Problem building libstdc++ for the avr target

[Vladimir V]

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.
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.
>>
>>
>>
-------------- next part --------------
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