[PATCH/RFC] ia64: fix strict aliasing warnings with ENTRY_POINT

[Mike Frysinger <vapier@gentoo.org>]

Function pointers on ia64 are like parisc -- they're plabels.  While
the parisc port enjoys a gcc builtin for extracting the address here,
ia64 has no such luck.

Casting & dereferencing in one go triggers a strict aliasing warning.
Use a union to fix that.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
 ports/ChangeLog.ia64       |  4 ++++
 ports/sysdeps/ia64/entry.h | 12 ++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/ports/ChangeLog.ia64 b/ports/ChangeLog.ia64
index 46e2dd9..fec4f40 100644
--- a/ports/ChangeLog.ia64
+++ b/ports/ChangeLog.ia64
@@ -1,5 +1,9 @@
 2013-03-10  Mike Frysinger  <vapier@gentoo.org>
 
+	* sysdeps/ia64/entry.h (ENTRY_POINT): Change to a union.
+
+2013-03-10  Mike Frysinger  <vapier@gentoo.org>
+
 	* sysdeps/unix/sysv/linux/ia64/nptl/dl-sysdep.h:
 	Change multiple inclusion guard to _LINUX_IA64_DL_SYSDEP_H.
 	Use #include_next.
diff --git a/ports/sysdeps/ia64/entry.h b/ports/sysdeps/ia64/entry.h
index b93e1b6..36f35a6 100644
--- a/ports/sysdeps/ia64/entry.h
+++ b/ports/sysdeps/ia64/entry.h
@@ -3,8 +3,16 @@ extern void _start (void);
 #endif
 
 /* The function's entry point is stored in the first word of the
-   function descriptor (plabel) of _start().  */
-#define ENTRY_POINT (((long int *) _start)[0])
+   function descriptor (plabel) of _start().  Get tricky to avoid
+   strict aliasing warnings.  */
+#define ENTRY_POINT \
+  ({ union { \
+       void *_start; \
+       long int *_ints; \
+     } _u; \
+     _u._start = _start; \
+     _u._ints[0]; \
+  })
 
 /* We have to provide a special declaration.  */
 #define ENTRY_POINT_DECL(class) class void _start (void);
-- 
1.8.1.2