[Spice-devel] [PATCH spice-gtk v2 4/4] Add check for macOS, disable ucontext on macOS (deprecated)

[Christophe de Dinechin]

> On 11 May 2017, at 12:56, Daniel P. Berrange <berrange at redhat.com> wrote:
> 
> On Thu, May 11, 2017 at 12:47:08PM +0200, Christophe de Dinechin wrote:
>> From: Christophe de Dinechin <dinechin at redhat.com>
>> 
>> Signed-off-by: Christophe de Dinechin <dinechin at redhat.com>
>> ---
>> configure.ac | 14 ++++++++++++++
>> 1 file changed, 14 insertions(+)
>> 
>> diff --git a/configure.ac b/configure.ac
>> index 74b5811..ecab365 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -62,6 +62,18 @@ esac
>> AC_MSG_RESULT([$os_win32])
>> AM_CONDITIONAL([OS_WIN32],[test "$os_win32" = "yes"])
>> 
>> +AC_MSG_CHECKING([for native macOS])
>> +case "$host_os" in
>> +     *darwin*)
>> +        os_mac=yes
>> +        ;;
>> +     *)
>> +        os_mac=no
>> +        ;;
>> +esac
>> +AC_MSG_RESULT([$os_mac])
>> +AM_CONDITIONAL([OS_MAC],[test "$os_mac" = "yes"])
>> +
>> AC_CHECK_HEADERS([sys/socket.h netinet/in.h arpa/inet.h])
>> AC_CHECK_HEADERS([termios.h])
>> AC_CHECK_HEADERS([epoxy/egl.h],
>> @@ -468,6 +480,8 @@ esac
>> if test "$with_coroutine" = "auto"; then
>>   if test "$os_win32" = "yes"; then
>>     with_coroutine=winfiber
>> +  elif test "$os_mac" = "yes"; then
>> +    with_coroutine=gthread
>>   else
>>     with_coroutine=ucontext
>>   fi
> 
> Despite ucontext being deprecated we are still better off using that &
> ignoring the warnings, than using the gthread impl.

Yes, I remember you explained the benefits of keeping ucontext. But for the moment at least, on macOS, it is not a warning:

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/usr/include/ucontext.h:43:2: error: 
      The deprecated ucontext routines require _XOPEN_SOURCE to be defined
#error The deprecated ucontext routines require _XOPEN_SOURCE to be defined
 ^
1 error generated.

So I can:
- Add the error in the patch description
- Attempt to define _XOPEN_SOURCE in the configuration. I’m concerned about side effects.

The latter leads to another can of worms. Notably, the macro container_of triggers the alignment warning for container_of, so I have a set of alignment warnings, and a set of deprecation warnings. But it builds. The incremental patch would be something like:


diff --git a/configure.ac b/configure.ac
index ecab365..8b433ba 100644
--- a/configure.ac
+++ b/configure.ac
@@ -481,7 +481,8 @@ if test "$with_coroutine" = "auto"; then
   if test "$os_win32" = "yes"; then
     with_coroutine=winfiber
   elif test "$os_mac" = "yes"; then
-    with_coroutine=gthread
+    with_coroutine=ucontext
+    AC_DEFINE([_XOPEN_SOURCE], [1], [Define _XOPEN_SOURCE on macOS for ucontext])
   else
     with_coroutine=ucontext
   fi
diff --git a/src/continuation.h b/src/continuation.h
index 675a257..cbca06e 100644
--- a/src/continuation.h
+++ b/src/continuation.h
@@ -49,7 +49,7 @@ int cc_swap(struct continuation *from, struct continuation *to);
 
 #define offset_of(type, member) ((unsigned long)(&((type *)0)->member))
 #define container_of(obj, type, member) \
-        (type *)(((char *)obj) - offset_of(type, member))
+        (type *)(void *)(((char *)obj) - offset_of(type, member))
 
 #endif
 /*

Would that be better in your opinion?


Christophe

> 
> Regards,
> Daniel
> -- 
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