[ruby-talk:19602] Overriding Marshal.load version test

Evolving Marshal versions have given me headaches, and today I found out
from IRC that "I'm not the only".

So I wrote this small modification which should be backwards compatible
(in a sense older programs should continue to work, assuming people
haven't overwritten their Marshal.load).

I'd like to see discussion whether this patch should be incorporated.

     - Aleksi



The method signature changes a bit, first old, and then newer:

[aleksi@dogma ruby-1.6.4]$ ri Marshal.load
---------------------------------------------------------- Marshal::load
     load( from [, aProc] ) -> anObject
------------------------------------------------------------------------
     Returns the result of converting the serialized data in from into a
     Ruby object (possibly with associated subordinate objects). from
     may be either an instance of IO or an object that responds to
     to_str. If proc is specified, it will be passed each object as it
     is deserialized.

[aleksi@dogma ruby-2001-08-12]$ ri Marshal.load
---------------------------------------------------------- Marshal::load
     load( from [, aProc [, override]] ) -> anObject
------------------------------------------------------------------------
     Returns the result of converting the serialized data in from into a
     Ruby object (possibly with associated subordinate objects). from
     may be either an instance of IO or an object that responds to
     to_str. If proc is specified, it will be passed each object as it
     is deserialized. If override is given with non-false value the
     test whether loader version is compatible with marshaller which
     produced from is skipped. Warning: skipping the test might crash
     the entire interpreter.

An example:

[aleksi@dogma ruby-2001-08-12]$ ./ruby -ve 
'File.open("data.dat","wb") do |f| Marshal.dump("foo", f); end;'
ruby 1.7.1 (2001-08-06) [i686-linux]

[aleksi@dogma ruby-2001-08-12]$ cat data.dat 
foo

[aleksi@dogma ruby-2001-08-12]$ ../ruby-1.6.4/ruby -ve
'File.open("data.dat") |f| p Marshal.load(f); end;'
ruby 1.6.4 (2001-06-04) [i686-linux]
-e:1:in `load': incompatible marshal file format (can't be
read) (TypeError)
	format version 4.5 required; 4.6 given
	from -e:1
	from -e:1:in `open'
	from -e:1

[aleksi@dogma ruby-2001-08-12]$ ../ruby-1.6.4/ruby -ve
'File.open("data.dat") do |f| p Marshal.load(f,nil,true); end;'
ruby 1.6.4 (2001-06-04) [i686-linux]
"foo"



The patch (beware of too long lines):

[aleksi@dogma ruby-2001-08-12]$ diff -u orig/ruby/marshal.c marshal.c
--- orig/ruby/marshal.c	Tue Jul 31 11:33:17 2001
+++ marshal.c	Sun Aug 12 15:10:47 2001
@@ -1038,14 +1038,16 @@
     int argc;
     VALUE *argv;
 {
-    VALUE port, proc;
+    VALUE port, proc, override;
     int major, minor;
     VALUE v;
     OpenFile *fptr;
     struct load_arg arg;
     volatile VALUE hash;	/* protect from GC */
 
-    rb_scan_args(argc, argv, "11", &port, &proc);
+    if ( rb_scan_args(argc, argv, "12", &port, &proc, &override) < 3){
+      override = Qfalse;
+    }
     if (rb_obj_is_kind_of(port, rb_cIO)) {
 	rb_io_binmode(port);
 	GetOpenFile(port, fptr);
@@ -1066,15 +1068,17 @@
 
     major = r_byte(&arg);
     minor = r_byte(&arg);
-    if (major != MARSHAL_MAJOR || minor > MARSHAL_MINOR) {
+    if ( RTEST(override) ){
+      if (major != MARSHAL_MAJOR || minor > MARSHAL_MINOR) {
 	rb_raise(rb_eTypeError, "incompatible marshal file format (can't
be read)\n\
 \tformat version %d.%d required; %d.%d given",
 		 MARSHAL_MAJOR, MARSHAL_MINOR, major, minor);
-    }
-    if (RTEST(ruby_verbose) && minor != MARSHAL_MINOR) {
+      }
+      if (RTEST(ruby_verbose) && minor != MARSHAL_MINOR) {
 	rb_warn("incompatible marshal file format (can be read)\n\
 \tformat version %d.%d required; %d.%d given",
 		MARSHAL_MAJOR, MARSHAL_MINOR, major, minor);
+      }
     }
 
     arg.symbol = st_init_numtable();