re PR c++/9283 (__attribute__((visibility ("hidden"))) not supported for class/struct)

	PR c++/9283
	PR c++/15000
	* c-common.c (c_common_attribute_table): Allow
	handle_visibility_attribute to be called for types.
	(handle_visibility_attribute) When given a type, set the visibility
	bits on the TYPE_NAME.  When given a decl, don't set no_add_attrs
	so that we can check later whether the attribute was present. Added
	warning if attribute applied to non class type.
	* c-decl.c (diagnose_mismatched_decls): Updated rules for merging
	decls and checking that they are consistent.
	* common.opt: Added -fvisibility.
	* c.opt, c-opts.c: Added -fvisibility-inlines-hidden.
	* c-pragma.h, c-pragma.c: Added handle_pragma_visibility().
	* flags.h, tree.h: Added assorted support defines for overall patch
	* opts.c: Added parsing support for -fvisibility.
	* tree.c (build_decl): Set visibility for all decls to be whatever
	is in force at that time.
	* varasm.c (default_binds_local_p_1): Reworked logic determining
	when to make a symbol locally bound.
	* doc/invoke.texi: Added documentation for -fvisibility and
	-fvisibility-inlines-hidden.

	PR c++/15000
	PR c++/9283
	* class.c (check_field_decls): Apply hidden visibility if
	-fvisibility-inlines-hidden and inlined unless otherwise specified
	(build_vtable): Set vtable visibility to class visibility.
	(check_field_decls): Default static member visibility to class
	visibility.
	(check_methods): Default method visibility to class visibility.
	* cp-tree.h: Added CLASSTYPE_VISIBILITY and
	CLASSTYPE_VISIBILITY_SPECIFIED macro.
	* decl.c (duplicate_decls): New logic for merging definition decls
	with declaration decls. Added ignore & warning when non default
	applied to global operator new or delete.
	* method.c, optimize.c, rtti.c: Added setting of VISIBILITY_SPECIFIED
	wherever VISIBILITY was changed
	* rtti.c (get_tinfo_decl): Set typeinfo visibility to class
	visibility.
	(tinfo_base_init): Set typeinfo name visibility to class visibility.

	PR c++/9283
	PR c++/15000
	* gcc.dg/visibility-9.c, gcc.dg/visibility-a.c: New tests.
	* g++.dg/ext/visibility/: New directory.
	* g++.dg/ext/visibility-1.C, g++.dg/ext/visibility-2.C
	g++.dg/ext/visibility-3.C, g++.dg/ext/visibility-4.C,
	g++.dg/ext/visibility-5.C, g++.dg/ext/visibility-6.C,
	g++.dg/ext/visibility-7.C: Move to g++.dg/ext/visibility/.
	* g++.dg/ext/visibility/fvisibility.C,
	g++.dg/ext/visibility/fvisibility-inlines-hidden.C,
	g++.dg/ext/visibility/fvisibility-override1.C
	g++.dg/ext/visibility/fvisibility-override2.C
	g++.dg/ext/visibility/memfuncts.C
	g++.dg/ext/visibility/noPLT.C
	g++.dg/ext/visibility/pragma.C
	g++.dg/ext/visibility/pragma-override1.C
	g++.dg/ext/visibility/pragma-override2.C
	g++.dg/ext/visibility/staticmemfuncts.C
	g++.dg/ext/visibility/virtual.C: New tests.

Co-Authored-By: Brian Ryner <bryner@brianryner.com>

From-SVN: r85167

1 files changed, 66 insertions, 2 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index efd20a9..2dc6969 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -182,7 +182,8 @@ in the following sections.
 -fno-optional-diags  -fpermissive @gol
 -frepo  -fno-rtti  -fstats  -ftemplate-depth-@var{n} @gol
 -fuse-cxa-atexit  -fno-weak  -nostdinc++ @gol
--fno-default-inline  -Wabi  -Wctor-dtor-privacy @gol
+-fno-default-inline  -fvisibility-inlines-hidden @gol
+-Wabi  -Wctor-dtor-privacy @gol
 -Wnon-virtual-dtor  -Wreorder @gol
 -Weffc++  -Wno-deprecated @gol
 -Wno-non-template-friend  -Wold-style-cast @gol
@@ -696,7 +697,8 @@ See S/390 and zSeries Options.
 -fargument-alias  -fargument-noalias @gol
 -fargument-noalias-global  -fleading-underscore @gol
 -ftls-model=@var{model} @gol
--ftrapv  -fwrapv  -fbounds-check}
+-ftrapv  -fwrapv  -fbounds-check @gol
+-fvisibility}
 @end table
 
 @menu
@@ -1457,6 +1459,20 @@ This option is required for fully standards-compliant handling of static
 destructors, but will only work if your C library supports
 @code{__cxa_atexit}.
 
+@item -fvisibility-inlines-hidden
+@opindex fvisibility-inlines-hidden
+Causes all inlined methods to be marked with
+@code{__attribute__ ((visibility ("hidden")))} so that they do not
+appear in the export table of a DSO and do not require a PLT indirection
+when used within the DSO. Enabling this option can have a dramatic effect
+on load and link times of a DSO as it massively reduces the size of the
+dynamic export table when the library makes heavy use of templates. While
+it can cause bloating through duplication of code within each DSO where
+it is used, often the wastage is less than the considerable space occupied
+by a long symbol name in the export table which is typical when using
+templates and namespaces. For even more savings, combine with the
+@code{-fvisibility=hidden} switch.
+
 @item -fno-weak
 @opindex fno-weak
 Do not use weak symbol support, even if it is provided by the linker.
@@ -11630,6 +11646,54 @@ The @var{model} argument should be one of @code{global-dynamic},
 
 The default without @option{-fpic} is @code{initial-exec}; with
 @option{-fpic} the default is @code{global-dynamic}.
+
+@item -fvisibility=@var{default|internal|hidden|protected}
+@opindex fvisibility
+Set the default ELF image symbol visibility to the specified option - all
+symbols will be marked with this unless overrided within the code.
+Using this feature can very substantially improve linking and
+load times of shared object libraries, produce more optimised
+code, provide near-perfect API export and prevent symbol clashes.
+It is @strong{strongly} recommended that you use this in any shared objects
+you distribute.
+     
+Despite the nomenclature, @code{default} always means public ie;
+available to be linked against from outside the shared object.
+@code{protected} and @code{internal} are pretty useless in real-world
+usage so the only other commonly used option will be @code{hidden}.
+The default if -fvisibility isn't specified is @code{default} ie; make every
+symbol public - this causes the same behaviour as previous versions of
+GCC.
+     
+A good explanation of the benefits offered by ensuring ELF
+symbols have the correct visibility is given by ``How To Write
+Shared Libraries'' by Ulrich Drepper (which can be found at
+@w{@uref{http://people.redhat.com/~drepper/}}) - however a superior
+solution made possible by this option to marking things hidden when
+the default is public is to make the default hidden and mark things
+public. This is the norm with DLL's on Windows and with @option{-fvisibility=hidden}
+and @code{__attribute__ ((visibility("default")))} instead of
+@code{__declspec(dllexport)} you get almost identical semantics with
+identical syntax. This is a great boon to those working with
+cross-platform projects.
+
+For those adding visibility support to existing code, you may find
+@samp{#pragma GCC visibility} of use. This works by you enclosing
+the declarations you wish to set visibility for with (for example)
+@samp{#pragma GCC visibility push(hidden)} and
+@samp{#pragma GCC visibility pop}. These can be nested up to sixteen
+times. Bear in mind that symbol visibility should be viewed @strong{as
+part of the API interface contract} and thus all new code should
+always specify visibility when it is not the default ie; declarations
+only for use within the local DSO should @strong{always} be marked explicitly
+as hidden as so to avoid PLT indirection overheads - making this
+abundantly clear also aids readability and self-documentation of the code.
+Note that due to ISO C++ specification requirements, operator new and
+operator delete must always be of default visibility.
+
+An overview of these techniques, their benefits and how to use them
+is at @w{@uref{http://www.nedprod.com/programs/gccvisibility.html}}.
+
 @end table
 
 @c man end