llvm-project/libcxx/docs/DesignDocs/VisibilityMacros.rst

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========================
Symbol Visibility Macros
========================
.. contents::
:local:
Overview
========
Libc++ uses various "visibility" macros in order to provide a stable ABI in
both the library and the headers. These macros work by changing the
visibility and inlining characteristics of the symbols they are applied to.
Visibility Macros
=================
**_LIBCPP_HIDDEN**
Mark a symbol as hidden so it will not be exported from shared libraries.
**_LIBCPP_FUNC_VIS**
Mark a symbol as being exported by the libc++ library. This attribute must
be applied to the declaration of all functions exported by the libc++ dylib.
**_LIBCPP_EXTERN_VIS**
Mark a symbol as being exported by the libc++ library. This attribute may
only be applied to objects defined in the libc++ library. On Windows this
macro applies `dllimport`/`dllexport` to the symbol. On all other platforms
this macro has no effect.
**_LIBCPP_OVERRIDABLE_FUNC_VIS**
Mark a symbol as being exported by the libc++ library, but allow it to be
overridden locally. On non-Windows, this is equivalent to `_LIBCPP_FUNC_VIS`.
This macro is applied to all `operator new` and `operator delete` overloads.
**Windows Behavior**: Any symbol marked `dllimport` cannot be overridden
locally, since `dllimport` indicates the symbol should be bound to a separate
DLL. All `operator new` and `operator delete` overloads are required to be
locally overridable, and therefore must not be marked `dllimport`. On Windows,
this macro therefore expands to `__declspec(dllexport)` when building the
library and has an empty definition otherwise.
**_LIBCPP_INLINE_VISIBILITY**
Mark a function as hidden and force inlining whenever possible.
**_LIBCPP_ALWAYS_INLINE**
A synonym for `_LIBCPP_INLINE_VISIBILITY`
**_LIBCPP_TYPE_VIS**
Mark a type's typeinfo, vtable and members as having default visibility.
This attribute cannot be used on class templates.
**_LIBCPP_TEMPLATE_VIS**
Mark a type's typeinfo and vtable as having default visibility.
This macro has no effect on the visibility of the type's member functions.
**GCC Behavior**: GCC does not support Clang's `type_visibility(...)`
attribute. With GCC the `visibility(...)` attribute is used and member
functions are affected.
**Windows Behavior**: DLLs do not support dllimport/export on class templates.
The macro has an empty definition on this platform.
**_LIBCPP_ENUM_VIS**
Mark the typeinfo of an enum as having default visibility. This attribute
should be applied to all enum declarations.
**Windows Behavior**: DLLs do not support importing or exporting enumeration
typeinfo. The macro has an empty definition on this platform.
**GCC Behavior**: GCC un-hides the typeinfo for enumerations by default, even
if `-fvisibility=hidden` is specified. Additionally applying a visibility
attribute to an enum class results in a warning. The macro has an empty
definition with GCC.
**_LIBCPP_EXTERN_TEMPLATE_TYPE_VIS**
Mark the member functions, typeinfo, and vtable of the type named in
a `_LIBCPP_EXTERN_TEMPLATE` declaration as being exported by the libc++ library.
This attribute must be specified on all extern class template declarations.
This macro is used to override the `_LIBCPP_TEMPLATE_VIS` attribute
specified on the primary template and to export the member functions produced
by the explicit instantiation in the dylib.
**GCC Behavior**: GCC ignores visibility attributes applied the type in
extern template declarations and applying an attribute results in a warning.
However since `_LIBCPP_TEMPLATE_VIS` is the same as
`__attribute__((visibility("default"))` the visibility is already correct.
The macro has an empty definition with GCC.
**Windows Behavior**: `extern template` and `dllexport` are fundamentally
incompatible *on a class template* on Windows; the former suppresses
instantiation, while the latter forces it. Specifying both on the same
declaration makes the class template be instantiated, which is not desirable
inside headers. This macro therefore expands to `dllimport` outside of libc++
but nothing inside of it (rather than expanding to `dllexport`); instead, the
explicit instantiations themselves are marked as exported. Note that this
applies *only* to extern *class* templates. Extern *function* templates obey
regular import/export semantics, and applying `dllexport` directly to the
extern template declaration (i.e. using `_LIBCPP_FUNC_VIS`) is the correct
thing to do for them.
**_LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS**
Mark the member functions, typeinfo, and vtable of an explicit instantiation
of a class template as being exported by the libc++ library. This attribute
must be specified on all class template explicit instantiations.
It is only necessary to mark the explicit instantiation itself (as opposed to
the extern template declaration) as exported on Windows, as discussed above.
On all other platforms, this macro has an empty definition.
[libc++] Make _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS export members When building libc++ with hidden visibility, we want explicit template instantiations to export members. This is consistent with existing Windows behavior, and is necessary for clients to be able to link against a hidden visibility built libc++ without running into lots of missing symbols. An unfortunate side effect, however, is that any template methods of a class with an explicit instantiation will get default visibility when instantiated, unless the methods are explicitly marked inline or hidden visibility. This is not desirable for clients of libc++ headers who wish to control their visibility, and led to PR30642. Annotate all problematic methods with an explicit visibility specifier to avoid this. The problematic methods were found by running https://github.com/smeenai/bad-visibility-finder against the libc++ headers after making the _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS change. The methods were marked with the new _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS macro, which was created for this purpose. It should be noted that _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS was originally intended to expand to default visibility, and was changed to expanding to default type visibility to fix PR30642. The visibility macro documentation was not updated accordingly, however, so this change makes the macro consistent with its documentation again, while explicitly fixing the methods which resulted in that PR. Differential Revision: https://reviews.llvm.org/D29157 llvm-svn: 296731
2017-03-02 11:02:50 +08:00
**_LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS**
Mark a symbol as hidden so it will not be exported from shared libraries. This
is intended specifically for method templates of either classes marked with
`_LIBCPP_TYPE_VIS` or classes with an extern template instantiation
declaration marked with `_LIBCPP_EXTERN_TEMPLATE_TYPE_VIS`.
When building libc++ with hidden visibility, we want explicit template
instantiations to export members, which is consistent with existing Windows
behavior. We also want classes annotated with `_LIBCPP_TYPE_VIS` to export
their members, which is again consistent with existing Windows behavior.
Both these changes are necessary for clients to be able to link against a
libc++ DSO built with hidden visibility without encountering missing symbols.
An unfortunate side effect, however, is that method templates of classes
either marked `_LIBCPP_TYPE_VIS` or with extern template instantiation
declarations marked with `_LIBCPP_EXTERN_TEMPLATE_TYPE_VIS` also get default
visibility when instantiated. These methods are often implicitly instantiated
inside other libraries which use the libc++ headers, and will therefore end up
being exported from those libraries, since those implicit instantiations will
receive default visibility. This is not acceptable for libraries that wish to
control their visibility, and led to PR30642.
Consequently, all such problematic method templates are explicitly marked
either hidden (via this macro) or inline, so that they don't leak into client
libraries. The problematic methods were found by running
`bad-visibility-finder <https://github.com/smeenai/bad-visibility-finder>`_
against the libc++ headers after making `_LIBCPP_TYPE_VIS` and
`_LIBCPP_EXTERN_TEMPLATE_TYPE_VIS` expand to default visibility.
[libc++] Add _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY to support GCC ABI compatibility Summary: GCC and Clang handle visibility attributes on the out-of-line definition of externally instantiated templates differently. For example in the reproducer below Clang will emit both 'foo' and 'bar' with default visibility while GCC only emits a non-hidden 'foo'. ``` // RUN: g++ -std=c++11 -shared -O3 test.cpp && sym_extract.py a.out // RUN: clang++ -std=c++11 -shared -O3 test.cpp && sym_extract.py a.out #define INLINE_VISIBILITY __attribute__((visibility("hidden"), always_inline)) template <class T> struct Foo { void foo(); void bar(); }; template <class T> void Foo<T>::foo() {} template <class T> inline INLINE_VISIBILITY void Foo<T>::bar() {} template struct Foo<int>; ``` This difference creates ABI incompatibilities between Clang and GCC built dylibs. Specifically GCC built dylibs lack definitions for various member functions of `basic_string`, `basic_istream`, `basic_ostream`, `basic_iostream`, and `basic_streambuf` (All of these types are externally instantiated). Surprisingly these missing symbols don't cause many problems because the functions are marked `always_inline` therefore the dylib definition is rarely needed. However when an out-of-line definition is required then GCC built dylibs will fail to link. For example [GCC built dylibs cannot build Clang](http://stackoverflow.com/questions/39454262/clang-build-errors). This patch works around this issue by adding `_LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY` which is used to mark externally instantiated member functions as always inline. When building the library `_LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY` sets the symbol's visibility to "default" instead of "hidden", otherwise it acts exactly the same as `_LIBCPP_INLINE_VISIBILITY`. After applying this patch GCC dylibs now contain: * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE7sungetcEv` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5gbumpEi` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE7sungetcEv` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE9sputbackcEc` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE3getERNS_15basic_streambufIwS2_EE` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEElsEPFRNS_9basic_iosIwS2_EES6_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE4setpEPcS4_` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEEC1EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE6snextcEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE4swapERS3_` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE4swapERS3_` * `_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEPKcm` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEErsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE9pubsetbufEPcl` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE10pubseekoffExNS_8ios_base7seekdirEj` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEErsEPFRNS_9basic_iosIwS2_EES6_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5pbumpEi` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5seekpENS_4fposI11__mbstate_tEE` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE7getlineEPcl` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sgetcEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE3getERNS_15basic_streambufIcS2_EE` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE8in_availEv` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEErsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE6sbumpcEv` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPFRNS_9basic_iosIcS2_EES6_E` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE3getERc` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE6snextcEv` * `_ZNSt3__112basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEE6__initEmw` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE7getlineEPwl` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5tellpEv` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE3getERw` * `_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEmc` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE7pubsyncEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE3getEPcl` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEEC2EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEErsEPFRNS_9basic_iosIcS2_EES6_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE7pubsyncEv` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sputcEc` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE5seekpExNS_8ios_base7seekdirE` * `_ZNKSt3__115basic_streambufIcNS_11char_traitsIcEEE6getlocEv` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5gbumpEi` * `_ZNSt3__114basic_iostreamIcNS_11char_traitsIcEEE4swapERS3_` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE5seekpENS_4fposI11__mbstate_tEE` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE5tellpEv` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEElsEPFRS3_S4_E` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE3getEPwl` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEEC2EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPFRS3_S4_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE4setgEPcS4_S4_` * `_ZNSt3__112basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEE6__initEPKwmm` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE4setgEPwS4_S4_` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEEC1EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE8pubimbueERKNS_6localeE` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE4swapERS3_` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEEC2EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE10pubseekposENS_4fposI11__mbstate_tEEj` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5pbumpEi` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sgetcEv` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE4swapERS3_` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE10pubseekposENS_4fposI11__mbstate_tEEj` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sputnEPKcl` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5seekpExNS_8ios_base7seekdirE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sgetnEPwl` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEElsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE4setpEPwS4_` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sgetnEPcl` * `_ZNKSt3__115basic_streambufIwNS_11char_traitsIwEEE6getlocEv` * `_ZNSt3__114basic_iostreamIcNS_11char_traitsIcEEEC2EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE8pubimbueERKNS_6localeE` * `_ZNSt3__114basic_iostreamIcNS_11char_traitsIcEEEC1EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE8in_availEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEEC1EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEPKcmm` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE6sbumpcEv` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE10pubseekoffExNS_8ios_base7seekdirEj` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEEC2EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEErsEPFRS3_S4_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE9sputbackcEw` * `_ZNSt3__112basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEE6__initEPKwm` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sputnEPKwl` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEErsEPFRS3_S4_E` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEEC1EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE9pubsetbufEPwl` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sputcEw` This patch has no effect on Clang based builds. Reviewers: mclow.lists, eugenis, danalbert, jroelofs, EricWF Subscribers: beanz, cfe-commits, mgorny Differential Revision: https://reviews.llvm.org/D24600 llvm-svn: 281681
2016-09-16 08:00:48 +08:00
**_LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY**
Mark a member function of a class template as visible and always inline. This
macro should only be applied to member functions of class templates that are
externally instantiated. It is important that these symbols are not marked
as hidden as that will prevent the dylib definition from being found.
[libc++] Add _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY to support GCC ABI compatibility Summary: GCC and Clang handle visibility attributes on the out-of-line definition of externally instantiated templates differently. For example in the reproducer below Clang will emit both 'foo' and 'bar' with default visibility while GCC only emits a non-hidden 'foo'. ``` // RUN: g++ -std=c++11 -shared -O3 test.cpp && sym_extract.py a.out // RUN: clang++ -std=c++11 -shared -O3 test.cpp && sym_extract.py a.out #define INLINE_VISIBILITY __attribute__((visibility("hidden"), always_inline)) template <class T> struct Foo { void foo(); void bar(); }; template <class T> void Foo<T>::foo() {} template <class T> inline INLINE_VISIBILITY void Foo<T>::bar() {} template struct Foo<int>; ``` This difference creates ABI incompatibilities between Clang and GCC built dylibs. Specifically GCC built dylibs lack definitions for various member functions of `basic_string`, `basic_istream`, `basic_ostream`, `basic_iostream`, and `basic_streambuf` (All of these types are externally instantiated). Surprisingly these missing symbols don't cause many problems because the functions are marked `always_inline` therefore the dylib definition is rarely needed. However when an out-of-line definition is required then GCC built dylibs will fail to link. For example [GCC built dylibs cannot build Clang](http://stackoverflow.com/questions/39454262/clang-build-errors). This patch works around this issue by adding `_LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY` which is used to mark externally instantiated member functions as always inline. When building the library `_LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY` sets the symbol's visibility to "default" instead of "hidden", otherwise it acts exactly the same as `_LIBCPP_INLINE_VISIBILITY`. After applying this patch GCC dylibs now contain: * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE7sungetcEv` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5gbumpEi` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE7sungetcEv` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE9sputbackcEc` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE3getERNS_15basic_streambufIwS2_EE` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEElsEPFRNS_9basic_iosIwS2_EES6_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE4setpEPcS4_` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEEC1EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE6snextcEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE4swapERS3_` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE4swapERS3_` * `_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEPKcm` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEErsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE9pubsetbufEPcl` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE10pubseekoffExNS_8ios_base7seekdirEj` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEErsEPFRNS_9basic_iosIwS2_EES6_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5pbumpEi` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5seekpENS_4fposI11__mbstate_tEE` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE7getlineEPcl` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sgetcEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE3getERNS_15basic_streambufIcS2_EE` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE8in_availEv` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEErsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE6sbumpcEv` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPFRNS_9basic_iosIcS2_EES6_E` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE3getERc` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE6snextcEv` * `_ZNSt3__112basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEE6__initEmw` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE7getlineEPwl` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5tellpEv` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE3getERw` * `_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEmc` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE7pubsyncEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE3getEPcl` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEEC2EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEErsEPFRNS_9basic_iosIcS2_EES6_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE7pubsyncEv` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sputcEc` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE5seekpExNS_8ios_base7seekdirE` * `_ZNKSt3__115basic_streambufIcNS_11char_traitsIcEEE6getlocEv` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5gbumpEi` * `_ZNSt3__114basic_iostreamIcNS_11char_traitsIcEEE4swapERS3_` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE5seekpENS_4fposI11__mbstate_tEE` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE5tellpEv` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEElsEPFRS3_S4_E` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE3getEPwl` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEEC2EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPFRS3_S4_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE4setgEPcS4_S4_` * `_ZNSt3__112basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEE6__initEPKwmm` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE4setgEPwS4_S4_` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEEC1EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE8pubimbueERKNS_6localeE` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE4swapERS3_` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEEC2EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE10pubseekposENS_4fposI11__mbstate_tEEj` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5pbumpEi` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sgetcEv` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE4swapERS3_` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE10pubseekposENS_4fposI11__mbstate_tEEj` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sputnEPKcl` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5seekpExNS_8ios_base7seekdirE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sgetnEPwl` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEElsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE4setpEPwS4_` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sgetnEPcl` * `_ZNKSt3__115basic_streambufIwNS_11char_traitsIwEEE6getlocEv` * `_ZNSt3__114basic_iostreamIcNS_11char_traitsIcEEEC2EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE8pubimbueERKNS_6localeE` * `_ZNSt3__114basic_iostreamIcNS_11char_traitsIcEEEC1EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE8in_availEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEEC1EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEPKcmm` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE6sbumpcEv` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE10pubseekoffExNS_8ios_base7seekdirEj` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEEC2EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEErsEPFRS3_S4_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE9sputbackcEw` * `_ZNSt3__112basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEE6__initEPKwm` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sputnEPKwl` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEErsEPFRS3_S4_E` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEEC1EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE9pubsetbufEPwl` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sputcEw` This patch has no effect on Clang based builds. Reviewers: mclow.lists, eugenis, danalbert, jroelofs, EricWF Subscribers: beanz, cfe-commits, mgorny Differential Revision: https://reviews.llvm.org/D24600 llvm-svn: 281681
2016-09-16 08:00:48 +08:00
This macro is used to maintain ABI compatibility for symbols that have been
historically exported by the libc++ library but are now marked inline.
[libc++] Add _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY to support GCC ABI compatibility Summary: GCC and Clang handle visibility attributes on the out-of-line definition of externally instantiated templates differently. For example in the reproducer below Clang will emit both 'foo' and 'bar' with default visibility while GCC only emits a non-hidden 'foo'. ``` // RUN: g++ -std=c++11 -shared -O3 test.cpp && sym_extract.py a.out // RUN: clang++ -std=c++11 -shared -O3 test.cpp && sym_extract.py a.out #define INLINE_VISIBILITY __attribute__((visibility("hidden"), always_inline)) template <class T> struct Foo { void foo(); void bar(); }; template <class T> void Foo<T>::foo() {} template <class T> inline INLINE_VISIBILITY void Foo<T>::bar() {} template struct Foo<int>; ``` This difference creates ABI incompatibilities between Clang and GCC built dylibs. Specifically GCC built dylibs lack definitions for various member functions of `basic_string`, `basic_istream`, `basic_ostream`, `basic_iostream`, and `basic_streambuf` (All of these types are externally instantiated). Surprisingly these missing symbols don't cause many problems because the functions are marked `always_inline` therefore the dylib definition is rarely needed. However when an out-of-line definition is required then GCC built dylibs will fail to link. For example [GCC built dylibs cannot build Clang](http://stackoverflow.com/questions/39454262/clang-build-errors). This patch works around this issue by adding `_LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY` which is used to mark externally instantiated member functions as always inline. When building the library `_LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY` sets the symbol's visibility to "default" instead of "hidden", otherwise it acts exactly the same as `_LIBCPP_INLINE_VISIBILITY`. After applying this patch GCC dylibs now contain: * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE7sungetcEv` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5gbumpEi` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE7sungetcEv` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE9sputbackcEc` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE3getERNS_15basic_streambufIwS2_EE` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEElsEPFRNS_9basic_iosIwS2_EES6_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE4setpEPcS4_` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEEC1EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE6snextcEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE4swapERS3_` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE4swapERS3_` * `_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEPKcm` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEErsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE9pubsetbufEPcl` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE10pubseekoffExNS_8ios_base7seekdirEj` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEErsEPFRNS_9basic_iosIwS2_EES6_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5pbumpEi` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5seekpENS_4fposI11__mbstate_tEE` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE7getlineEPcl` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sgetcEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE3getERNS_15basic_streambufIcS2_EE` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE8in_availEv` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEErsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE6sbumpcEv` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPFRNS_9basic_iosIcS2_EES6_E` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE3getERc` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE6snextcEv` * `_ZNSt3__112basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEE6__initEmw` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE7getlineEPwl` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5tellpEv` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE3getERw` * `_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEmc` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE7pubsyncEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEE3getEPcl` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEEC2EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEErsEPFRNS_9basic_iosIcS2_EES6_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE7pubsyncEv` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sputcEc` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE5seekpExNS_8ios_base7seekdirE` * `_ZNKSt3__115basic_streambufIcNS_11char_traitsIcEEE6getlocEv` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5gbumpEi` * `_ZNSt3__114basic_iostreamIcNS_11char_traitsIcEEE4swapERS3_` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE5seekpENS_4fposI11__mbstate_tEE` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE5tellpEv` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEElsEPFRS3_S4_E` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEE3getEPwl` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEEC2EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPFRS3_S4_E` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE4setgEPcS4_S4_` * `_ZNSt3__112basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEE6__initEPKwmm` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE4setgEPwS4_S4_` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEEC1EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE8pubimbueERKNS_6localeE` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE4swapERS3_` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEEC2EPNS_15basic_streambufIwS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE10pubseekposENS_4fposI11__mbstate_tEEj` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5pbumpEi` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sgetcEv` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEE4swapERS3_` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE10pubseekposENS_4fposI11__mbstate_tEEj` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sputnEPKcl` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5seekpExNS_8ios_base7seekdirE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sgetnEPwl` * `_ZNSt3__113basic_ostreamIwNS_11char_traitsIwEEElsEPFRNS_8ios_baseES5_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE4setpEPwS4_` * `_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sgetnEPcl` * `_ZNKSt3__115basic_streambufIwNS_11char_traitsIwEEE6getlocEv` * `_ZNSt3__114basic_iostreamIcNS_11char_traitsIcEEEC2EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE8pubimbueERKNS_6localeE` * `_ZNSt3__114basic_iostreamIcNS_11char_traitsIcEEEC1EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE8in_availEv` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEEC1EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEPKcmm` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE6sbumpcEv` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE10pubseekoffExNS_8ios_base7seekdirEj` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEEC2EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__113basic_istreamIwNS_11char_traitsIwEEErsEPFRS3_S4_E` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE9sputbackcEw` * `_ZNSt3__112basic_stringIwNS_11char_traitsIwEENS_9allocatorIwEEE6__initEPKwm` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sputnEPKwl` * `_ZNSt3__113basic_istreamIcNS_11char_traitsIcEEErsEPFRS3_S4_E` * `_ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEEC1EPNS_15basic_streambufIcS2_EE` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE9pubsetbufEPwl` * `_ZNSt3__115basic_streambufIwNS_11char_traitsIwEEE5sputcEw` This patch has no effect on Clang based builds. Reviewers: mclow.lists, eugenis, danalbert, jroelofs, EricWF Subscribers: beanz, cfe-commits, mgorny Differential Revision: https://reviews.llvm.org/D24600 llvm-svn: 281681
2016-09-16 08:00:48 +08:00
**_LIBCPP_EXCEPTION_ABI**
Mark the member functions, typeinfo, and vtable of the type as being exported
by the libc++ library. This macro must be applied to all *exception types*.
Exception types should be defined directly in namespace `std` and not the
versioning namespace. This allows throwing and catching some exception types
between libc++ and libstdc++.
Links
=====
* `[cfe-dev] Visibility in libc++ - 1 <http://lists.llvm.org/pipermail/cfe-dev/2013-July/030610.html>`_
* `[cfe-dev] Visibility in libc++ - 2 <http://lists.llvm.org/pipermail/cfe-dev/2013-August/031195.html>`_
* `[libcxx] Visibility fixes for Windows <http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20130805/085461.html>`_