sync with w3m-0.2.2-inu-1.1/gc

gc/doc/README.environment

@@ -1,5 +1,5 @@
 The garbage collector looks at a number of environment variables which are
-the used to affect its operation.  These are examined only on Un*x-like
+then used to affect its operation.  These are examined only on Un*x-like
 platforms.
 
 GC_INITIAL_HEAP_SIZE=<bytes> -	Initial heap size in bytes.  May speed up
@@ -32,6 +32,27 @@ GC_NPROCS=<n> - Linux w/threads only.  Explicitly sets the number of processors
 GC_NO_BLACKLIST_WARNING - Prevents the collector from issuing
 		"Needed to allocate blacklisted block at ..." warnings.
 
+GC_IGNORE_GCJ_INFO - Ignore the type descriptors implicitly supplied by
+		     GC_gcj_malloc and friends.  This is useful for debugging
+		     descriptor generation problems, and possibly for
+		     temporarily working around such problems.  It forces a
+		     fully conservative scan of all heap objects except
+		     those known to be pointerfree, and may thus have other
+		     adverse effects.
+
+GC_PRINT_BACK_HEIGHT - Print max length of chain through unreachable objects
+		     ending in a reachable one.  If this number remains
+		     bounded, then the program is "GC robust".  This ensures
+		     that a fixed number of misidentified pointers can only
+		     result in a bounded space leak.  This currently only
+		     works if debugging allocation is used throughout.
+		     It increases GC space and time requirements appreciably.
+		     This feature is still somewhat experimental, and requires
+		     that the collector have been built with MAKE_BACK_GRAPH
+		     defined.  For details, see Boehm, "Bounding Space Usage
+		     of Conservative Garbage Collectors", POPL 2001, or
+		     http://lib.hpl.hp.com/techpubs/2001/HPL-2001-251.html .
+
 The following turn on runtime flags that are also program settable.  Checked
 only during initialization.  We expect that they will usually be set through
 other means, but this may help with debugging and testing: