On 30/11/19 22:13 +0100, Jan Hubicka wrote:
Hi,
this is patch incorporating (I hope) all the suggestions and corrections
which I applied. I will work incremnetaly on supporting the name@@@node
semantics which is bit different from @ and @@ one by actually removing
the original symbol. Here I need to change assembler name of the symbol
itself but then I still need an alternative assembler name for the local
use. This is bit like weakref rewriting but not quite and it seems it is
better to do that incrementally.
It would be great to convert libstdc++ to the new infrastructure so it
becomes LTO safe and gives some real world testing to this
infrastructure. I tried that but found it is bit non-trivial since
currently way we need to attach the attribute to definition itself,
while current .symver output is done in separate C++ files.
I will add it to my TODO list.
Index: doc/extend.texi
===================================================================
--- doc/extend.texi (revision 278877)
+++ doc/extend.texi (working copy)
@@ -3711,6 +3711,41 @@ Function Attributes}, @ref{PowerPC Funct
@ref{Nios II Function Attributes}, and @ref{S/390 Function Attributes}
for details.
+@item symver ("@var{name2}@@@var{nodename}")
+On ELF targets this attribute creates a symbol version. The @var{name2} part
+of the parameter is the actual name of the symbol by which it will be
+externally referenced. The @code{nodename} portion should be the name of a
+node specified in the version script supplied to the linker when building a
+shared library. Versioned symbol must be defined and must be exported with
I think this should be either "A versioned symbol" or "Versioned
symbols".
+default visibility.
+
+@smallexample
+__attribute__ ((__symver__ ("foo@@VERS_1"))) int
+foo_v1 (void)
+@{
+@}
+@end smallexample
+
+Will produce a @code{.symver foo_v1, foo@@VERS_1} directive in the assembler
+output.
+
+It's an error to define multiple version of a given symbol. In such case
"In such cases"
+an alias can be used.
+
+@smallexample
+__attribute__ ((__symver__ ("foo@@VERS_2")))
+__attribute__ ((alias ("foo_v1")))
+int symver_foo_v1 (void);
+@end smallexample
+
+This example creates an alias of @code{foo_v1} with symbol name
+@code{symver_foo_v1} which will be version @code{VERS_2} of @code{foo}.
+
+Finally if the parameter is @code{"@var{name2}@@@@@var{nodename}"} then in
+addition to creating a symbol version (as if
+@code{"@var{name2}@@@var{nodename}"} was used) the version will be also used
s/was used/had been used/
s/will be also used/will also be used/
