Undocumented %-constructs (was: memory consumption with pure-space-overflow)

[Juri Linkov <juri@jurta.org>]

>     Below is a list of options currently documented in Info and docstring,
>     and really implemented options (thus spaces denote undocumented options):
>
>     In the node (info "(elisp)%-Constructs"): bc fFiIlmMnpPst  *+&[]-%
>     In the docstring of `mode-line-format':   bc fFiIlm npPs zZ*+&[]-%
>     Really implemented in `decode_mode_spec': bcefFiIlm npPstzZ*+&[]-%
>
> Would someone please write the missing documentation for options
> e, t, z, Z, then ack?

Below is a patch with the missing documentation based on the source code.
Please correct me if I misinterpreted the meaning of these constructs.
I removed %M from Info because it is not supported, while %m is supported,
albeit obsolete.

Index: lispref/modes.texi
===================================================================
RCS file: /sources/emacs/emacs/lispref/modes.texi,v
retrieving revision 1.139
diff -c -r1.139 modes.texi
*** lispref/modes.texi	30 Apr 2006 02:35:35 -0000	1.139
--- lispref/modes.texi	11 May 2006 23:03:59 -0000
***************
*** 1927,1932 ****
--- 1931,1939 ----
  @item %c
  The current column number of point.
  
+ @item %e
+ The error message if Emacs is close to out of memory for Lisp objects.
+ 
  @item %f
  The visited file name, obtained with the @code{buffer-file-name}
  function.  @xref{Buffer File Name}.
***************
*** 1972,1977 ****
--- 1979,1990 ----
  meaningful distinction only on certain operating systems (@pxref{MS-DOS
  File Types}).
  
+ @item %z
+ The mnemonics of buffer, terminal, and keyboard coding systems.
+ 
+ @item %Z
+ Like @samp{%z}, but including the end-of-line format.
+ 
  @item %*
  @samp{%} if the buffer is read only (see @code{buffer-read-only}); @*
  @samp{*} if the buffer is modified (see @code{buffer-modified-p}); @*
***************
*** 2003,2018 ****
  string in which @code{%}-constructs are allowed.
  @end table
  
! The following two @code{%}-constructs are still supported, but they are
! obsolete, since you can get the same results with the variables
! @code{mode-name} and @code{global-mode-string}.
  
  @table @code
  @item %m
  The value of @code{mode-name}.
- 
- @item %M
- The value of @code{global-mode-string}.
  @end table
  
  @node Properties in Mode
--- 2016,2028 ----
  string in which @code{%}-constructs are allowed.
  @end table
  
! The following @code{%}-construct is still supported, but it is
! obsolete, since you can get the same result with the variable
! @code{mode-name}.
  
  @table @code
  @item %m
  The value of @code{mode-name}.
  @end table
  
  @node Properties in Mode

Index: src/buffer.c
===================================================================
RCS file: /sources/emacs/emacs/src/buffer.c,v
retrieving revision 1.501
diff -c -r1.501 buffer.c
*** src/buffer.c	25 Feb 2006 23:33:57 -0000	1.501
--- src/buffer.c	11 May 2006 23:06:16 -0000
***************
*** 5440,5447 ****
--- 5440,5449 ----
          or print Bottom or All.
    %m -- print the mode name.
    %n -- print Narrow if appropriate.
+   %t -- visited file is text or binary (if OS supports this distinction).
    %z -- print mnemonics of buffer, terminal, and keyboard coding systems.
    %Z -- like %z, but including the end-of-line format.
+   %e -- print error message about full memory.
    %[ -- print one [ for each recursive editing level.  %] similar.
    %% -- print %.   %- -- print infinitely many dashes.
  Decimal digits after the % specify field width to which to pad.  */);

-- 
Juri Linkov
http://www.jurta.org/emacs/