From 0a749081241525dd343a0cdbd964b86816ccacfd Mon Sep 17 00:00:00 2001
From: "Frank Ch. Eigler" <fche@redhat.com>
Date: Thu, 17 Mar 2016 16:04:51 -0400
Subject: [PATCH] dyninst runtime: make ilog2 evaluable even with -O0

While debugging a generated dyninst module, it became an obstacle that
the __builtin_constant_p-guarded ilog2() macro expression failed down
to a ____ilog2_NaN dummy function.  With -O0, that function is at least
referenced, thus blocking linkage.  We ditch the constant-p checking,
and provide an abort()ing fallback.
---
 runtime/dyninst/ilog2.h | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/runtime/dyninst/ilog2.h b/runtime/dyninst/ilog2.h
index a748b8afe..b140d1d03 100644
--- a/runtime/dyninst/ilog2.h
+++ b/runtime/dyninst/ilog2.h
@@ -16,12 +16,6 @@
 #ifndef _STAPDYN_LOG2_H
 #define _STAPDYN_LOG2_H
 
-/*
- * deal with unrepresentable constant logarithms
- */
-extern __attribute__((const, noreturn))
-int ____ilog2_NaN(void);
-
 /**
  * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
  * @n - parameter
@@ -34,8 +28,7 @@ int ____ilog2_NaN(void);
  */
 #define ilog2(n)				\
 (						\
-	__builtin_constant_p(n) ? (		\
-		(n) < 1 ? ____ilog2_NaN() :	\
+		(n) < 1 ? (abort(),-1) :	\
 		(n) & (1ULL << 63) ? 63 :	\
 		(n) & (1ULL << 62) ? 62 :	\
 		(n) & (1ULL << 61) ? 61 :	\
@@ -100,9 +93,7 @@ int ____ilog2_NaN(void);
 		(n) & (1ULL <<  2) ?  2 :	\
 		(n) & (1ULL <<  1) ?  1 :	\
 		(n) & (1ULL <<  0) ?  0 :	\
-		____ilog2_NaN()			\
-				   ) :		\
-	____ilog2_NaN()				\
+		(abort(), -1)        		\
  )
 
 
-- 
2.43.5