From 38656e24bea4a6ced1ebc18a0178bf8c1b175ca7 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sat, 3 May 2014 05:28:46 +0000
Subject: [PATCH] math.c: check domain of base argument

* math.c (math_log): check domain of base argument too.  raises
  Math::DomainError instead of returning NaN if the base is less
  than 0, and returns NaN instead of -infinity if both of two
  arguments are 0.  [ruby-core:62309] [Bug #9797]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45795 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 NEWS                   |  7 +++++++
 math.c                 | 25 +++++++++++++++++--------
 test/ruby/test_math.rb |  2 ++
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/NEWS b/NEWS
index cbe70d0376..a1a5303783 100644
--- a/NEWS
+++ b/NEWS
@@ -48,6 +48,13 @@ with all sufficient information, see the ChangeLog file.
     * When flushing file IO, you cannot assume that the metadata of the file
       is updated immediately.  On some platforms (especially Windows), it is
       delayed until the filesystem load is decreased.
+
+* Math
+  * incompatible changes:
+    * Math.log now raises Math::DomainError instead of returning NaN if the
+      base is less than 0, and returns NaN instead of -infinity if both of
+      two arguments are 0.
+
 * Proc
   * incompatible changes:
     * ArgumentError is no longer raised when lambda Proc is passed as a
diff --git a/math.c b/math.c
index 8a5e5cdc33..70cd26cb07 100644
--- a/math.c
+++ b/math.c
@@ -416,6 +416,8 @@ math_exp(VALUE obj, VALUE x)
 # define log10(x) ((x) < 0.0 ? nan("") : log10(x))
 #endif
 
+static double math_log1(VALUE x);
+
 /*
  *  call-seq:
  *     Math.log(x)          -> Float
@@ -441,10 +443,21 @@ static VALUE
 math_log(int argc, VALUE *argv, VALUE obj)
 {
     VALUE x, base;
-    double d0, d;
-    size_t numbits;
+    double d;
 
     rb_scan_args(argc, argv, "11", &x, &base);
+    d = math_log1(x);
+    if (argc == 2) {
+	d /= math_log1(base);
+    }
+    return DBL2NUM(d);
+}
+
+static double
+math_log1(VALUE x)
+{
+    double d0, d;
+    size_t numbits;
 
     if (RB_BIGNUM_TYPE_P(x) && BIGNUM_POSITIVE_P(x) &&
             DBL_MAX_EXP <= (numbits = rb_absint_numwords(x, 1, NULL))) {
@@ -460,15 +473,11 @@ math_log(int argc, VALUE *argv, VALUE obj)
     /* check for domain error */
     if (d0 < 0.0) domain_error("log");
     /* check for pole error */
-    if (d0 == 0.0) return DBL2NUM(-INFINITY);
+    if (d0 == 0.0) return -INFINITY;
     d = log(d0);
     if (numbits)
         d += numbits * log(2); /* log(2**numbits) */
-    if (argc == 2) {
-	Need_Float(base);
-	d /= log(RFLOAT_VALUE(base));
-    }
-    return DBL2NUM(d);
+    return d;
 }
 
 #ifndef log2
diff --git a/test/ruby/test_math.rb b/test/ruby/test_math.rb
index 74b3940c1d..3383079cc7 100644
--- a/test/ruby/test_math.rb
+++ b/test/ruby/test_math.rb
@@ -142,6 +142,8 @@ class TestMath < Test::Unit::TestCase
     assert_nothing_raised { assert_infinity(-Math.log(-0.0)) }
     assert_raise(Math::DomainError) { Math.log(-1.0) }
     assert_raise(TypeError) { Math.log(1,nil) }
+    assert_raise(Math::DomainError, '[ruby-core:62309] [ruby-Bug #9797]') { Math.log(1.0, -1.0) }
+    assert_nothing_raised { assert_nan(Math.log(0.0, 0.0)) }
   end
 
   def test_log2