pushed this to master now, thanks for the patch.
>
> >What would be your suggestions for testing?
> >
> >Thank you
> >Vladimir
> >
> >чт, 10 дек. 2020 г. в 00:00, Vladimir V <vv.os.swe@gmail.com>:
> >
> >> Thank you for the quick response.
> >> The patch solves the problem.
> >>
> >> ср, 9 дек. 2020 г. в 18:01, Jonathan Wakely <jwakely@redhat.com>:
> >>
> >>> 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.
> >>>
> >>>
> >>>
>
> >From fbb2144b56625adf594f8812189b983fa66c910a Mon Sep 17 00:00:00 2001
> >From: Vladimir Vishnevsky <vv.os.swe@gmail.com>
> >Date: Tue, 8 Dec 2020 21:45:26 +0100
> >Subject: [PATCH] Disabling AC_LIBTOOL_DLOPEN check if building with
> avr-libc
> >
> >The AC_LIBTOOL_DLOPEN checks were previously disabled for newlib targets.
> >The patch applies similar logic to avr-libc based builds.
> >
> >2020-12-08 Vladimir Vishnevsky <vv.os.swe@gmail.com>
> >
> >libstdc++-v3/ChangeLog:
> >        Disabling AC_LIBTOOL_DLOPEN check if building with avr-libc.
> >        * configure.ac: Skip AC_LIBTOOL_DLOPEN check if avr-libc is used.
> >        * configure: Regenerate.
> >---
> > libstdc++-v3/configure.ac | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
> >index cbfdf4c6bad..771814110a1 100644
> >--- a/libstdc++-v3/configure.ac
> >+++ b/libstdc++-v3/configure.ac
> >@@ -90,7 +90,7 @@ AC_SYS_LARGEFILE
> > GLIBCXX_CONFIGURE
> >
> > # Libtool setup.
> >-if test "x${with_newlib}" != "xyes"; then
> >+if test "x${with_newlib}" != "xyes" && test "x${with_avrlibc}" !=
> "xyes"; then
> >   AC_LIBTOOL_DLOPEN
> > fi
> > AM_PROG_LIBTOOL
> >--
> >2.17.1
> >
>
>

Re: Problem building libstdc++ for the avr target

[Jonathan Wakely]

[-- Attachment #1: Type: text/plain, Size: 1970 bytes --]

On 25/03/21 12:36 +0000, Jonathan Wakely wrote:
>On 25/03/21 10:27 +0100, Vladimir V wrote:
>>Hello.
>>
>>Recently I tried the 'freestanding' build of the libstdc++ for the avr to
>>verify that my fixes were sufficient for it as well.
>>Unfortunately, I encountered the following error:
>>../../../../libstdc++-v3/libsupc++/new_opa.cc: In function 'void*
>>__gnu_cxx::aligned_alloc(std::size_t, std::size_t)':
>>../../../../libstdc++-v3/libsupc++/new_opa.cc:97:28: error: 'malloc' was
>>not declared in this scope
>>  97 |   void* const malloc_ptr = malloc(sz + al);
>>
>>My investigation showed that in the chain of includes the stdlib.h of the
>>avr-libc is not present.
>>It looks like includes are resolved in the following way (here are the
>>original paths as they are linked from out folders during build):
>>new_opa.cc -> libstdc++-v3/include/c_compatibility/stdlib.h ->
>>libstdc++-v3/include/c_global/cstdlib
>>In cstdlib, for non-hosted builds stdlib.h is not included.
>>
>>This problem is not present if the non-hosted build is done with
>>'with-newlib' flag instead of 'with-avrlibc' (common workaround as the
>>avrlibc build was fixed only recently).
>>Might it be that some include order depends on the target libc? Or maybe
>>some implicit conditions are involved?
>>
>>Could you please support me with this issue?
>
>I think this is needed:
>
>--- a/libstdc++-v3/libsupc++/new_opa.cc
>+++ b/libstdc++-v3/libsupc++/new_opa.cc
>@@ -54,6 +54,10 @@ extern "C"
>   void *posix_memalign(void **, size_t alignment, size_t size);
> # elif _GLIBCXX_HAVE_MEMALIGN
>   void *memalign(size_t alignment, size_t size);
>+#else
>+  // A freestanding C runtime may not provide "malloc" -- but there is no
>+  // other reasonable way to implement "operator new".
>+  void *malloc (std::size_t);   with GCC 7.5

Oops, there was a stray "with GCC 7.5" that got into my clipboard
there!

I've pushed the attached patch, please test and confirm if it fixes
your problem.



[-- Attachment #2: patch.txt --]
[-- Type: text/x-patch, Size: 1093 bytes --]

commit 15d649f79d6b6dc336f6a32eec242b652a262a82
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Mar 25 18:24:37 2021

    libstdc++: Declare malloc for freestanding
    
    For a target with none of aligned_alloc, memalign etc. we defined our
    own aligned_alloc using malloc, so we need a declaration of malloc. As
    in libsupc++/new_op.cc we need to declare it ourselves for freestanding
    environments.
    
    libstdc++-v3/ChangeLog:
    
            * libsupc++/new_opa.cc [!_GLIBCXX_HOSTED]: Declare malloc.

diff --git a/libstdc++-v3/libsupc++/new_opa.cc b/libstdc++-v3/libsupc++/new_opa.cc
index 59296226e83..6b78729dc24 100644
--- a/libstdc++-v3/libsupc++/new_opa.cc
+++ b/libstdc++-v3/libsupc++/new_opa.cc
@@ -54,6 +54,10 @@ extern "C"
   void *posix_memalign(void **, size_t alignment, size_t size);
 # elif _GLIBCXX_HAVE_MEMALIGN
   void *memalign(size_t alignment, size_t size);
+# else
+  // A freestanding C runtime may not provide "malloc" -- but there is no
+  // other reasonable way to implement "operator new".
+  void *malloc(size_t);
 # endif
 }
 #endif