🚀 go-pugleaf

Emacs version:	19.27
Machine:	SparcStation2
OS:		SunOS 4.1.3
Configuration:	compiled with REL_ALLOC and HAVE_X11 set

  I think I found a bug which can cause text loss. The bug is in emacs
which is compiled with REL_ALLOC set, but it depends on timing and
seldom appears.

  The following is the questionable part, which is in make_gap(), line
272 of src/insdel.c.


  BLOCK_INPUT;
  result = BUFFER_REALLOC (BEG_ADDR, (Z - BEG + GAP_SIZE + increment));
  UNBLOCK_INPUT;

  if (result == 0)
    memory_full ();
  BEG_ADDR = result;


  The code saves the return value of BUFFER_REALLOC() (macro of
r_re_alloc()) to `result', next UNBLOCK_INPUT, then sets the value in
`result' to `BEG_ADDR'. I think this is wrong. Once you call
UNBLOCK_INPUT, interrupt handler can call malloc(), and malloc() can
call (*__morecore)() (pointer to r_alloc_sbrk()) which relocates
blocks. If the block relocation occurs just after UNBLOCK_INPUT, the
value in `result' is probably wrong! I think `BEG_ADDR = result' must
be done before UNBLOCK_INPUT.

-- 
Kanazawa Yuzi
kanazawa@flab.fujitsu.co.jp