[lttng-dev] Building URCU in a Cygwin 64 environment

Wed Jun 1 14:01:50 UTC 2016

Hey Mathieu,

At home (in Cygwin 64), I have a patch for urcu 0.9.2 to fix compilation issues.
This patch is however unrelated to building shared libraries (.dll files) in Cygwin.

Here is a patch (inline and attached) to build shared libraries on Cygwin (the one that you
requested). This patch is based on userspace-rcu 613086f69b4c8e6cc1b73b4e93d6d0497825d1ee.

I tested it on Ubuntu 14.04 ("behavior on non-cygwin builds"), but not on Cygwin as I don't have a Cygwin system at work.

Commands used to test the patch:

git clone https://github.com/urcu/userspace-rcu.git
cd userspace-rcu/
patch -p1 < ~/patches/0001-Port-build-shared-libraries-in-Cygwin.patch 
./bootstrap 
./configure --prefix=$HOME/builds/userspace-rcu/613086f69b4c8e6cc1b73b4e93d6d0497825d1ee/`date -Iseconds`
make -j 4
cd tests/
make check
cd ..
make install

Output of the test:

./run.sh unit_tests
./test_uatomic ................... ok     
./test_urcu_multiflavor .......... ok   
./test_urcu_multiflavor_dynlink .. ok   
All tests successful.
Files=3, Tests=78,  0 wallclock secs ( 0.03 usr  0.00 sys +  0.03 cusr  0.01 csys =  0.07 CPU)
Result: PASS


So, the Result is PASS, which is good.

Tonight, I will combine my 2 patches (the one that enables shared libraries in Cygwin, and the one that fixes various compilation issues in Cygwin)
and send it to the mailing list for review (along with the output of unit tests in Cygwin).

Z1$ cat ~/patches/0001-Port-build-shared-libraries-in-Cygwin.patch 
>From 1b4f39afc781c1a431b9f52adf25aa0856c86142 Mon Sep 17 00:00:00 2001
From: Sebastien Boisvert <sboisvert at gydle.com>
Date: Wed, 1 Jun 2016 09:53:36 -0400
Subject: [PATCH] Port: build shared libraries in Cygwin

Link: https://lists.lttng.org/pipermail/lttng-dev/2016-May/026081.html
Signed-off-by: Sebastien Boisvert <sboisvert at gydle.com>
---
 Makefile.am  | 3 +++
 configure.ac | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/Makefile.am b/Makefile.am
index 672beec..8e25fd9 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -8,6 +8,9 @@ AM_LDFLAGS=-version-info $(URCU_LIBRARY_VERSION)
 if !LIBC_INCLUDES_PTHREAD
 AM_LDFLAGS+=-lpthread
 endif
+if USE_CYGWIN
+AM_LDFLAGS+=-no-undefined
+endif
 AM_CFLAGS=-Wall
 
 SUBDIRS = . doc tests
diff --git a/configure.ac b/configure.ac
index fe1c55d..b3096c6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -134,6 +134,11 @@ AS_CASE([$host],[*-*-linux-androideabi],
 	[AM_CONDITIONAL(TARGET_IS_ANDROID, false)]
 )
 
+AS_CASE([$host],[*-cygwin*],
+	[AM_CONDITIONAL(USE_CYGWIN, true)],
+	[AM_CONDITIONAL(USE_CYGWIN, false)]
+)
+
 AC_SUBST(ARCHTYPE)
 AC_SUBST(SUBARCHTYPE)
 
-- 
1.9.1



On 05/31/2016 05:52 PM, Mathieu Desnoyers wrote:
> ----- On May 31, 2016, at 4:47 PM, Jonathan Rajotte Julien Jonathan.rajotte-julien at efficios.com wrote:
> 
>> Hi Sebastien,
>>
>> I'll simply move the conversation here (from IRC) to have an archive of it.
>>
>> On 2016-05-31 09:39 AM, Sebastien Boisvert wrote:
>>> Hi,
>>>
>>> I am in the process of writing a blog article on the use of the LTTng-UST
>>> userspace event tracer on Windows.
>>>
>>> I am building urcu and LTTng-UST in a Cygwin 64 environment. Then, I plan to use
>>> LTTng in Visual Studio Community, so I mostly need headers (.h) and shared
>>> libraries (.dll).
>>
>> Nice!
>>
>>>
>>> When I am building urcu (0.9.2), I get this message:
>>>
>>> libtool: link: warning: undefined symbols not allowed in x86_64-unknown-cygwin
>>> shared libraries
>>
>> This seems related to a Windows restriction regarding inter-library
>> dependencies [1], the relevant part:
>>
>> "Some platforms, such as Windows, do not even allow you this
>> flexibility. In order to build a shared library, it must be entirely
>> self-contained or it must have dependencies known at link time (that is,
>> have references only to symbols that are found in the .lo files or the
>> specified ‘-l’ libraries), and you need to specify the -no-undefined
>> flag. By default, libtool builds only static libraries on these kinds of
>> platforms."
>>
>> Looks like the -no-undefined might be a good start judging from this
>> patch I found for the urcu cygwin port in yacp [2].
>>
>> Cheers!
>>
>> [1]
>> https://www.gnu.org/software/libtool/manual/libtool.html#Inter_002dlibrary-dependencies
>> [2]
>> https://github.com/fd00/yacp/blob/master/userspace-rcu/userspace-rcu-0.8.7-1bl1.src.patch
> 
> Is there a way we could adapt this patch to urcu upstream without changing
> the behavior on non-cygwin builds ?
> 
> Thanks,
> 
> Mathieu
> 
>>>
>>> The immediate consequence seems to be the absence of .dll files in the urcu
>>> build that I am generating. Otherwise, the build contains static library files
>>> and headers.
>>>
>>> However, I suppose that the .a static library files also have undefined symbols
>>> as I am getting linking issues when building LTTng-UST.
>>>
>>> Do you have a clue of what may be the issue here ? Otherwise, I will continue my
>>> investigation and get around the issue eventually.
>>> _______________________________________________
>>> lttng-dev mailing list
>>> lttng-dev at lists.lttng.org
>>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>
>> --
>> Jonathan R. Julien
>> Efficios
>>
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev at lists.lttng.org
>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> 
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