0.8.6.28:

Fix for WTF bug on #lisp IRC
	... adjust the EXPT derive-type logic to be more correct.
	Text adjustments
	... refer to base-target-features.lisp-expr in INSTALL
	... add our newline back after the first line of the banner (I
		hope without breaking gcc3.3 in the process...)

INSTALL

@@ -133,10 +133,12 @@ To build the system binaries:
      where it can be found.
   3. If you like, you can tweak the *FEATURES* set for the resulting
      Lisp system, enabling or disabling features like documentation
-     strings or extra debugging code. The preferred way to do this is
-     by creating a file "customize-target-features.lisp", containing
-     a lambda expression which is applied to the default *FEATURES*
-     set and which returns the new *FEATURES* set, e.g.
+     strings, threads, or extra debugging code (see
+     "base-target-features.lisp-expr" for a list of recognized
+     *FEATURES*).  The preferred way to do this is by creating a file
+     "customize-target-features.lisp", containing a lambda expression
+     which is applied to the default *FEATURES* set and which returns
+     the new *FEATURES* set, e.g.
 	(LAMBDA (LIST)
 	  (ADJOIN :SB-SHOW
 		  (REMOVE :SB-DOC

src/compiler/float-tran.lisp

@@ -906,17 +906,21 @@
 	((csubtypep y (specifier-type 'integer))
 	 ;; A real raised to an integer power is well-defined.
 	 (merged-interval-expt x y))
+	;; A real raised to a non-integral power can be a float or a
+	;; complex number.
+	((or (csubtypep x (specifier-type '(rational 0)))
+	     (csubtypep x (specifier-type '(float (0d0)))))
+	 ;; But a positive real to any power is well-defined.
+	 (merged-interval-expt x y))
+	((and (csubtypep x (specifier-type 'rational))
+	      (csubtypep x (specifier-type 'rational)))
+	 ;; A rational to the power of a rational could be a rational
+	 ;; or a possibly-complex single float
+	 (specifier-type '(or rational single-float (complex single-float))))
 	(t
-	 ;; A real raised to a non-integral power can be a float or a
-	 ;; complex number.
-	 (cond ((or (csubtypep x (specifier-type '(rational 0)))
-		    (csubtypep x (specifier-type '(float (0d0)))))
-		;; But a positive real to any power is well-defined.
-		(merged-interval-expt x y))
-	       (t
-		;; a real to some power. The result could be a real
-		;; or a complex.
-		(float-or-complex-float-type (numeric-contagion x y)))))))
+	 ;; a real to some power. The result could be a real or a
+	 ;; complex.
+	 (float-or-complex-float-type (numeric-contagion x y)))))
 
 (defoptimizer (expt derive-type) ((x y))
   (two-arg-derive-type x y #'expt-derive-type-aux #'expt))

src/runtime/runtime.c

@@ -166,6 +166,7 @@ print_banner()
 {
     printf(
 "This is SBCL %s, an implementation of ANSI Common Lisp.\n\
+\n\
 More information about SBCL is available at <http://www.sbcl.org/>.\
 \n\
 SBCL is free software, provided as is, with absolutely no warranty.\n\

tests/compiler.impure.lisp

@@ -865,7 +865,12 @@
     (load source)
     (full-check)
     (delete-file fasl)))
-
+
+(defun expt-derive-type-bug (a b)
+  (unless (< a b)
+    (truncate (expt a b))))
+(assert (equal (multiple-value-list (expt-derive-type-bug 1 1))
+	       '(1 0)))
 
 ;;;; tests not in the problem domain, but of the consistency of the
 ;;;; compiler machinery itself

version.lisp-expr

@@ -17,4 +17,4 @@
 ;;; checkins which aren't released. (And occasionally for internal
 ;;; versions, especially for internal versions off the main CVS
 ;;; branch, it gets hairier, e.g. "0.pre7.14.flaky4.13".)
-"0.8.6.27"
+"0.8.6.28"