Fix JuliaLang#17219: conditionally lower ccall first arg

Without this compile step, ccall uses the first slotted version of the variable
regardless of whether it has been reassigned in the function body.

Fixes JuliaLang#17219
Fixes JuliaInterop/JavaCall.jl#37

See https://groups.google.com/forum/#!msg/julia-users/DyTQmsQaQl4/KmxQHSqACQAJ

src/julia-syntax.scm

@@ -3018,8 +3018,12 @@ f(x) = yt(x)
  ((call new)
  (let* ((ccall? (and (eq? (car e) 'call) (equal? (cadr e) '(core ccall))))
  (args (if ccall?
- ;; NOTE: first 3 arguments of ccall must be left in place
- (append (list-head (cdr e) 4)
+ ;; NOTE: 2nd and 3rd arguments of ccall must be left in place
+ ;; the 1st should be compiled if an atom.
+ (append (list (cadr e))
+ (cond (atom? (caddr e) (compile-args (list (caddr e)) break-labels))
+ (else (caddr e)))
+ (list-head (cdddr e) 2)
  (compile-args (list-tail e 5) break-labels))
  (compile-args (cdr e) break-labels)))
  (callex (cons (car e) args)))

test/ccall.jl

@@ -570,6 +570,13 @@ foo13031(x,y,z) = z
 foo13031p = cfunction(foo13031, Cint, (Ref{Tuple{}},Ref{Tuple{}},Cint))
 ccall(foo13031p, Cint, (Ref{Tuple{}},Ref{Tuple{}},Cint), (), (), 8)
 
+# issue 17219
+function ccall_reassigned_ptr(ptr::Ptr{Void})
+ ptr = Libdl.dlsym(Libdl.dlopen(libccalltest), "test_echo_p")
+ ccall(ptr, Any, (Any,), "foo")
+end
+@test ccall_reassigned_ptr(C_NULL) == "foo"
+
 # @threadcall functionality
 threadcall_test_func(x) =
  @threadcall((:testUcharX, libccalltest), Int32, (UInt8,), x % UInt8)