From afcb6d0bc7abcdbca6b18d020deeff24d1ad197f Mon Sep 17 00:00:00 2001 From: Alan Mackenzie Date: Mon, 4 Sep 2023 12:51:24 +0000 Subject: [PATCH] Correct the handling of symbols with position in equal * src/fns.c (internal_equal): Only regard symbols with position as their symbols when symbols-with-pos-enabled is non-nil. * doc/lispref/symbols.texi (Symbols with Position): Expand the description of symbols with position, in particular the way they work with eq and equal. * doc/lispref/objects.texi (Equality Predicates): Describe how eq and equal handle symbols with position. * test/src/fns-tests.el (fns-tests-equal-symbols-with-position): New tests for symbols with position. --- doc/lispref/objects.texi | 11 +++++++++++ doc/lispref/symbols.texi | 40 +++++++++++++++++++++++++++------------- src/fns.c | 20 ++++++++++++++------ test/src/fns-tests.el | 20 ++++++++++++++++++++ 4 files changed, 72 insertions(+), 19 deletions(-) diff --git a/doc/lispref/objects.texi b/doc/lispref/objects.texi index ad079e0d63a..784d59720ed 100644 --- a/doc/lispref/objects.texi +++ b/doc/lispref/objects.texi @@ -2206,6 +2206,10 @@ and the same non-fixnum numeric type, then they might or might not be the same object, and @code{eq} returns @code{t} or @code{nil} depending on whether the Lisp interpreter created one object or two. +If @var{object1} or @var{object2} is a symbol with position, @code{eq} +regards it as its bare symbol when @code{symbols-with-pos-enabled} is +non-@code{nil} (@pxref{Symbols with Position}). + @example @group (eq 'foo 'foo) @@ -2363,6 +2367,13 @@ same sequence of character codes and all these codes are in the range 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 +@code{symbols-with-pos-enabled} is non-@code{nil}. Otherwise +@code{equal} compares two symbols with position by recursively +comparing their components. @xref{Symbols with Position}. + Other objects are considered @code{equal} only if they are @code{eq}. For example, two distinct buffers are never considered @code{equal}, even if their textual contents are the same. diff --git a/doc/lispref/symbols.texi b/doc/lispref/symbols.texi index 34db0caf3a8..1f3b677d7fb 100644 --- a/doc/lispref/symbols.texi +++ b/doc/lispref/symbols.texi @@ -783,10 +783,15 @@ Symbol forms whose names start with @samp{#_} are not transformed. @cindex bare symbol A @dfn{symbol with position} is a symbol, the @dfn{bare symbol}, -together with an unsigned integer called the @dfn{position}. These -objects are intended for use by the byte compiler, which records in -them the position of each symbol occurrence and uses those positions -in warning and error messages. +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}). + +Symbols with position are for the use of the byte compiler, which +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}. The printed representation of a symbol with position uses the hash notation outlined in @ref{Printed Representation}. It looks like @@ -798,11 +803,20 @@ 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 bare symbols do. For example, @samp{(eq -# foo)} has a value @code{t} when that variable -is set (but @code{nil} when it isn't set). Most of the time in Emacs this -variable is @code{nil}, but the byte compiler binds it to @code{t} -when it runs. +positions behave just as their bare symbols would. For example, +@samp{(eq # 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 @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. + +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. Typically, symbols with position are created by the byte compiler calling the reader function @code{read-positioning-symbols} @@ -810,17 +824,17 @@ calling the reader function @code{read-positioning-symbols} @code{position-symbol}. @defvar symbols-with-pos-enabled -When this variable is non-@code{nil}, symbols with position behave +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. @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. +When bound to non-@code{nil}, the Lisp printer prints only the bare +symbol of a symbol with position, ignoring the position. @end defvar -@defun symbol-with-pos-p symbol. +@defun symbol-with-pos-p symbol This function returns @code{t} if @var{symbol} is a symbol with position, @code{nil} otherwise. @end defun diff --git a/src/fns.c b/src/fns.c index ae9969a5432..bd1d63a58c4 100644 --- a/src/fns.c +++ b/src/fns.c @@ -2774,10 +2774,13 @@ internal_equal (Lisp_Object o1, Lisp_Object o2, enum equal_kind equal_kind, /* A symbol with position compares the contained symbol, and is `equal' to the corresponding ordinary symbol. */ - if (SYMBOL_WITH_POS_P (o1)) - o1 = SYMBOL_WITH_POS_SYM (o1); - if (SYMBOL_WITH_POS_P (o2)) - o2 = SYMBOL_WITH_POS_SYM (o2); + if (symbols_with_pos_enabled) + { + if (SYMBOL_WITH_POS_P (o1)) + o1 = SYMBOL_WITH_POS_SYM (o1); + if (SYMBOL_WITH_POS_P (o2)) + o2 = SYMBOL_WITH_POS_SYM (o2); + } if (BASE_EQ (o1, o2)) return true; @@ -2825,8 +2828,8 @@ internal_equal (Lisp_Object o1, Lisp_Object o2, enum equal_kind equal_kind, if (ASIZE (o2) != size) return false; - /* Compare bignums, overlays, markers, and boolvectors - specially, by comparing their values. */ + /* Compare bignums, overlays, markers, boolvectors, and + symbols with position specially, by comparing their values. */ if (BIGNUMP (o1)) return mpz_cmp (*xbignum_val (o1), *xbignum_val (o2)) == 0; if (OVERLAYP (o1)) @@ -2858,6 +2861,11 @@ internal_equal (Lisp_Object o1, Lisp_Object o2, enum equal_kind equal_kind, if (TS_NODEP (o1)) return treesit_node_eq (o1, o2); #endif + if (SYMBOL_WITH_POS_P(o1)) /* symbols_with_pos_enabled is false. */ + return (BASE_EQ (XSYMBOL_WITH_POS (o1)->sym, + XSYMBOL_WITH_POS (o2)->sym) + && BASE_EQ (XSYMBOL_WITH_POS (o1)->pos, + XSYMBOL_WITH_POS (o2)->pos)); /* Aside from them, only true vectors, char-tables, compiled functions, and fonts (font-spec, font-entity, font-object) diff --git a/test/src/fns-tests.el b/test/src/fns-tests.el index 79ae4393f40..9c09e4f0c33 100644 --- a/test/src/fns-tests.el +++ b/test/src/fns-tests.el @@ -98,6 +98,26 @@ (should-not (equal-including-properties #("a" 0 1 (k "v")) #("b" 0 1 (k "v"))))) +(ert-deftest fns-tests-equal-symbols-with-position () + "Test `eq' and `equal' on symbols with position." + (let ((foo1 (position-symbol 'foo 42)) + (foo2 (position-symbol 'foo 666)) + (foo3 (position-symbol 'foo 42))) + (let (symbols-with-pos-enabled) + (should (eq foo1 foo1)) + (should (equal foo1 foo1)) + (should-not (eq foo1 foo2)) + (should-not (equal foo1 foo2)) + (should-not (eq foo1 foo3)) + (should (equal foo1 foo3))) + (let ((symbols-with-pos-enabled t)) + (should (eq foo1 foo1)) + (should (equal foo1 foo1)) + (should (eq foo1 foo2)) + (should (equal foo1 foo2)) + (should (eq foo1 foo3)) + (should (equal foo1 foo3))))) + (ert-deftest fns-tests-reverse () (should-error (reverse)) (should-error (reverse 1)) -- 2.39.2