[libcxx] Add missing __cxa_deleted_virtual

[eduardo-elizondo]

Summary

At least on macOS, libc++ fails to advertise __cxa_deleted_virtual from the underlying libc++abi:

~ cat test.cc
struct S { virtual void f() = delete; };
int main() { new S; }

~ clang++ -v -std=c++11 test.cc
Apple LLVM version 8.1.0 (clang-802.0.42)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.12.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name test.cc -mrelocation-model pic -pic-level 2 -mthread-model posix -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu penryn -target-linker-version 278.4 -v -dwarf-column-info -debugger-tuning=lldb -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/8.1.0 -stdlib=libc++ -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /Users/stephan -ferror-limit 19 -fmessage-length 132 -stack-protector 1 -fblocks -fobjc-runtime=macosx-10.12.0 -fencode-extended-block-signature -fcxx-exceptions -fexceptions -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/q3/7lltvjlj4_l44qtq0fjz_slh0000gn/T/test-f1e908.o -x c++ test.cc
clang -cc1 version 8.1.0 (clang-802.0.42) default target x86_64-apple-darwin16.7.0
ignoring nonexistent directory "/usr/include/c++/v1"
ignoring nonexistent directory "/usr/local/include"
#include "..." search starts here:
#include <...> search starts here:
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/8.1.0/include
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
 /usr/include
 /System/Library/Frameworks (framework directory)
 /Library/Frameworks (framework directory)
End of search list.
 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -lto_library /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/libLTO.dylib -no_deduplicate -dynamic -arch x86_64 -macosx_version_min 10.12.0 -o a.out /var/folders/q3/7lltvjlj4_l44qtq0fjz_slh0000gn/T/test-f1e908.o -lc++ -lSystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/8.1.0/lib/darwin/libclang_rt.osx.a
Undefined symbols for architecture x86_64:
  "___cxa_deleted_virtual", referenced from:
      vtable for S in test-f1e908.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

I have no real idea what all these various files are used for, and which changes exactly are required and correct. Just adding cxa_deleted_virtual to all files in libcxx that already mentioned cxa_pure_virtual and doing a fresh build fixed the issue for me on macOS (after fruitless attempts with changing only a subset of the files and/or doing an incremental rebuild).

[mclow.lists]

In an ideal world, your example would fail to compile. However, we don't live in that world. (yet) :-(
This looks reasonable to me - but I didn't write these files - @EricWF - what do you think?

Also, from an organizational point of view, I would put these next to (and make them identical to) the entries for ___cxa_pure_virtual (which you have for some, but not all of the files)

[EricWF]

lib/abi/3.9/x86_64-apple-darwin16.abilist

2284 ↗

(On Diff #111653)

Files under lib/abi/<version> should not be changed. They're for already released versions of libc++, and this change doesn't affect those.

lib/abi/x86_64-unknown-linux-gnu.abilist

1873

Why are we changing the Linux lists when this change only affects OS X?

[sberg]

lib/abi/x86_64-unknown-linux-gnu.abilist

1873

As I wrote, "I have no real idea what all these various files are used for, and which changes exactly are required and correct. Just adding cxa_deleted_virtual to all files in libcxx that already mentioned cxa_pure_virtual [...]" The way libc++.so on Linux consists of

INPUT(libc++.so.1 -lc++abi)

it does not need the fix that macOS needs to make cxa_deleted_virtual available through -lc++, but it still "re-exports" cxa_deleted_virtual the same way it does for __cxa_pure_virtual (which is also mentioned in this file), so I naively assumed it should be listed here, too.

[eduardo-elizondo]

Any updates on this? I'm also hitting this bug.

[sberg]

Drop changes of files under lib/abi/<version>.

[eduardo-elizondo]

D37830 supersedes this change.

[sberg]

...but I'm still curious as to why lib/abi/x86_64-unknown-linux-gnu.abilist should want to mention __cxa_pure_virtual but not __cxa_deleted_virtual

[EricWF]

In D36870#871739, @sberg wrote:

...but I'm still curious as to why lib/abi/x86_64-unknown-linux-gnu.abilist should want to mention __cxa_pure_virtual but not __cxa_deleted_virtual

Because libc++ doesn't actually have any instances of deleted virtual functions within the library __cxa_deleted_vilrtual is never used, and hence never exported on Linux.
We do, however, have pure virtual functions, so __cxa_pure_virtual is exported transitively. On Linux we don't use the explicit export lists, so this change didn't change the Linux ABI.

Do you need somebody to commit this for you?

[sberg]

In D36870#871740, @EricWF wrote:

Because libc++ doesn't actually have any instances of deleted virtual functions within the library __cxa_deleted_vilrtual is never used, and hence never exported on Linux.
We do, however, have pure virtual functions, so __cxa_pure_virtual is exported transitively. On Linux we don't use the explicit export lists, so this change didn't change the Linux ABI.

Ah, I see. Thanks.

Do you need somebody to commit this for you?

No, as this has been abandoned in favour of D37830 anyway.

lib/abi/x86_64-apple-darwin16.abilist

 {'type': 'U', 'is_defined': False, 'name': '___cxa_begin_catch'}
 {'type': 'I', 'is_defined': True, 'name': '___cxa_begin_catch'}
 {'type': 'U', 'is_defined': False, 'name': '___cxa_call_unexpected'}
 {'type': 'I', 'is_defined': True, 'name': '___cxa_call_unexpected'}
 {'type': 'U', 'is_defined': False, 'name': '___cxa_current_exception_type'}
 {'type': 'I', 'is_defined': True, 'name': '___cxa_current_exception_type'}
 {'type': 'U', 'is_defined': False, 'name': '___cxa_current_primary_exception'}
 {'type': 'U', 'is_defined': False, 'name': '___cxa_decrement_exception_refcount'}
+{'type': 'U', 'is_defined': False, 'name': '___cxa_deleted_virtual'}
+{'type': 'I', 'is_defined': True, 'name': '___cxa_deleted_virtual'}
 {'type': 'U', 'is_defined': False, 'name': '___cxa_demangle'}
 {'type': 'I', 'is_defined': True, 'name': '___cxa_demangle'}
 {'type': 'U', 'is_defined': False, 'name': '___cxa_end_catch'}
 {'type': 'I', 'is_defined': True, 'name': '___cxa_end_catch'}
 {'type': 'U', 'is_defined': False, 'name': '___cxa_free_exception'}
 {'type': 'I', 'is_defined': True, 'name': '___cxa_free_exception'}
 {'type': 'U', 'is_defined': False, 'name': '___cxa_get_exception_ptr'}
 {'type': 'I', 'is_defined': True, 'name': '___cxa_get_exception_ptr'}

lib/abi/x86_64-unknown-linux-gnu.abilist

 {'is_defined': True, 'name': '_Znwm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZnwmRKSt9nothrow_t', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZnwmSt11align_val_t', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZnwmSt11align_val_tRKSt9nothrow_t', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_allocate_exception', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_begin_catch', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_current_primary_exception', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_decrement_exception_refcount', 'type': 'FUNC'}
+{'is_defined': False, 'name': '__cxa_deleted_virtual', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_end_catch', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_free_exception', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_guard_abort', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_guard_acquire', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_guard_release', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_increment_exception_refcount', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_pure_virtual', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_rethrow', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_rethrow_primary_exception', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_throw', 'type': 'FUNC'}
 {'is_defined': False, 'name': '__cxa_uncaught_exception', 'type': 'FUNC'}

lib/libc++abi.exp

 ___cxa_allocate_exception
 ___cxa_end_catch
 ___cxa_demangle
 ___cxa_current_exception_type
 ___cxa_call_unexpected
 ___cxa_free_exception
 ___cxa_get_exception_ptr
 ___cxa_get_globals
 ___cxa_get_globals_fast
 ___cxa_guard_abort
 ___cxa_guard_acquire
 ___cxa_guard_release
 ___cxa_rethrow
 ___cxa_pure_virtual
+___cxa_deleted_virtual
 ___cxa_begin_catch
 ___cxa_throw
 ___cxa_vec_cctor
 ___cxa_vec_cleanup
 ___cxa_vec_ctor
 ___cxa_vec_delete
 ___cxa_vec_delete2
 ___cxa_vec_delete3

lib/libc++abi2.exp

 ___cxa_allocate_exception
 ___cxa_end_catch
 ___cxa_demangle
 ___cxa_current_exception_type
 ___cxa_call_unexpected
 ___cxa_free_exception
 ___cxa_get_exception_ptr
 ___cxa_get_globals
 ___cxa_get_globals_fast
 ___cxa_guard_abort
 ___cxa_guard_acquire
 ___cxa_guard_release
 ___cxa_rethrow
 ___cxa_pure_virtual
+___cxa_deleted_virtual
 ___cxa_begin_catch
 ___cxa_throw
 ___cxa_vec_cctor
 ___cxa_vec_cleanup
 ___cxa_vec_ctor
 ___cxa_vec_delete
 ___cxa_vec_delete2
 ___cxa_vec_delete3

lib/libc++sjlj-abi.exp

 ___cxa_allocate_exception
 ___cxa_end_catch
 ___cxa_demangle
 ___cxa_current_exception_type
 ___cxa_call_unexpected
 ___cxa_free_exception
 ___cxa_get_exception_ptr
 ___cxa_get_globals
 ___cxa_get_globals_fast
 ___cxa_guard_abort
 ___cxa_guard_acquire
 ___cxa_guard_release
 ___cxa_rethrow
 ___cxa_pure_virtual
+___cxa_deleted_virtual
 ___cxa_begin_catch
 ___cxa_throw
 ___cxa_vec_cctor
 ___cxa_vec_cleanup
 ___cxa_vec_ctor
 ___cxa_vec_delete
 ___cxa_vec_delete2
 ___cxa_vec_delete3