bug#4585: A flaky temacs dump failure

[Sergio Pokrovskij]

There is a very infrequent failure at the temacs dump stage, which
seems to be due to a read from uninitialized memory.

The problem is common to several versions of emacs; in this report I
use v. 22.3; it is all the same in the cvs version.

Sometimes it leads to a Segmentation Fault.  This is a flaky
(unstable) behavior, but there are two ways to reproduce the symptom:

1. Compile with Intel's icc compiler using the -check-uninit option, or

2. Use valgrind (for either gcc or icc build -- the results are
   similar).

src/temacs produced by Intel's icc reports this:
,----
| LC_ALL=C ./temacs -batch -l loadup dump
|
| Run-Time Check Failure: The variable '__d1' is being used without
being initialized
|
| make[1]: *** [emacs] Aborted
`----

But I suppose you should prefer the GNU utilities.

Here is the Valgrind's output for the gcc build (it has completed
successfully and I am using the constructed src/emacs to prepare this
report and give the build details; but after the build I am repeating
the temacs dump with Valgrind):

% LC_ALL=C valgrind --quiet --trace-children=yes --tool=memcheck
./temacs -batch -l loadup dump
==29515== Invalid read of size 4
==29515==    at 0x80BA240: reset_buffer_local_variables (buffer.c:748)
==29515==    by 0x80C00FA: Fget_buffer_create (buffer.c:413)
==29515==    by 0x805F239: ensure_echo_area_buffers (xdisp.c:7956)
==29515==    by 0x805F2D2: with_echo_area_buffer (xdisp.c:7992)
==29515==    by 0x805F6AB: current_message (xdisp.c:8484)
==29515==    by 0x805F6DB: push_message (xdisp.c:8519)
==29515==    by 0x80F2FD5: Fgarbage_collect (alloc.c:5123)
==29515==    by 0x810769D: Ffuncall (eval.c:2927)
==29515==    by 0x8107B88: call2 (eval.c:2800)
==29515==    by 0x8107C47: Fsignal (eval.c:1652)
==29515==    by 0x8107E27: xsignal (eval.c:1725)
==29515==    by 0x810830F: xsignal1 (eval.c:1742)
==29515==  Address 0x618 is not stack'd, malloc'd or (recently) free'd
==29515==
==29515== Process terminating with default action of signal 11 (SIGSEGV)
==29515==  Access not within mapped region at address 0x618
==29515==    at 0x80BA240: reset_buffer_local_variables (buffer.c:748)
==29515==    by 0x80C00FA: Fget_buffer_create (buffer.c:413)
==29515==    by 0x805F239: ensure_echo_area_buffers (xdisp.c:7956)
==29515==    by 0x805F2D2: with_echo_area_buffer (xdisp.c:7992)
==29515==    by 0x805F6AB: current_message (xdisp.c:8484)
==29515==    by 0x805F6DB: push_message (xdisp.c:8519)
==29515==    by 0x80F2FD5: Fgarbage_collect (alloc.c:5123)
==29515==    by 0x810769D: Ffuncall (eval.c:2927)
==29515==    by 0x8107B88: call2 (eval.c:2800)
==29515==    by 0x8107C47: Fsignal (eval.c:1652)
==29515==    by 0x8107E27: xsignal (eval.c:1725)
==29515==    by 0x810830F: xsignal1 (eval.c:1742)
Segmentation fault
%
=============================================

In GNU Emacs 22.3.1 (i686-pc-linux-gnu)
 of 2009-09-29 on nsticlxlqa1
configured using `configure  '--without-x''

Important settings:
  value of $LC_ALL: en_US.iso885915
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  locale-coding-system: iso-8859-15
  default-enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  encoded-kbd-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  line-number-mode: t

Recent input:
ESC x r e p o r t - e m a c s - b u g RET

Recent messages:
("./emacs" "-q")
Loading encoded-kb...done
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading emacsbug...
Loading regexp-opt...done
Loading emacsbug...done


-- 
Sergio