~ chicken-core (chicken-5) 9d36c362e18afd2b136f276cb7d2070d838848b6

commit 9d36c362e18afd2b136f276cb7d2070d838848b6
Author:     Peter Bex <peter@more-magic.net>
AuthorDate: Sat Oct 17 13:19:36 2015 +0200
Commit:     Evan Hanson <evhan@foldling.org>
CommitDate: Mon Oct 26 08:58:13 2015 +1300

    Try to detect corrupted data before performing GC_REALLOC.
    
    If an "impossible" object in the stack or heap: one that has a size
    that's larger than the memory area that contains it, we know we have a
    data corruption on our hands.  Panic immediately instead of going in
    for the reallocating GC.  This prevents the memory state from being
    mutated any more, which may help in debugging.
    
    Signed-off-by: Evan Hanson <evhan@foldling.org>

diff --git a/runtime.c b/runtime.c
index a4d346f3..43edfe97 100644
--- a/runtime.c
+++ b/runtime.c
@@ -3214,6 +3214,11 @@ C_regparm void C_fcall really_mark(C_word *x)
     bytes = (h & C_BYTEBLOCK_BIT) ? n : n * sizeof(C_word);
 
     if(((C_byte *)p2 + bytes + sizeof(C_word)) > tospace_limit) {
+      /* Detect impossibilities before GC_REALLOC to preserve state: */
+      if (C_in_stackp((C_word)p) && bytes > stack_size)
+        panic(C_text("Detected corrupted data in stack"));
+      if (C_in_heapp((C_word)p) && bytes > (heap_size / 2))
+        panic(C_text("Detected corrupted data in heap"));
       if(C_heap_size_is_fixed)
 	panic(C_text("out of memory - heap full"));