Fixed visibility of undeclared functions and objects.

test/misc/bug2304-implicit-func.c

@@ -0,0 +1,21 @@
+/* Bug 2304 - Visibility of objects/functions undeclared in file scope but 'extern'-declared in unrelated block scopes */
+
+/* This one should fail even in C89 */
+
+void f1(void)
+{
+    extern unsigned int f();
+}
+
+/* 'f' is still invisible in the file scope */
+
+int main(void)
+{
+    f();        /* Should be a conflict since the implicit function type is incompatible */
+    return 0;
+}
+
+unsigned int f()
+{
+    return 42;
+}