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Change bare-symbol back to match intent

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Also, attempt to document the intent better.
Problem reported by Alan Mackenzie (Bug#69684).
* src/data.c (Fbare_symbol): Do not signal if the SYM is a symbol
with position and symbols-with-pos-enabled is nil.  Instead,
ignore symbols-with-pos-enabled, as that was the intent.
* test/src/data-tests.el (data-tests-bare-symbol):
New test, to help prevent this bug from reoccurring.
This commit is contained in:
Paul Eggert 2024-03-11 00:03:39 -07:00
parent bbc53e0bcf
commit 2d61ebb505
4 changed files with 72 additions and 50 deletions
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6
doc/lispref/objects.texi
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@ -2399,10 +2399,10 @@ The @code{equal} function recursively compares the contents of objects
if they are integers, strings, markers, vectors, bool-vectors,
byte-code function objects, char-tables, records, or font objects.
If @var{object1} or @var{object2} is a symbol with position,
@code{equal} regards it as its bare symbol when
If @var{object1} or @var{object2} contains symbols with position,
@code{equal} treats them as if they were their bare symbols when
@code{symbols-with-pos-enabled} is non-@code{nil}. Otherwise
@code{equal} compares two symbols with position by recursively
@code{equal} compares two symbols with position by
comparing their components. @xref{Symbols with Position}.
Other objects are considered @code{equal} only if they are @code{eq}.

76
doc/lispref/symbols.texi
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@ -780,13 +780,16 @@ Symbol forms whose names start with @samp{#_} are not transformed.
@cindex symbol with position
@cindex bare symbol
A @dfn{symbol with position} is a symbol, the @dfn{bare symbol},
together with an unsigned integer called the @dfn{position}. Symbols
with position don't themselves have entries in the obarray (though
their bare symbols do; @pxref{Creating Symbols}).
A @dfn{symbol with position} is a symbol, called the @dfn{bare symbol},
together with a nonnegative fixnum called the @dfn{position}.
Even though a symbol with position often acts like its bare symbol,
it is not a symbol: instead, it is an object that has both a bare symbol
and a position. Because symbols with position are not symbols,
they don't have entries in the obarray, though their bare symbols
typically do (@pxref{Creating Symbols}).
Symbols with position are for the use of the byte compiler, which
records in them the position of each symbol occurrence and uses those
The byte compiler uses symbols with position,
records in them the position of each symbol occurrence, and uses those
positions in warning and error messages. They shouldn't normally be
used otherwise. Doing so can cause unexpected results with basic
Emacs functions such as @code{eq} and @code{equal}.
@ -799,22 +802,19 @@ just the bare symbol to be printed by binding the variable
operation. The byte compiler does this before writing its output to
the compiled Lisp file.
For most purposes, when the flag variable
@code{symbols-with-pos-enabled} is non-@code{nil}, symbols with
positions behave just as their bare symbols would. For example,
@samp{(eq #<symbol foo at 12345> foo)} has a value @code{t} when the
variable is set; likewise, @code{equal} will treat a symbol with
position argument as its bare symbol.
When the flag variable @code{symbols-with-pos-enabled} is non-@code{nil},
a symbol with position ordinarily behaves like its bare symbol.
For example, @samp{(eq (position-symbol 'foo 12345) 'foo)} yields @code{t},
and @code{equal} likewise treats a symbol with position as its bare symbol.
When @code{symbols-with-pos-enabled} is @code{nil}, any symbols with
position continue to exist, but do not behave as symbols, or have the
other useful properties outlined in the previous paragraph. @code{eq}
returns @code{t} when given identical arguments, and @code{equal}
returns @code{t} when given arguments with @code{equal} components.
When @code{symbols-with-pos-enabled} is @code{nil}, symbols with
position behave as themselves, not as symbols. For example, @samp{(eq
(position-symbol 'foo 12345) 'foo)} yields @code{nil}, and @code{equal}
likewise treats a symbol with position as not equal to its bare symbol.
Most of the time in Emacs @code{symbols-with-pos-enabled} is
@code{nil}, but the byte compiler and the native compiler bind it to
@code{t} when they run.
@code{t} when they run and Emacs runs a little more slowly in this case.
Typically, symbols with position are created by the byte compiler
calling the reader function @code{read-positioning-symbols}
@ -822,36 +822,44 @@ calling the reader function @code{read-positioning-symbols}
@code{position-symbol}.
@defvar symbols-with-pos-enabled
When this variable is non-@code{nil}, a symbol with position behaves
like the contained bare symbol. Emacs runs a little more slowly in
this case.
This variable affects the behavior of symbols with position when they
are not being printed and are not arguments to one of the functions
defined later in this section. When this variable is non-@code{nil},
such a symbol with position behaves like its bare symbol; otherwise it
behaves as itself, not as a symbol.
@end defvar
@defvar print-symbols-bare
When bound to non-@code{nil}, the Lisp printer prints only the bare
symbol of a symbol with position, ignoring the position.
Otherwise a symbol with position prints as itself, not as a symbol.
@end defvar
@defun symbol-with-pos-p symbol
This function returns @code{t} if @var{symbol} is a symbol with
@defun symbol-with-pos-p object
This function returns @code{t} if @var{object} is a symbol with
position, @code{nil} otherwise.
Unlike @code{symbolp}, this function ignores @code{symbols-with-pos-enabled}.
@end defun
@defun bare-symbol symbol
This function returns the bare symbol contained in @var{symbol}, or
@var{symbol} itself if it is already a bare symbol. For any other
type of object, it signals an error.
@defun bare-symbol sym
This function returns the bare symbol of the symbol with
position @var{sym}, or @var{sym} itself if it is already a symbol.
For any other type of object, it signals an error.
This function ignores @code{symbols-with-pos-enabled}.
@end defun
@defun symbol-with-pos-pos symbol
This function returns the position, a number, from a symbol with
position. For any other type of object, it signals an error.
@defun symbol-with-pos-pos sympos
This function returns the position, a nonnegative fixnum, from the symbol with
position @var{sympos}. For any other type of object, it signals an error.
This function ignores @code{symbols-with-pos-enabled}.
@end defun
@defun position-symbol sym pos
Make a new symbol with position. @var{sym} is either a bare symbol or
a symbol with position, and supplies the symbol part of the new
object. @var{pos} is either an integer which becomes the number part
of the new object, or a symbol with position whose position is used.
Make a new symbol with position. The new object's bare symbol is taken
from @var{sym}, which is either a symbol, or a symbol with position
whose bare symbol is used. The new object's position is taken from
@var{pos}, which is either a nonnegative fixnum, or a symbol with
position whose position is used.
Emacs signals an error if either argument is invalid.
This function ignores @code{symbols-with-pos-enabled}.
@end defun

35
src/data.c
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@ -339,7 +339,8 @@ DEFUN ("bare-symbol-p", Fbare_symbol_p, Sbare_symbol_p, 1, 1, 0,
}
DEFUN ("symbol-with-pos-p", Fsymbol_with_pos_p, Ssymbol_with_pos_p, 1, 1, 0,
doc: /* Return t if OBJECT is a symbol together with position. */
doc: /* Return t if OBJECT is a symbol together with position.
Ignore `symbols-with-pos-enabled'. */
attributes: const)
(Lisp_Object object)
{
@ -789,25 +790,32 @@ Doing that might make Emacs dysfunctional, and might even crash Emacs. */)
}
DEFUN ("bare-symbol", Fbare_symbol, Sbare_symbol, 1, 1, 0,
doc: /* Extract, if need be, the bare symbol from SYM, a symbol. */)
doc: /* Extract, if need be, the bare symbol from SYM.
SYM is either a symbol or a symbol with position.
Ignore `symbols-with-pos-enabled'. */)
(register Lisp_Object sym)
{
CHECK_SYMBOL (sym);
return BARE_SYMBOL_P (sym) ? sym : XSYMBOL_WITH_POS_SYM (sym);
if (BARE_SYMBOL_P (sym))
return sym;
if (SYMBOL_WITH_POS_P (sym))
return XSYMBOL_WITH_POS_SYM (sym);
xsignal2 (Qwrong_type_argument, list2 (Qsymbolp, Qsymbol_with_pos_p), sym);
}
DEFUN ("symbol-with-pos-pos", Fsymbol_with_pos_pos, Ssymbol_with_pos_pos, 1, 1, 0,
doc: /* Extract the position from a symbol with position. */)
(register Lisp_Object ls)
doc: /* Extract the position from the symbol with position SYMPOS.
Ignore `symbols-with-pos-enabled'. */)
(register Lisp_Object sympos)
{
CHECK_TYPE (SYMBOL_WITH_POS_P (ls), Qsymbol_with_pos_p, ls);
return XSYMBOL_WITH_POS_POS (ls);
CHECK_TYPE (SYMBOL_WITH_POS_P (sympos), Qsymbol_with_pos_p, sympos);
return XSYMBOL_WITH_POS_POS (sympos);
}
DEFUN ("remove-pos-from-symbol", Fremove_pos_from_symbol,
Sremove_pos_from_symbol, 1, 1, 0,
doc: /* If ARG is a symbol with position, return it without the position.
Otherwise, return ARG unchanged. Compare with `bare-symbol'. */)
Otherwise, return ARG unchanged. Ignore `symbols-with-pos-enabled'.
Compare with `bare-symbol'. */)
(register Lisp_Object arg)
{
if (SYMBOL_WITH_POS_P (arg))
@ -816,10 +824,11 @@ Otherwise, return ARG unchanged. Compare with `bare-symbol'. */)
}
DEFUN ("position-symbol", Fposition_symbol, Sposition_symbol, 2, 2, 0,
doc: /* Create a new symbol with position.
doc: /* Make a new symbol with position.
SYM is a symbol, with or without position, the symbol to position.
POS, the position, is either a fixnum or a symbol with position from which
the position will be taken. */)
POS, the position, is either a nonnegative fixnum,
or a symbol with position from which the position will be taken.
Ignore `symbols-with-pos-enabled'. */)
(register Lisp_Object sym, register Lisp_Object pos)
{
Lisp_Object bare = Fbare_symbol (sym);
@ -4374,7 +4383,7 @@ This variable cannot be set; trying to do so will signal an error. */);
DEFSYM (Qsymbols_with_pos_enabled, "symbols-with-pos-enabled");
DEFVAR_BOOL ("symbols-with-pos-enabled", symbols_with_pos_enabled,
doc: /* Non-nil when "symbols with position" can be used as symbols.
doc: /* If non-nil, a symbol with position ordinarily behaves as its bare symbol.
Bind this to non-nil in applications such as the byte compiler. */);
symbols_with_pos_enabled = false;

5
test/src/data-tests.el
View File

@ -833,4 +833,9 @@ comparing the subr with a much slower Lisp implementation."
(should-error (defalias 'data-tests--da-c 'data-tests--da-d)
:type 'cyclic-function-indirection))
(ert-deftest data-tests-bare-symbol ()
(dolist (symbols-with-pos-enabled '(nil t))
(dolist (sym (list nil t 'xyzzy (make-symbol "")))
(should (eq sym (bare-symbol (position-symbol sym 0)))))))
;;; data-tests.el ends here