* data.c: Avoid integer truncation in expressions involving floats.

* data.c: Include <intprops.h>.
(arith_driver): When there's an integer overflow in an expression
involving floating point, convert the integers to floating point
so that the resulting value does not suffer from catastrophic
integer truncation.  For example, on a 64-bit host (* 4
most-negative-fixnum 0.5) should yield about -4.6e+18, not zero.
Do not rely on undefined behavior after integer overflow.

1 files changed, 11 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 8bd4426781d..5518531bea8 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,14 @@
+2011-05-21  Paul Eggert  <eggert@cs.ucla.edu>
+
+        * data.c: Avoid integer truncation in expressions involving floats.
+        * data.c: Include <intprops.h>.
+        (arith_driver): When there's an integer overflow in an expression
+        involving floating point, convert the integers to floating point
+        so that the resulting value does not suffer from catastrophic
+        integer truncation.  For example, on a 64-bit host (* 4
+        most-negative-fixnum 0.5) should yield about -4.6e+18, not zero.
+        Do not rely on undefined behavior after integer overflow.
+
 2011-05-20  Paul Eggert  <eggert@cs.ucla.edu>
 
         merge count_size_as_multibyte, parse_str_to_multibyte