Rakudo and Fakecutable Memory Requirements

[chromatic]

I've been reviewing memory leaks and memory usage in Rakudo.  A series of big 
(bigger than 1Mb) allocations occurs as part of loading Rakudo from the perl6 
fakecutable.  As far as I can tell, it's completely unnecessary: it's 
PackFile_new() reading the contents of the contained packfile into memory.

As the fakecutable already contains this packfile in a native form as part of 
the executable, there's no need to copy this memory, and we can save Rakudo a 
few MB.

The inline patch (not for application) does so, but it causes segfaults during 
global destruction as free()ing this memory is inappropriate.  Admittedly 
hijacking the is_mmap_ped flag on the PackFile is the wrong approach, but when 
I skip global destruction, I can see memory savings.

Someone who knows (or wants to know) the packfile code better than I do might 
be able to figure out a better approach.

-- c

diff --git a/tools/dev/pbc_to_exe.pir b/tools/dev/pbc_to_exe.pir
index 804ea65..f37952b 100644
--- a/tools/dev/pbc_to_exe.pir
+++ b/tools/dev/pbc_to_exe.pir
@@ -95,7 +95,7 @@ HEADER
             Parrot_set_run_core(interp, (Parrot_Run_core_t)RUNCORE);
             Parrot_set_flag(interp, PARROT_DESTROY_FLAG);
 
-            pf = PackFile_new(interp, 0);
+            pf = PackFile_new(interp, 1);
             if (!pf)
                 return 1;