Fix mis-declarations of non-const functions

Problem for mpz_get_d_rounded reported by Helmut Eller in:
https://lists.gnu.org/r/emacs-devel/2025-11/msg00795.html
* lib-src/make-docfile.c (DEFUN_pure): New constant.
(write_globals, scan_c_stream): Support "attributes: pure".
* src/bignum.h (mpz_get_d_rounded):
* src/data.c (Fsymbolp, Fmodule_function_p, Fintegerp, Fnumberp):
* src/lisp.h (bignum_to_double, bignum_to_intmax)
(bignum_to_uintmax, bignum_bufsize):
Now pure, not const, since they depend on current state.
For example, Fsymbolp now inspects symbols_with_pos_enabled,
and the bignum functions inspect bignum contents in memory.
* src/data.c (Feq):
* src/xfaces.c (Fface_attribute_relative_p):
No longer const, since they might abort when debugging.
* src/pdumper.h (pdumper_object_p, pdumper_cold_object_p)
(pdumper_find_object_type, pdumper_object_p_precise):
These are not const functions.  But there is no need to declare
them to be pure, either, as they’re inline so the compiler can
figure it out.

1 files changed, 12 insertions, 2 deletions

diff --git a/lib-src/make-docfile.c b/lib-src/make-docfile.c
index 6243f666955..d0ea463f299 100644
--- a/lib-src/make-docfile.c
+++ b/lib-src/make-docfile.c
@@ -577,7 +577,13 @@ struct global
 };
 
 /* Bit values for FLAGS field from the above.  Applied for DEFUNs only.  */
-enum { DEFUN_noreturn = 1, DEFUN_const = 2, DEFUN_noinline = 4 };
+enum
+  {
+    DEFUN_noreturn = 1,
+    DEFUN_const = 2,
+    DEFUN_noinline = 4,
+    DEFUN_pure = 8,
+  };
 
 /* All the variable names we saw while scanning C sources in `-g'
    mode.  */
@@ -752,6 +758,8 @@ write_globals (void)
             fputs (" ATTRIBUTE_COLD", stdout);
           if (globals[i].flags & DEFUN_const)
             fputs (" ATTRIBUTE_CONST", stdout);
+          if (globals[i].flags & DEFUN_pure)
+            fputs (" ATTRIBUTE_PURE", stdout);
 
           puts (";");
         }
@@ -1062,7 +1070,7 @@ scan_c_stream (FILE *infile)
                    attributes: attribute1 attribute2 ...)
                (Lisp_Object arg...)
 
-             Now only `const', `noinline' and `noreturn' attributes
+             Now only 'const', 'noinline', 'noreturn', and 'pure' attributes
              are used.  */
 
           /* Advance to the end of docstring.  */
@@ -1110,6 +1118,8 @@ scan_c_stream (FILE *infile)
                 g->flags |= DEFUN_noreturn;
               if (strstr (input_buffer, "const"))
                 g->flags |= DEFUN_const;
+              if (strstr (input_buffer, "pure"))
+                g->flags |= DEFUN_pure;
 
               /* Although the noinline attribute is no longer used,
                  leave its support in, in case it's needed later.  */