ldionne updated this revision to Diff 160873.
ldionne added a comment.
Allow picking a custom default behavior for vendors, per Duncan's comment.
Also, revert to a better name for the macro.
Repository:
rCXX libc++
https://reviews.llvm.org/D50652
Files:
libcxx/CMakeLists.txt
libcxx/docs/BuildingLibcxx.rst
libcxx/docs/DesignDocs/VisibilityMacros.rst
libcxx/include/__config
libcxx/include/__config_site.in
libcxx/utils/libcxx/test/config.py
Index: libcxx/utils/libcxx/test/config.py
===================================================================
--- libcxx/utils/libcxx/test/config.py
+++ libcxx/utils/libcxx/test/config.py
@@ -677,7 +677,8 @@
if feature_macros[m]:
define += '=%s' % (feature_macros[m])
self.cxx.compile_flags += [define]
- if m == '_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS':
+ if m == '_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS' or \
+ m == '_LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT':
continue
if m == '_LIBCPP_ABI_VERSION':
self.config.available_features.add('libcpp-abi-version-v%s'
Index: libcxx/include/__config_site.in
===================================================================
--- libcxx/include/__config_site.in
+++ libcxx/include/__config_site.in
@@ -14,6 +14,7 @@
#cmakedefine _LIBCPP_ABI_UNSTABLE
#cmakedefine _LIBCPP_ABI_FORCE_ITANIUM
#cmakedefine _LIBCPP_ABI_FORCE_MICROSOFT
+#cmakedefine _LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT
#cmakedefine _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
#cmakedefine _LIBCPP_HAS_NO_STDIN
#cmakedefine _LIBCPP_HAS_NO_STDOUT
Index: libcxx/include/__config
===================================================================
--- libcxx/include/__config
+++ libcxx/include/__config
@@ -795,8 +795,20 @@
# define _LIBCPP_INTERNAL_LINKAGE _LIBCPP_ALWAYS_INLINE
#endif
+#ifndef _LIBCPP_HIDE_FROM_ABI_PER_TU
+# ifndef _LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT
+# define _LIBCPP_HIDE_FROM_ABI_PER_TU 0
+# else
+# define _LIBCPP_HIDE_FROM_ABI_PER_TU 1
+# endif
+#endif
+
#ifndef _LIBCPP_HIDE_FROM_ABI
-# define _LIBCPP_HIDE_FROM_ABI _LIBCPP_HIDDEN _LIBCPP_INTERNAL_LINKAGE
+# if _LIBCPP_HIDE_FROM_ABI_PER_TU
+# define _LIBCPP_HIDE_FROM_ABI _LIBCPP_HIDDEN _LIBCPP_INTERNAL_LINKAGE
+# else
+# define _LIBCPP_HIDE_FROM_ABI _LIBCPP_HIDDEN _LIBCPP_ALWAYS_INLINE
+# endif
#endif
#ifdef _LIBCPP_BUILDING_LIBRARY
Index: libcxx/docs/DesignDocs/VisibilityMacros.rst
===================================================================
--- libcxx/docs/DesignDocs/VisibilityMacros.rst
+++ libcxx/docs/DesignDocs/VisibilityMacros.rst
@@ -42,9 +42,7 @@
**_LIBCPP_HIDE_FROM_ABI**
Mark a function as not being part of the ABI of any final linked image that
- uses it, and also as being internal to each TU that uses that function. In
- other words, the address of a function marked with this attribute is not
- guaranteed to be the same across translation units.
+ uses it.
**_LIBCPP_HIDE_FROM_ABI_AFTER_V1**
Mark a function as being hidden from the ABI (per `_LIBCPP_HIDE_FROM_ABI`)
@@ -61,6 +59,41 @@
ABI, we should create a new _LIBCPP_HIDE_FROM_ABI_AFTER_XXX macro, and we can
use it to start removing symbols from the ABI after that stable version.
+**_LIBCPP_HIDE_FROM_ABI_PER_TU**
+ This macro controls whether symbols hidden from the ABI with `_LIBCPP_HIDE_FROM_ABI`
+ are local to each translation unit in addition to being local to each final
+ linked image. This macro is defined to either 0 or 1. When it is defined to
+ 1, translation units compiled with different versions of libc++ can be linked
+ together, since all non ABI-facing functions are local to each translation unit.
+ This allows static archives built with different versions of libc++ to be linked
+ together. This also means that functions marked with `_LIBCPP_HIDE_FROM_ABI`
+ are not guaranteed to have the same address across translation unit boundaries.
+
+ When the macro is defined to 0, there is no guarantee that translation units
+ compiled with different versions of libc++ can interoperate. However, this
+ leads to code size improvements, since non ABI-facing functions can be
+ deduplicated across translation unit boundaries.
+
+ This macro can be defined by users to control the behavior they want from
+ libc++. The default value of this macro (0 or 1) is controlled by whether
+ `_LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT` is defined, which is intended to
+ be used by vendors only (see below).
+
+**_LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT**
+ This macro controls the default value for `_LIBCPP_HIDE_FROM_ABI_PER_TU`.
+ When the macro is defined, per TU ABI insulation is enabled by default, and
+ `_LIBCPP_HIDE_FROM_ABI_PER_TU` is defined to 1 unless overriden by users.
+ Otherwise, per TU ABI insulation is disabled by default, and
+ `_LIBCPP_HIDE_FROM_ABI_PER_TU` is defined to 0 unless overriden by users.
+
+ This macro is intended for vendors to control whether they want to ship
+ libc++ with per TU ABI insulation enabled by default. Users can always
+ control the behavior they want by defining `_LIBCPP_HIDE_FROM_ABI_PER_TU`
+ appropriately.
+
+ By default, this macro is not defined, which means that per TU ABI insulation
+ is not provided unless explicitly overriden by users.
+
**_LIBCPP_TYPE_VIS**
Mark a type's typeinfo, vtable and members as having default visibility.
This attribute cannot be used on class templates.
Index: libcxx/docs/BuildingLibcxx.rst
===================================================================
--- libcxx/docs/BuildingLibcxx.rst
+++ libcxx/docs/BuildingLibcxx.rst
@@ -332,6 +332,15 @@
Use the specified GCC toolchain and standard library when building the native
stdlib benchmark tests.
+.. option:: LIBCXX_HIDE_FROM_ABI_PER_TU_BY_DEFAULT:BOOL
+
+ **Default**: ``OFF``
+
+ Pick the default for whether to constrain ABI-unstable symbols to
+ each individual translation unit. This setting controls whether
+ `_LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT` is defined by default --
+ see the documentation of that macro for details.
+
libc++ ABI Feature Options
--------------------------
Index: libcxx/CMakeLists.txt
===================================================================
--- libcxx/CMakeLists.txt
+++ libcxx/CMakeLists.txt
@@ -120,6 +120,7 @@
option(LIBCXX_ABI_UNSTABLE "Unstable ABI of libc++." OFF)
option(LIBCXX_ABI_FORCE_ITANIUM "Ignore auto-detection and force use of the Itanium ABI.")
option(LIBCXX_ABI_FORCE_MICROSOFT "Ignore auto-detection and force use of the Microsoft ABI.")
+option(LIBCXX_HIDE_FROM_ABI_PER_TU_BY_DEFAULT "Enable per TU ABI insulation by default. To be used by vendors." OFF)
set(LIBCXX_ABI_DEFINES "" CACHE STRING "A semicolon separated list of ABI macros to define in the site config header.")
option(LIBCXX_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF)
@@ -662,6 +663,7 @@
config_define_if(LIBCXX_ABI_UNSTABLE _LIBCPP_ABI_UNSTABLE)
config_define_if(LIBCXX_ABI_FORCE_ITANIUM _LIBCPP_ABI_FORCE_ITANIUM)
config_define_if(LIBCXX_ABI_FORCE_MICROSOFT _LIBCPP_ABI_FORCE_MICROSOFT)
+config_define_if(LIBCXX_HIDE_FROM_ABI_PER_TU_BY_DEFAULT _LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT)
config_define_if_not(LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE)
config_define_if_not(LIBCXX_ENABLE_STDIN _LIBCPP_HAS_NO_STDIN)
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