From c810fcea1fa7983ef5bcabe6556cdc19dde6dd8d Mon Sep 17 00:00:00 2001
From: Jason Evans <jasone@canonware.com>
Date: Wed, 4 Feb 2015 16:41:55 -0800
Subject: Add (x != 0) assertion to lg_floor(x).

lg_floor(0) is undefined, but depending on compiler options may not
cause a crash.  This assertion makes it harder to accidentally abuse
lg_floor().
---
 include/jemalloc/internal/util.h | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/include/jemalloc/internal/util.h b/include/jemalloc/internal/util.h
index b2b4ab7..5ad4933 100644
--- a/include/jemalloc/internal/util.h
+++ b/include/jemalloc/internal/util.h
@@ -136,14 +136,14 @@ JEMALLOC_ALWAYS_INLINE int
 jemalloc_ffsl(long bitmap)
 {
 
-        return (JEMALLOC_INTERNAL_FFSL(bitmap));
+	return (JEMALLOC_INTERNAL_FFSL(bitmap));
 }
 
 JEMALLOC_ALWAYS_INLINE int
 jemalloc_ffs(int bitmap)
 {
 
-        return (JEMALLOC_INTERNAL_FFS(bitmap));
+	return (JEMALLOC_INTERNAL_FFS(bitmap));
 }
 
 /* Compute the smallest power of 2 that is >= x. */
@@ -170,6 +170,8 @@ lg_floor(size_t x)
 {
 	size_t ret;
 
+	assert(x != 0);
+
 	asm ("bsr %1, %0"
 	    : "=r"(ret) // Outputs.
 	    : "r"(x)    // Inputs.
@@ -180,22 +182,26 @@ lg_floor(size_t x)
 JEMALLOC_INLINE size_t
 lg_floor(size_t x)
 {
-    unsigned long ret;
+	unsigned long ret;
+
+	assert(x != 0);
 
 #if (LG_SIZEOF_PTR == 3)
-    _BitScanReverse64(&ret, x);
+	_BitScanReverse64(&ret, x);
 #elif (LG_SIZEOF_PTR == 2)
-    _BitScanReverse(&ret, x);
+	_BitScanReverse(&ret, x);
 #else
 #  error "Unsupported type sizes for lg_floor()"
 #endif
-    return (ret);
+	return (ret);
 }
 #elif (defined(JEMALLOC_HAVE_BUILTIN_CLZ))
 JEMALLOC_INLINE size_t
 lg_floor(size_t x)
 {
 
+	assert(x != 0);
+
 #if (LG_SIZEOF_PTR == LG_SIZEOF_INT)
 	return (((8 << LG_SIZEOF_PTR) - 1) - __builtin_clz(x));
 #elif (LG_SIZEOF_PTR == LG_SIZEOF_LONG)
@@ -209,6 +215,8 @@ JEMALLOC_INLINE size_t
 lg_floor(size_t x)
 {
 
+	assert(x != 0);
+
 	x |= (x >> 1);
 	x |= (x >> 2);
 	x |= (x >> 4);
-- 
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