sagemathgh-37951: declare the last arg to GAP_CallFunc3Args volatile

    
This appears to fix sagemath#37026 (segfaults in src/sage/libs/gap/element.pyx
with Python 3.12 and gcc 13.2.1)

See also
sagemath#36407 (comment)

The corresponding gcc 13.2.1's bug (or feature) is being dealt with
here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114872
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URL: sagemath#37951
Reported by: Dima Pasechnik
Reviewer(s): Dima Pasechnik, Gonzalo Tornaría

src/sage/libs/gap/element.pyx

@@ -2504,6 +2504,7 @@ cdef class GapElement_Function(GapElement):
         cdef Obj result = NULL
         cdef Obj arg_list
         cdef int n = len(args)
+        cdef volatile Obj v2
 
         if n > 0 and n <= 3:
             libgap = self.parent()
@@ -2522,10 +2523,11 @@ cdef class GapElement_Function(GapElement):
                                            (<GapElement>a[0]).value,
                                            (<GapElement>a[1]).value)
             elif n == 3:
+                v2 = (<GapElement>a[2]).value
                 result = GAP_CallFunc3Args(self.value,
                                            (<GapElement>a[0]).value,
                                            (<GapElement>a[1]).value,
-                                           (<GapElement>a[2]).value)
+                                           v2)
             else:
                 arg_list = make_gap_list(args)
                 result = GAP_CallFuncList(self.value, arg_list)