X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcold%2Fsnapshot.lisp;h=a52d1ca5c07f5fdb86f96566d59096e48c0d5151;hb=91392754bf1d241cd6913c728268caf18eae1485;hp=846c06f73cca8fb31c933025518f474c03812ca3;hpb=d40a76606c86722b0aef8179155f9f2840739b72;p=sbcl.git

diff --git a/src/cold/snapshot.lisp b/src/cold/snapshot.lisp
index 846c06f..a52d1ca 100644
--- a/src/cold/snapshot.lisp
+++ b/src/cold/snapshot.lisp
@@ -1,4 +1,23 @@
 ;;;; code to detect whether a package has changed
+;;;;
+;;;; This is really old code which was most useful when first
+;;;; bootstrapping SBCL when only CMU CL was available as an XC host.
+;;;; Its main purpose was to check that legacy code like DEFMACRO
+;;;; DOLIST and DEFUN IR1-OPTIMIZE-UNTIL-DONE was all correctly
+;;;; converted from code which mutated the XC host into code which
+;;;; built things for the target.
+;;;;
+;;;; These days, things like DEFUN IR1-OPTIMIZE-UNTIL-DONE can't very
+;;;; well be mutating the cross-compiler host because we can build
+;;;; successfully under OpenMCL, which shouldn't have the same
+;;;; packages or symbols. So we don't need to worry very much about
+;;;; modifying the XC host's private packages. However, it's still
+;;;; conceivable that something affecting the XC host's CL package
+;;;; (maybe DEFMACRO DOLIST?) could be written in such a way that it
+;;;; would silently compile under SBCL, CMU CL, and even OpenMCL, and
+;;;; still be fundamentally wrong. Since it'd be good to prevent such
+;;;; modifications of the XC host's CL package, this code is still
+;;;; retained despite being a little strange.
 
 ;;;; This software is part of the SBCL system. See the README file for
 ;;;; more information.