diff --git a/src/Makefile.am b/src/Makefile.am
index 9a2321ba..442d420d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -269,6 +269,11 @@ endif
 				  $(libunwind_setjmp_la_SOURCES_x86)
 else
 if ARCH_X86_64
+ x86_64_gen_offsets_SOURCES = x86_64/gen-offsets.c
+ noinst_PROGRAMS = x86_64/gen-offsets
+ BUILT_SOURCES = _ucontext_i.h
+_ucontext_i.h: x86_64/gen-offsets
+	x86_64/gen-offsets > $@
  lib_LTLIBRARIES_arch = libunwind-x86_64.la
  libunwind_la_SOURCES = $(libunwind_la_SOURCES_x86_64)
  libunwind_x86_64_la_SOURCES = $(libunwind_x86_64_la_SOURCES_x86_64)
diff --git a/src/x86_64/gen-offsets.c b/src/x86_64/gen-offsets.c
index 343716db..72383b69 100644
--- a/src/x86_64/gen-offsets.c
+++ b/src/x86_64/gen-offsets.c
@@ -4,23 +4,6 @@
 
 #define REG_OFFSET(reg) (offsetof(struct ucontext, uc_mcontext.gregs[REG_##reg]))
 
-# define REG_R8		0
-# define REG_R9		1
-# define REG_R10	2
-# define REG_R11	3
-# define REG_R12	4
-# define REG_R13	5
-# define REG_R14	6
-# define REG_R15	7
-# define REG_RDI	8
-# define REG_RSI	9
-# define REG_RBP	10
-# define REG_RBX	11
-# define REG_RDX	12
-# define REG_RAX	13
-# define REG_RCX	14
-# define REG_RSP	15
-# define REG_RIP	16
 
 char *regs[] = { "RAX",
 	"RBX",
@@ -43,31 +26,34 @@ char *regs[] = { "RAX",
 
 main()
 {
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[0], REG_OFFSET(RAX));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[1], REG_OFFSET(RBX));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[2], REG_OFFSET(RCX));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[3], REG_OFFSET(RDX));
+	printf("#ifndef UCONTEXT_I_H\n#define UCONTEXT_I_H\n");
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[0], REG_OFFSET(RAX));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[1], REG_OFFSET(RBX));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[2], REG_OFFSET(RCX));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[3], REG_OFFSET(RDX));
 
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[4], REG_OFFSET(RDI));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[5], REG_OFFSET(RSI));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[6], REG_OFFSET(RSP));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[7], REG_OFFSET(RBP));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[4], REG_OFFSET(RDI));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[5], REG_OFFSET(RSI));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[6], REG_OFFSET(RSP));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[7], REG_OFFSET(RBP));
 
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[8], REG_OFFSET(R8));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[9], REG_OFFSET(R9));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[10], REG_OFFSET(R10));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[11], REG_OFFSET(R11));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[8], REG_OFFSET(R8));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[9], REG_OFFSET(R9));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[10], REG_OFFSET(R10));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[11], REG_OFFSET(R11));
 
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[12], REG_OFFSET(R12));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[13], REG_OFFSET(R13));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[14], REG_OFFSET(R14));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[15], REG_OFFSET(R15));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[15], REG_OFFSET(R15));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[15], REG_OFFSET(R15));
-	printf("#define REG_OFFSET_%s\t%d\n" , regs[16], REG_OFFSET(RIP));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[12], REG_OFFSET(R12));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[13], REG_OFFSET(R13));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[14], REG_OFFSET(R14));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[15], REG_OFFSET(R15));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[15], REG_OFFSET(R15));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[15], REG_OFFSET(R15));
+	printf("#define REG_OFFSET_%s\t%ld\n" , regs[16], REG_OFFSET(RIP));
 
-	printf("#define REG_OFFSET_FPREGS_PTR\t%d\n" , offsetof(struct ucontext, uc_mcontext.fpregs));
-	printf("#define FPREG_OFFSET_MXCR\t%d\n" , offsetof(struct _libc_fpstate, mxcsr));
+	printf("#define REG_OFFSET_FPREGS_PTR\t%ld\n" , offsetof(struct ucontext, uc_mcontext.fpregs));
+	printf("#define FPREG_OFFSET_MXCR\t%ld\n" , offsetof(struct _libc_fpstate, mxcsr));
+	printf("#endif /* UCONTEXT_I_H */\n");
+	return 0;
 }
 
 
diff --git a/src/x86_64/setcontext.S b/src/x86_64/setcontext.S
index d1578e1d..f5fd5521 100644
--- a/src/x86_64/setcontext.S
+++ b/src/x86_64/setcontext.S
@@ -23,27 +23,7 @@ LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 
-#define REG_OFFSET_RAX  144
-#define REG_OFFSET_RBX  128
-#define REG_OFFSET_RCX  152
-#define REG_OFFSET_RDX  136
-#define REG_OFFSET_RDI  104
-#define REG_OFFSET_RSI  112
-#define REG_OFFSET_RSP  160
-#define REG_OFFSET_RBP  120
-#define REG_OFFSET_R8   40
-#define REG_OFFSET_R9   48
-#define REG_OFFSET_R10  56
-#define REG_OFFSET_R11  64
-#define REG_OFFSET_R12  72
-#define REG_OFFSET_R13  80
-#define REG_OFFSET_R14  88
-#define REG_OFFSET_R15  96
-#define REG_OFFSET_R15  96
-#define REG_OFFSET_R15  96
-#define REG_OFFSET_RIP  168
-#define REG_OFFSET_FPREGS_PTR   224
-#define FPREG_OFFSET_MXCR       24
+#include "_ucontext_i.h"
 
 	.global _x86_64_setcontext