RE: thread model for mxe-octave build

[JohnD]

> -----Original Message-----
> From: John W. Eaton [mailto:address@hidden
> Sent: Friday, February 23, 2018 9:08 AM
> To: JohnD; 'Octave Maintainers List'
> Subject: Re: thread model for mxe-octave build
> 
> On 02/22/2018 12:02 PM, JohnD wrote:
> >
> >
> >> -----Original Message-----
> >> From: John W. Eaton [mailto:address@hidden
> >> Sent: Thursday, February 22, 2018 11:44 AM
> >> To: John Donoghue; Octave Maintainers List
> >> Cc: address@hidden
> >> Subject: thread model for mxe-octave build
> >>
> >> I had someone ask why C++11 threads (mutext, condition_variable_any)
> >> wasn't working with .oct files built with Octave 4.2.1.  After a
> >> little searching, I found that we are configuring GCC with
> >> --enable-threads=win32 instead of --enable-threads=posix.  Apparently
> >> the latter is required to enable C++11 thread features.  Is there any
> >> reason to not use --enable-threads=posix by default in our builds?  I
> >> tried building native-gcc with this option and it allowed my test
> >> program to compile but I don't know whether there might be other
> >> problems.  From what I hve read, it seems that even if GCC is built
> >> with this option you can still use Windows threading features
> >> directly.  I've seen some mention of performance issues "in some 
> >> situations"
> but no explanation of what that might be.
> >>
> >> jwe
> >
> > No reason I know of except that mxe was/is using win32
> 
> I tried changing the following change:
> 
> diff --git a/src/build-gcc.mk b/src/build-gcc.mk
> --- a/src/build-gcc.mk
> +++ b/src/build-gcc.mk
> @@ -31,7 +31,7 @@ ifeq ($(MXE_SYSTEM),mingw)
>       --disable-nls \
>       --without-x \
>       --disable-win32-registry \
> -    --enable-threads=win32
> +    --enable-threads=posix
>     ifneq ($(TARGET),x86_64-w64-mingw32)
>       $(PKG)_SYSDEP_CONFIGURE_OPTIONS += \
>       --libdir='$(BUILD_TOOLS_PREFIX)/lib' \ diff --git a/src/native-gcc.mk
> b/src/native-gcc.mk
> --- a/src/native-gcc.mk
> +++ b/src/native-gcc.mk
> @@ -25,7 +25,7 @@ ifeq ($(MXE_SYSTEM),mingw)
>       --without-x \
>       --disable-win32-registry \
>       --with-native-system-header-dir='$(HOST_PREFIX)/include' \
> -    --enable-threads=win32
> +    --enable-threads=posix
>     ifneq ($(ENABLE_WINDOWS_64),yes)
>       $(PKG)_SYSDEP_CONFIGURE_OPTIONS += \
>         $(ENABLE_SHARED_OR_STATIC) \
> 
> The build-gcc target fails because pthread.h is not available:
> 
> In file included from
> /home/jwe/build/mxe-octave-w64-32-posix/tmp-build-gcc/gcc-
> 7.2.0/libgcc/gthr.h:148:0,
>                   from
> /home/jwe/build/mxe-octave-w64-32-posix/tmp-build-gcc/gcc-
> 7.2.0/libgcc/libgcov-interface.c:27:
> ./gthr-default.h:35:10: fatal error: pthread.h: No such file or directory
>   #include <pthread.h>
>            ^~~~~~~~~~~
> compilation terminated.
> Makefile:915: recipe for target '_gcov_dump.o' failed
> make[6]: *** [_gcov_dump.o] Error 1
> 
> Maybe this is just a dependency ordering issue, but I'm not sure how to fix 
> it.
> 
> Using --enable-threads=win32 for build-gcc and --enable-threads=posix for
> native-gcc allows the build to succeed, but I'm not sure that is a proper
> configuration.  Even if it is, we will also need to use posix threads for 
> build-gcc
> if we want to start using C++11 threading features in Octave itself.  Any 
> ideas
> about how to build a GCC cross compiler for Windows that has the posix thread
> model enabled?
> 
> jwe

Not sure what part of the gcc install that is, but the mxe version of gcc.mk 
compiles posix threads as part of gcc.mk, before building the 'rest of gcc'

And then all their pthreads.mk does is install a package config file for it