Merge lp:~alan-griffiths/mir/fix-1617865 into lp:mir

[Alan Griffiths]

Fix the accidental move of mir::dispatch::ReadableFd symbols from MIR_COMMON_5.1 to MIR_COMMON_0.24 (LP:1617865)

[Mir CI Bot (mir-ci-bot)]

FAILED: Continuous integration, rev:3711
https://mir-jenkins.ubuntu.com/job/mir-ci/1756/
Executed test runs:
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-mir/2203/console
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/2266
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/2257
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/2257
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=yakkety/2257
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/2231/console
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2231/console
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/2231/console
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/2231/console
    FAILURE: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/2231/console

Click here to trigger a rebuild:
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review: Needs Fixing (continuous-integration)

[Brandon Schaefer (brandontschaefer)]

+1

review: Approve

[Alan Griffiths (alan-griffiths)]

Ooh! This might be a problem...

16:30:48 cd /<<BUILDDIR>>/mir-0.25.0+xenial2257bzr3711/obj-x86_64-linux-gnu && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /<<BUILDDIR>>/mir-0.25.0+xenial2257bzr3711 /<<BUILDDIR>>/mir-0.25.0+xenial2257bzr3711/tests/mir_test_doubles /<<BUILDDIR>>/mir-0.25.0+xenial2257bzr3711/obj-x86_64-linux-gnu /<<BUILDDIR>>/mir-0.25.0+xenial2257bzr3711/obj-x86_64-linux-gnu/tests/mir_test_doubles /<<BUILDDIR>>/mir-0.25.0+xenial2257bzr3711/obj-x86_64-linux-gnu/tests/mir_test_doubles/CMakeFiles/mir-test-doubles-platform-static.dir/DependInfo.cmake --color=
16:30:48 [ 48%] Built target mirclientrpc
16:30:48 make -f examples/CMakeFiles/mir_demo_server.dir/build.make examples/CMakeFiles/mir_demo_server.dir/depend
16:30:48 /tmp/cchcbiRQ.s: Assembler messages:
16:30:48 /tmp/cchcbiRQ.s:345: Error: multiple versions [`_ZN3mir8dispatch10ReadableFdD0Ev@@@MIR_COMMON_5.1'|`_ZN3mir8dispatch10ReadableFdD0Ev@MIR_COMMON_0.24'] for symbol `_ZN3mir8dispatch10ReadableFdD0Ev'
16:30:48 /tmp/cchcbiRQ.s:346: Error: multiple versions [`_ZTVN3mir8dispatch10ReadableFdE@@@MIR_COMMON_5.1'|`_ZTVN3mir8dispatch10ReadableFdE@MIR_COMMON_0.24'] for symbol `_ZTVN3mir8dispatch10ReadableFdE'
16:30:48 /tmp/cchcbiRQ.s:347: Error: multiple versions [`_ZN3mir8dispatch10ReadableFdC2ENS_2FdERKSt8functionIFvvEE@@@MIR_COMMON_5.1'|`_ZN3mir8dispatch10ReadableFdC2ENS_2FdERKSt8functionIFvvEE@MIR_COMMON_0.24'] for symbol `_ZN3mir8dispatch10ReadableFdC2ENS_2FdERKSt8functionIFvvEE'
16:30:48 /tmp/cchcbiRQ.s:773: Error: multiple versions [`_ZNK3mir8dispatch10ReadableFd8watch_fdEv@@@MIR_COMMON_5.1'|`_ZNK3mir8dispatch10ReadableFd8watch_fdEv@MIR_COMMON_0.24'] for symbol `_ZNK3mir8dispatch10ReadableFd8watch_fdEv'
16:30:48 /tmp/cchcbiRQ.s:806: Error: multiple versions [`_ZN3mir8dispatch10ReadableFd8dispatchEj@@@MIR_COMMON_5.1'|`_ZN3mir8dispatch10ReadableFd8dispatchEj@MIR_COMMON_0.24'] for symbol `_ZN3mir8dispatch10ReadableFd8dispatchEj'
16:30:48 /tmp/cchcbiRQ.s:854: Error: multiple versions [`_ZNK3mir8dispatch10ReadableFd15relevant_eventsEv@@@MIR_COMMON_5.1'|`_ZNK3mir8dispatch10ReadableFd15relevant_eventsEv@MIR_COMMON_0.24'] for symbol `_ZNK3mir8dispatch10ReadableFd15relevant_eventsEv'
16:30:48 src/common/CMakeFiles/mircommon.dir/build.make:113: recipe for target 'src/common/CMakeFiles/mircommon.dir/dispatch/readable_fd.cpp.o' failed
16:30:48 make[3]: *** [src/common/CMakeFiles/mircommon.dir/dispatch/readable_fd.cpp.o] Error 1
16:30:48 make[3]: Leaving directory '/<<BUILDDIR>>/mir-0.25.0+xenial2257bzr3711/obj-x86_64-linux-gnu'
16:30:48 CMakeFiles/Makefile2:2791: recipe for target 'src/common/CMakeFiles/mircommon.dir/all' failed
16:30:48 make[2]: *** [src/common/CMakeFiles/mircommon.dir/all] Error 2
16:30:48 make[2]: *** Waiting for unfinished jobs....

https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2231/console

[Alan Griffiths (alan-griffiths)]

> Ooh! This might be a problem...
>
It is. clang "does the right thing" but gcc doesn't understand this approach.

review: Needs Fixing

[Daniel van Vugt (vanvugt)]

I wish you luck.

Isn't @@@ meant to be just @@ ?

[Alan Griffiths (alan-griffiths)]

> I wish you luck.
>
> Isn't @@@ meant to be just @@ ?

I thought so too. But I found the symbol wasn't exported with that and needed to be @@@ - like the example in doc/dso_versioning_guide.md.

What I overlooked was that I was using clang - which behaves differently to gcc. I need to RTFM.

[Alan Griffiths (alan-griffiths)]

Hmm...

    Honestly, this is an assembler bug, but we've been working around
    it for years. Here you have to jump though silly hoops, and create
    an alternate base symbol via an alias. E.g.

    weak_alias (__mcount, __mcount1)
    versioned_symbol (libc, __mcount, _mcount, GLIBC_2_18)
    versioned_symbol (libc, __mcount1, mcount, GLIBC_2_18)

    There are other examples in the source base for similar if you go
    grepping...

https://sourceware.org/ml/libc-alpha/2013-07/msg00480.html

[Mir CI Bot (mir-ci-bot)]

PASSED: Continuous integration, rev:3712
https://mir-jenkins.ubuntu.com/job/mir-ci/1771/
Executed test runs:
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-mir/2219
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/2282
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/2273
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/2273
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=yakkety/2273
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/2247
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/2247/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2247
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2247/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/2247
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/2247/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/2247
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/2247/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/2247
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/2247/artifact/output/*zip*/output.zip

Click here to trigger a rebuild:
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review: Approve (continuous-integration)

[Alan Griffiths (alan-griffiths)]

This is weird. After the gcc assembler complaining about them in the last iteration it is now failing to emit the versioned symbols.

This seems to be specific to C++ symbols - I tried cut & paste of some incantations from Mir-0.13 and that works.

Maybe this approach only works with clang?

[Alan Griffiths (alan-griffiths)]

Showing it to CI, but the gcc version still doesn't publish the versioned aliases from libmircommon.

review: Disapprove

[Mir CI Bot (mir-ci-bot)]

PASSED: Continuous integration, rev:3715
https://mir-jenkins.ubuntu.com/job/mir-ci/1773/
Executed test runs:
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-mir/2221
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/2284
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/2275
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/2275
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=yakkety/2275
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/2250
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/2250/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2250
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2250/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/2250
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/2250/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/2250
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/2250/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/2250
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/2250/artifact/output/*zip*/output.zip

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review: Approve (continuous-integration)

[Daniel van Vugt (vanvugt)]

Maybe symbols.map is conflicting/overriding this...

Maybe also consider using two separate compilation units (cpp files) with just a different symbol version in each.

[lp:~alan-griffiths/mir/fix-1617865]

3716. By Alan Griffiths on 2016-09-21

Code cleanup

[Alan Griffiths (alan-griffiths)]

The problem appear to be that for C++ symbols the gcc assembler exports the unversioned symbols as well as the versioned ones whereas the clang assembler just exports the versioned aliases.

With gcc the linker then resolves to the unversioned symbols (and ignores the versioned ones).

Marking the unversioned symbol names .local doesn't help.

[Mir CI Bot (mir-ci-bot)]

PASSED: Continuous integration, rev:3716
https://mir-jenkins.ubuntu.com/job/mir-ci/1780/
Executed test runs:
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-mir/2230
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/2293
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=vivid+overlay/2284
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/2284
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=yakkety/2284
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/2258
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=yakkety/2258/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2258
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/2258/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/2258
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=yakkety/2258/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/2258
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=android,release=vivid+overlay/2258/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/2258
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/2258/artifact/output/*zip*/output.zip

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review: Approve (continuous-integration)

Unmerged revisions

3716. By Alan Griffiths on 2016-09-21

Code cleanup

3715. By Alan Griffiths on 2016-09-20

Incantation for the vtab

3714. By Alan Griffiths on 2016-09-20

Delete test code

3713. By Alan Griffiths on 2016-09-20

Get the versioned aliases into the .o. (Shame about the .so)

3712. By Alan Griffiths on 2016-09-20

Work around undocumented behaviour of gcc and clang toolchains

3711. By Alan Griffiths on 2016-09-19

Provide mir::dispatch::ReadableFd symbols in both MIR_COMMON_5.1 and MIR_COMMON_0.24

=== modified file 'src/common/dispatch/readable_fd.cpp'
--- src/common/dispatch/readable_fd.cpp	2015-08-29 11:33:37 +0000
+++ src/common/dispatch/readable_fd.cpp	2016-09-21 10:45:32 +0000
@@ -18,17 +18,47 @@
 
 #include "mir/dispatch/readable_fd.h"
 
+// Fix for lp:1617865
+//
+// "Accidental libmircommon.so.6 ABI break in Mir 0.24: mir::dispatch::ReadableFd*
+// moved version stanzas
+//
+// "So for example server-mesa-x11.so.9 can no longer load because it expects from
+// libmircommon.so.6:
+//      ZN3mir8dispatch10ReadableFdC1ENS_2FdERKSt8functionIFvvEE@MIR_COMMON_5.1
+// but actually in Mir 0.24.0 that got duplicated and changed to:
+//      ZN3mir8dispatch10ReadableFdC1ENS_2FdERKSt8functionIFvvEE@MIR_COMMON_0.24"
+//
+// Move the default symbol back to MIR_COMMON_5.1 and also provide MIR_COMMON_0.24
+
+// NB Neither the gcc nor clang toolchain behaves as I read the documentation, but,
+// in practice, these incantations work around the differences.     ~ alan_g
+#if   defined(__clang__)
+#define MIR_DOUBLE_ENTRY(symbol)\
+__asm__(".symver " #symbol "," #symbol "@MIR_COMMON_0.24");\
+__asm__(".symver " #symbol "," #symbol "@@@MIR_COMMON_5.1")
+#elif defined(__GNUC__)
+#define MIR_DOUBLE_ENTRY(symbol)\
+extern "C"  __attribute__ ((alias(#symbol))) void _X##symbol();\
+__asm__(".symver _X" #symbol "," #symbol "@MIR_COMMON_0.24");\
+__asm__(".symver   " #symbol "," #symbol "@@MIR_COMMON_5.1")
+#endif
+
+MIR_DOUBLE_ENTRY(_ZN3mir8dispatch10ReadableFdC1ENS_2FdERKSt8functionIFvvEE);
+MIR_DOUBLE_ENTRY(_ZN3mir8dispatch10ReadableFdC2ENS_2FdERKSt8functionIFvvEE);
 mir::dispatch::ReadableFd::ReadableFd(Fd fd, std::function<void()> const& on_readable) :
     fd{fd},
     readable{on_readable}
 {
 }
 
+MIR_DOUBLE_ENTRY(_ZNK3mir8dispatch10ReadableFd8watch_fdEv);
 mir::Fd mir::dispatch::ReadableFd::watch_fd() const
 {
     return fd;
 }
 
+MIR_DOUBLE_ENTRY(_ZN3mir8dispatch10ReadableFd8dispatchEj);
 bool mir::dispatch::ReadableFd::dispatch(FdEvents events)
 {
     if (events & FdEvent::error)
@@ -40,7 +70,20 @@
     return true;
 }
 
+MIR_DOUBLE_ENTRY(_ZNK3mir8dispatch10ReadableFd15relevant_eventsEv);
 mir::dispatch::FdEvents mir::dispatch::ReadableFd::relevant_events() const
 {
     return FdEvent::readable;
 }
+
+#if !defined(__clang__) && defined(__GNUC__)
+#undef MIR_DOUBLE_ENTRY
+#define MIR_DOUBLE_ENTRY(symbol)\
+__asm__(".weakref _X" #symbol "," #symbol);\
+__asm__(".symver _X" #symbol "," #symbol "@MIR_COMMON_0.24");\
+__asm__(".symver   " #symbol "," #symbol "@@MIR_COMMON_5.1")
+#endif
+
+MIR_DOUBLE_ENTRY(_ZTVN3mir8dispatch10ReadableFdE);  // vtable for mir::dispatch::ReadableFd
+MIR_DOUBLE_ENTRY(_ZTIN3mir8dispatch10ReadableFdE);  // typeinfo for mir::dispatch::ReadableFd
+MIR_DOUBLE_ENTRY(_ZTSN3mir8dispatch10ReadableFdE);  // typeinfo name for mir::dispatch::ReadableFd