[PATCH] G++ static linking on AIX (PR target/26397)

["David Edelsohn" <dje dot gcc at gmail dot com>]

AIX permits static linking against a shared library (without the benefits
of granularity of a normal archive of object files).  When building
libstdc++, some functions are omitted from the shared object that
are included in the static archive.  When linking against shared
libraries, these functions normally are provided by libgcc_s.so.
The combination of -static-libgcc and the libstdc++ shared
library encounter problems on AIX because neither provides
the missing symbols.

On AIX one needs to add libsupc++ when linking statically to
provide the additional symbols for exception handling -- specifically
to rethrow exceptions across library boundaries.

This patch adds a LIBSTDCXX_STATIC macro to cp/g++spec.c
that defaults to the normal "-lstdc++" but is overridden on AIX.
The new macro is used when G++ is invoked with -static or
-static-libgcc.

Okay?

Thanks, David

        PR target/26397
        * g++spec.c (LIBSTDCXX_STATIC): New.
        (lang_spec_driver): Use LIBSTDCXX_STATIC when not shared_libgcc.
        * config/rs6000/aix.h (LIBSTDCXX_STATIC): Define.

Index: cp/g++spec.c
===================================================================
--- cp/g++spec.c        (revision 141264)
+++ cp/g++spec.c        (working copy)
@@ -44,6 +44,9 @@
 #ifndef LIBSTDCXX_PROFILE
 #define LIBSTDCXX_PROFILE LIBSTDCXX
 #endif
+#ifndef LIBSTDCXX_STATIC
+#define LIBSTDCXX_STATIC LIBSTDCXX
+#endif

 void
 lang_specific_driver (int *in_argc, const char *const **in_argv,
@@ -315,7 +318,8 @@
   /* Add `-lstdc++' if we haven't already done so.  */
   if (library > 0)
     {
-      arglist[j] = saw_profile_flag ? LIBSTDCXX_PROFILE : LIBSTDCXX;
+      arglist[j] = shared_libgcc == 0 ? LIBSTDCXX_STATIC
+       : saw_profile_flag ? LIBSTDCXX_PROFILE : LIBSTDCXX;
       if (arglist[j][0] != '-' || arglist[j][1] == 'l')
        added_libraries++;
       j++;
Index: config/rs6000/aix.h
===================================================================
--- config/rs6000/aix.h (revision 141264)
+++ config/rs6000/aix.h (working copy)
@@ -155,6 +155,9 @@
 #define LIB_SPEC "%{pg:-L/lib/profiled -L/usr/lib/profiled}\
 %{p:-L/lib/profiled -L/usr/lib/profiled} %{!shared:%{g*:-lg}} -lc"

+/* Static linking with shared libstdc++ requires libsupc++ as well.  */
+#define LIBSTDCXX_STATIC "-lstdc++ -lsupc++"
+
 /* This now supports a natural alignment mode.  */
 /* AIX word-aligns FP doubles but doubleword-aligns 64-bit ints.  */
 #define ADJUST_FIELD_ALIGN(FIELD, COMPUTED) \