From c5461d03a411ff5c6f43885a0a9030e8a94bbc2e Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 14 Jun 2016 12:19:36 -0700
Subject: [PATCH] Port to platforms where char * has top bit set
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This fixes a five-year-old FIXME comment.  Although I don’t know
of a platform where this is a problem in practice, better safe
than sorry.
* src/doc.c (Fdocumentation): If SUBRP, simply use doc as integer,
as it is now an integer, not char *.
(store_function_docstring): Offset is now EMACS_INT, not ptrdiff_t;
this is a file offset and EMACS_INT is better if --with-wide-int.
If SUBRP, simply store the offset rather than negating it and
converting it to char *.
* src/lisp.h (struct Lisp_Subr.doc): Now EMACS_INT, not char *.
---
 src/doc.c  | 18 +++---------------
 src/lisp.h |  2 +-
 2 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/src/doc.c b/src/doc.c
index 7107580cf8..6ffdad10f0 100644
--- a/src/doc.c
+++ b/src/doc.c
@@ -339,16 +339,7 @@ string is passed through `substitute-command-keys'.  */)
   if (CONSP (fun) && EQ (XCAR (fun), Qmacro))
     fun = XCDR (fun);
   if (SUBRP (fun))
-    {
-      if (XSUBR (fun)->doc == 0)
-	return Qnil;
-      /* FIXME: This is not portable, as it assumes that string
-	 pointers have the top bit clear.  */
-      else if ((intptr_t) XSUBR (fun)->doc >= 0)
-	doc = build_string (XSUBR (fun)->doc);
-      else
-	doc = make_number ((intptr_t) XSUBR (fun)->doc);
-    }
+    doc = make_number (XSUBR (fun)->doc);
   else if (COMPILEDP (fun))
     {
       if ((ASIZE (fun) & PSEUDOVECTOR_SIZE_MASK) <= COMPILED_DOC_STRING)
@@ -473,7 +464,7 @@ aren't strings.  */)
 /* Scanning the DOC files and placing docstring offsets into functions.  */
 
 static void
-store_function_docstring (Lisp_Object obj, ptrdiff_t offset)
+store_function_docstring (Lisp_Object obj, EMACS_INT offset)
 {
   /* Don't use indirect_function here, or defaliases will apply their
      docstrings to the base functions (Bug#2603).  */
@@ -502,10 +493,7 @@ store_function_docstring (Lisp_Object obj, ptrdiff_t offset)
 
   /* Lisp_Subrs have a slot for it.  */
   else if (SUBRP (fun))
-    {
-      intptr_t negative_offset = - offset;
-      XSUBR (fun)->doc = (char *) negative_offset;
-    }
+    XSUBR (fun)->doc = offset;
 
   /* Bytecode objects sometimes have slots for it.  */
   else if (COMPILEDP (fun))
diff --git a/src/lisp.h b/src/lisp.h
index 972ca33511..e0eb52a84e 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -1752,7 +1752,7 @@ struct Lisp_Subr
     short min_args, max_args;
     const char *symbol_name;
     const char *intspec;
-    const char *doc;
+    EMACS_INT doc;
   };
 
 enum char_table_specials
-- 
2.39.2