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-rw-r--r--include/shlib-compat.h82
1 files changed, 39 insertions, 43 deletions
diff --git a/include/shlib-compat.h b/include/shlib-compat.h
index b874e2588f..537851d753 100644
--- a/include/shlib-compat.h
+++ b/include/shlib-compat.h
@@ -62,6 +62,20 @@
    i.e. either GLIBC_2.1 or the "earliest version" specified in
    shlib-versions if that is newer.  */
 
+/* versioned_symbol (LIB, LOCAL, SYMBOL, VERSION) emits a definition
+   of SYMBOL with a default (@@) VERSION appropriate for LIB.  (The
+   actually emitted symbol version is adjusted according to the
+   baseline symbol version for LIB.)  The address of the symbol is
+   taken from LOCAL.  Properties of LOCAL are copied to the exported
+   symbol.  In particular, LOCAL itself should be global.  It is
+   unspecified whether SYMBOL@VERSION is associated with LOCAL, or if
+   an intermediate alias is created.  If LOCAL and SYMBOL are
+   distinct, and LOCAL is also intended for export, its version should
+   be specified explicitly with versioned_symbol, too.
+
+   If LOCAL is a data symbol and does not have a non-zero initializer,
+   it should be defined with __attribute__ ((nocommon)) for
+   compatibility with GCC versions that default to -fcommon.  */
 # define versioned_symbol(lib, local, symbol, version) \
   versioned_symbol_1 (lib, local, symbol, version)
 # define versioned_symbol_1(lib, local, symbol, version) \
@@ -69,44 +83,25 @@
 # define versioned_symbol_2(local, symbol, name) \
   default_symbol_version (local, symbol, name)
 
+/* compat_symbol is like versioned_symbol, but emits a compatibility
+   version (with @ instead of @@).  The same issue related to
+   intermediate aliases applies, so LOCAL should not be listed in the
+   Versions file, or otherwise it can be exported with an undesired
+   default symbol version.  */
 # define compat_symbol(lib, local, symbol, version) \
-  compat_symbol_reference (lib, local, symbol, version)
-
-/* This is similar to compat_symbol, but allows versioning the same symbol
-   to multiple version without having multiple symbol definitions.  For
-   instance:
-
-   #if (SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_2))
-   compat_symbol_unique (libc, old_foo, GLIBC_2_1_2)
-   #endif
-
-   #if (SHLIB_COMPAT (libpthread, GLIBC_2_2_6, GLIBC_2_3))
-   compat_symbol_unique (libc, old_foo, GLIBC_2_2_6)
-   #endif
-
-   Internally it creates a unique strong alias to the input symbol and
-   creates one compat_symbol on the alias.  Using the above example,
-   it is similar to:
-
-   #if (SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_2))
-   strong_alias (old_foo, old_foo__COUNTER__)
-   compat_symbol (libc, old_foo__COUNTER__, foo, GLIBC_2_2)
-   #endif.
-
-   With __COUNTER__ being a monotonic number generated by the compiler.  */
-
-# define __compat_symbol_unique_concat(x, y) x ## y
-# define _compat_symbol_unique_concat(x, y) \
-  __compat_symbol_unique_concat (x, y)
-# define _compat_symbol_unique_alias(name) \
-  _compat_symbol_unique_concat (name, __COUNTER__)
-# define _compat_symbol_unique(lib, orig_name, name, version) \
-  strong_alias (orig_name, name) \
-  compat_symbol (lib, name, orig_name, version)
-# define compat_symbol_unique(lib, name, version) \
-  _compat_symbol_unique (lib, name, _compat_symbol_unique_alias (name), \
-                         version)
-
+  compat_symbol_1 (lib, local, symbol, version)
+# define compat_symbol_1(lib, local, symbol, version) \
+  compat_symbol_2 (local, symbol, VERSION_##lib##_##version)
+/* See <libc-symver.h>.  */
+# ifdef __ASSEMBLER__
+#define compat_symbol_2(local, symbol, name) \
+  _set_symbol_version (local, symbol@name)
+# else
+#  define compat_symbol_2(local, symbol, name) \
+  compat_symbol_3 (local, symbol, name)
+#  define compat_symbol_3(local, symbol, name) \
+  _set_symbol_version (local, #symbol "@" #name)
+# endif
 #else
 
 /* Not compiling ELF shared libraries at all, so never any old versions.  */
@@ -118,16 +113,17 @@
 
 /* This should not appear outside `#if SHLIB_COMPAT (...)'.  */
 # define compat_symbol(lib, local, symbol, version) ...
-# define compat_symbol_unique(lib, name, version) ...
 
 #endif
 
 /* Use compat_symbol_reference for a reference *or* definition of a
-   specific version of a symbol.  Definitions are primarily used to
-   ensure tests reference the exact compat symbol required, or define an
-   interposing symbol of the right version e.g. __malloc_initialize_hook
-   in mcheck-init.c.  Use compat_symbol to define such a symbol within
-   the shared libraries that are built for users.  */
+   specific version of a symbol.  compat_symbol_reference does not
+   create intermediate aliases.  Definitions are primarily used to
+   ensure tests reference the exact compat symbol required, or define
+   an interposing symbol of the right version e.g.,
+   __malloc_initialize_hook in mcheck-init.c.  Use compat_symbol to
+   define such a symbol within the shared libraries that are built for
+   users.  */
 #define compat_symbol_reference(lib, local, symbol, version) \
   compat_symbol_reference_1 (lib, local, symbol, version)
 #define compat_symbol_reference_1(lib, local, symbol, version) \