From 98c9af500125df41fdb46d7e384b00982d72493a Mon Sep 17 00:00:00 2001
From: Rich Felker
Date: Sat, 5 May 2012 22:22:46 -0400
Subject: fix definitions of FP_ILOGB constants
two issues: (1) the type was wrong (unsigned instead of signed int),
and (2) the value of FP_ILOGBNAN should be INT_MIN rather than INT_MAX
to match the ABI. this is also much more useful since INT_MAX
corresponds to a valid input (infinity). the standard would allow us
to set FP_ILOGB0 to -INT_MAX instead of INT_MIN, which would give us
distinct values for ilogb(0) and ilogb(NAN), but the benefit seems way
too small to justify ignoring the ABI.
note that the macro is just a "portable" (to any twos complement
system where signed and unsigned int have the same width) way to write
INT_MIN without needing limits.h. it's valid to use this method since
these macros are not required to work in #if directives.
---
include/math.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
(limited to 'include')
diff --git a/include/math.h b/include/math.h
index d4359f32..61738e6a 100644
--- a/include/math.h
+++ b/include/math.h
@@ -28,8 +28,8 @@ extern "C" {
#define MATH_ERREXCEPT 2
#define math_errhandling 2
-#define FP_ILOGBNAN (((unsigned)-1)>>1)
-#define FP_ILOGB0 (~FP_ILOGBNAN)
+#define FP_ILOGBNAN (-1-(int)(((unsigned)-1)>>1))
+#define FP_ILOGB0 FP_ILOGBNAN
#define FP_NAN 0
#define FP_INFINITE 1
--
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