Make the Google Go programming language available on GNU/Hurd in its GCC gccgo implementation, and enable Hurd-specific features.
There is a FOSS Factory bounty (p263) on this task.
Part I
First, make the language functional, have its test suite pass without errors.
Original GSoC Task Description
Obsolete
This is no longer valid as a Google Summer of Code project; existing work needs to be integrated first.
The goal of this project is to make the Google Go programming language available on GNU/Hurd in its GCC gccgo implementation.
Presumably less work will be needed on the language's frontend itself, but rather on the supporting libraries.
Apart from a solid knowledge of the ?POSIX API, working knowledge of the Google Go programming language is a must. Some Hurd knowledge will have to be acquired while working on the project.
Designing and implementing language bindings is a follow-up project.
Possible mentors: Ian Lance Taylor: gccgo bits, Thomas Schwinge (tschwinge): Hurd bits.
Exercise: Fix one of the problems preventing gccgo from working on the Hurd.
Open Issue page. Entry in the GCC wiki.
tschwinge/t/hurd/go
There is now a tschwinge/t/hurd/go branch in GCC's Git repository, where the
Hurd port for Go is being polished.
getcontext/makecontext/setcontext/swapcontext usage analysis
In context of tls-threadvar. Looking at GCC trunk commit f6568ea476aa52a6e23c6db43b3e240cde55783a (2013-04-26).
The check in libgo/configure.ac whether setcontext clobbers TLS variables
is invalid on GNU Hurd.
The *context functions are used in libgo/runtime/go-signal.c and
libgo/runtime/proc.c.
__splitstack_getcontext, __splitstack_setcontext,
__splitstack_makecontext, __splitstack_resetcontext,
__splitstack_block_signals_context are to be provided by libgcc. However, in
said libgo runtime files, they're used only #ifdef USING_SPLIT_STACK.
I would assume that before we can enable split stacks, first
tls-threadvar needs to be fixed.
In libgo/runtime/proc.c:runtime_gogo, setcontext is used to switch
context to a different goroutine. TODO.
In libgo/runtime/proc.c:runtime_mcall, which save[s] context and call[s]
fn passing g as a parameter, getcontext and setcontext are used; this is
only called from libgo/runtime/proc.c:runtime_gosched. TODO.
In libgo/runtime/proc.c:runtime_tracebackothers, getcontext is used to
switch context to the goroutine. TODO.
In libgo/runtime/proc.c:runtime_mstart, which is called to start an M,
getcontext is used. TODO.
In libgo/runtime/proc.c:runtime_entersyscall, which is called when the
goroutine g is about to enter a system call, getcontext is used to save the
registers in the g structure so that any pointers held in registers will be
seen by the garbage collector. Should be fine.
In libgo/runtime/proc.c:__go_go, getcontext and makecontext are used.
TODO.
In libgo/runtime/thread.c:runtime_minit, which is [c]alled to initialize a
new m (including the bootstrap m), ss.ss_sp is set to a new stack retrieved
via libgo/runtime/proc.c:runtime_malg, which allocate[s] a new g, with a
stack [...], and then sigaltstack is called. TODO.
libgo/runtime/go-signal.c: /* We are now running on the stack registered via sigaltstack.
libgo/runtime/go-signal.c: and sigaltstack when the program starts.) */
libgo/runtime/proc.c: vnewg->context.uc_stack.ss_sp = vsp;
libgo/runtime/proc.c: vnewg->context.uc_stack.ss_sp += vspsize;
libgo/runtime/proc.c: vnewg->context.uc_stack.ss_size = vspsize;
Also, in libgo/runtime/proc.c:runtime_newm, pthread_attr_setstacksize is
used, which we also can't support yet, for the same reason.
2013-07-15, Fotis
gccgo manages to get compiled and pass a fair amount of its tests, however its library is failing all but one of its tests.
Following are the results of the passing suite between the libgo tests run on linux (x86) and the Hurd:
the Hurd:
Test Run By root on Fri Jul 12 17:56:44 UTC 2013
Native configuration is i686-unknown-gnu0.3
=== libgo tests ===
Schedule of variations:
unix
...
=== libgo Summary ===
# of expected passes 1
# of unexpected failures 130
/root/gcc_new/gccbuild/./gcc/gccgo version 4.9.0 20130606 (experimental) (GCC)
Linux results:
Test Run By fotis on Τρι 02 Ιούλ 2013 09:20:20 μμ EEST
Native configuration is i686-pc-linux-gnu
=== libgo tests ===
Schedule of variations:
unix
...
=== libgo Summary ===
# of expected passes 131
/home/fotis/Software/gcc_build/./gcc/gccgo version 4.9.0 20130702 (experimental) (GCC)
SIGCHLD busy-loops
I have no recollection anymore what this is about...
(gdb) thread apply all bt
Thread 3 (Thread 19802.3):
#0 0x01daab5c in swtch_pri () at /usr/src/eglibc-2.17/build-tree/hurd-i386-libc/mach/swtch_pri.S:2
#1 0x01dac544 in __spin_lock_solid (lock=0x1fb700c) at spin-solid.c:26
#2 0x01dc1e07 in __spin_lock (__lock=<optimized out>) at ../mach/lock-intern.h:54
#3 _hurd_sigstate_lock (ss=ss@entry=0x2b008) at hurdsig.c:172
#4 0x01deaefb in __sigprocmask (how=how@entry=2, set=set@entry=0x209ffc9c, oset=oset@entry=0x0) at ../sysdeps/mach/hurd/sigprocmask.c:43
#5 0x01deeaff in abort () at abort.c:67
#6 0x01dec7c3 in __sigreturn (scp=0x209ffd00) at ../sysdeps/mach/hurd/i386/sigreturn.c:74
#7 0x01dc6ac6 in trampoline () from /lib/i386-gnu/libc.so.0.3
#8 0x209ffd00 in ?? ()
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
Thread 2 (Thread 19802.2):
#0 0x01daaafc in mach_msg_trap () at /usr/src/eglibc-2.17/build-tree/hurd-i386-libc/mach/mach_msg_trap.S:2
#1 0x01dab3be in __mach_msg (msg=msg@entry=0x23fdef0, option=option@entry=3, send_size=32, rcv_size=rcv_size@entry=4096, rcv_name=rcv_name@entry=100, timeout=timeout@entry=0, notify=notify@entry=0) at msg.c:110
#2 0x01dabaeb in __mach_msg_server_timeout (demux=demux@entry=0x1dbc9f0 <msgport_server>, max_size=max_size@entry=4096, rcv_name=rcv_name@entry=100, option=option@entry=0, timeout=timeout@entry=0) at msgserver.c:150
#3 0x01dabbbb in __mach_msg_server (demux=demux@entry=0x1dbc9f0 <msgport_server>, max_size=4096, rcv_name=100) at msgserver.c:195
#4 0x01dbcaed in _hurd_msgport_receive () at msgportdemux.c:67
#5 0x01f54ab4 in entry_point (start_routine=0x1dbca80 <_hurd_msgport_receive>, arg=0x0) at ./pthread/pt-create.c:57
#6 0x00000000 in ?? ()
Thread 1 (Thread 19802.1):
#0 0x01daab5c in swtch_pri () at /usr/src/eglibc-2.17/build-tree/hurd-i386-libc/mach/swtch_pri.S:2
#1 0x01dac544 in __spin_lock_solid (lock=0x1fb700c) at spin-solid.c:26
#2 0x01dc1e07 in __spin_lock (__lock=<optimized out>) at ../mach/lock-intern.h:54
#3 _hurd_sigstate_lock (ss=ss@entry=0x1fb7808) at hurdsig.c:172
#4 0x01deaefb in __sigprocmask (how=1, set=0x0, oset=0x2004dc78) at ../sysdeps/mach/hurd/sigprocmask.c:43
#5 0x01dfe027 in getcontext () at ../sysdeps/mach/hurd/i386/getcontext.S:66
#6 0x012d4208 in runtime_mcall (pfn=0x12d4eb0 <schedule>) at ../../../go/libgo/runtime/proc.c:420
#7 0x012d48aa in runtime_gosched () at ../../../go/libgo/runtime/proc.c:1371
#8 0x012d4acf in syscall.Exitsyscall () at ../../../go/libgo/runtime/proc.c:1494
#9 0x012d1cc1 in runtime_MHeap_Scavenger (dummy=0x0) at ../../../go/libgo/runtime/mheap.c:453
#10 0x012d4946 in kickoff () at ../../../go/libgo/runtime/proc.c:370
#11 0x01dfe0ed in makecontext () at ../sysdeps/mach/hurd/i386/makecontext.S:95
#12 0x00000000 in ?? ()
(Perhaps in the mean time had received a SIGALARM or whatever DejaGnu sends
after timeout, if at all?)
-# of expected passes 1714
-# of unexpected failures 575
+# of expected passes 5067
+# of unexpected failures 12
# of expected failures 1
-# of untested testcases 13
+# of untested testcases 7
TODO
+go_net_cgo_file = go/net/cgo_linux.go
+go_net_sock_file = go/net/sock_gnu.go
copied from libgo/go/net/sock_bsd.go
+go_net_sockopt_file = go/net/sockopt_bsd.go
+go_net_sockoptip_file = go/net/sockoptip_bsd.go go/net/sockoptip_posix.go
+go_os_sys_file = go/os/sys_uname.go
+go_os_stat_file = go/os/stat_atim.go
+archive_tar_atim_file = go/archive/tar/stat_atim.go
+syscall_exec_file = go/syscall/exec_unix.go
+syscall_exec_os_file = go/syscall/exec_gnu.go
copied from libgo/go/syscall/exec_bsd.go
+syscall_libcall_file = go/syscall/libcall_gnu.go
copied from libgo/go/syscall/libcall_posix.go
updated
? go_net_poll_file
? go_net_fd_os_file
libgo/runtime/proc.c | 10 +-
libgo/runtime/thread.c | 7 +
(some?) code moved elsewhere (runtime_m()->gsignal = runtime_malg(...))
New libgo/go/reflect/makefunc_386.S and libgo/go/reflect/makefunc_amd64.S
contain Linux thingy. Review x86 one anyway. Also:
libgo/go/reflect/makefuncgo_386.go.
--- ./libgo/go/syscall/libcall_posix.go
+++ ./libgo/go/syscall/libcall_posix.go
-const nfdbits = int(unsafe.Sizeof(fds_bits_type) * 8)
+const nfdbits = int(unsafe.Sizeof(fds_bits_type(0)) * 8)
Have then not anymore reviewed Go changes in GCC -- have to restart this from scratch.
Part II
Next, Hurd-specific features can be added. Add an interface to the language/environment for being able to do RPC calls, in order to program translators natively in the Google Go programming language.
Original GSoC Task Description
The main idea of the Hurd design is giving users the ability to easily modify/extend the system's functionality (extensible system). This is done by creating filesystem translators and other kinds of Hurd servers.
However, in practice this is not as easy as it should, because creating translators and other servers is quite involved -- the interfaces for doing that are not exactly simple, and available only for C programs. Being able to easily create simple translators in RAD languages is highly desirable, to really be able to reap the advantages of the Hurd architecture.
Originally Lisp was meant to be the second system language besides C in the GNU system; but that doesn't mean we are bound to Lisp. Bindings for any popular high-level language, that helps quickly creating simple programs, are highly welcome.
Several approaches are possible when creating such bindings. One way is simply to provide wrappers to all the available C libraries (libtrivfs, libnetfs etc.). While this is easy (it requires relatively little consideration), it may not be the optimal solution. It is preferable to hook in at a lower level, thus being able to create interfaces that are specially adapted to make good use of the features available in the respective language.
These more specialized bindings could hook in at some of the lower level library interfaces (libports, glibc, etc.); use the MIG-provided RPC stubs directly; or even create native stubs directly from the interface definitions. The lisp bindings created by Flavio Cruz as his 2008 GSoC project mostly use the latter approach, and can serve as a good example. In his 2011 GSoC project, Jérémie Koenig designed and began implementing an object-oriented interface; see his Java status page for details.
The task is to create easy to use Hurd bindings for a language of the student's choice, and some example servers to prove that it works well in practice. This project will require gaining a very good understanding of the various Hurd interfaces. Skills in designing nice programming interfaces are a must.
Anatoly A. Kazantsev has started working on Python bindings last year -- if Python is your language of choice, you probably should take his work and complete it.
There was also some previous work on Perl bindings, which might serve as a reference if you want to work on Perl.
Possible mentors: Anatoly A. Kazantsev (anatoly) for Python
Discussion
Java
IRC, freenode, #hurd, 2013-12-19
<antrik_> teythoon_: I don't think wrapping libtrivfs etc. for guile
bindings is really desirable... for the lisp bindings, we agreed that
it's better to hook in at a lower level, and build more lispish
abstractions
<antrik> trivfs is a C framework; it probably doesn't map very well to
other languages -- especially non-imperative ones...
<antrik> (it is arguable whether trivfs is really a good abstraction even
for C... but that's another discussion :-) )
<antrik> ArneBab: same for Python bindings. when I suggested ignoring
libtrivfs etc., working around the pthread problem was just a side effect
-- the real goal has always been nicer abstraction
<anatoly> antrik: agree with you
<anatoly> antrik: about nicer abstractions
<teythoon_> antrik: I agree too, but wrapping libtrivfs is much easier
<teythoon_> otherwise, one needs to reimplement lots of stuff to get some
basic functionality
<teythoon_> like a mig that emits your language
<braunr> i agree with antrik too
<braunr> yes, the best would be mig handling multiple languages
<antrik> teythoon_: not exactly. for dynamic languages, code generation is
silly. just handle the marshalling on the fly. that's what the Lisp
bindings are doing (AFAIK)
<teythoon> antrik: ok, but you'd still need to parse the rpc definitions,
no?
<antrik> teythoon: yeah, you still need to parse the .defs -- unless we add
reflection to RPC interfaces...
<antrik> err, I mean introspection