Fix -Wmaybe-uninitialized

../namespace.c: In function ‘current_namespace’:
../namespace.c:221:48: warning: ‘proc_ns’ may be used uninitialized [-Wmaybe-uninitialized]
  221 |                     if (permit_calling_builtin || (proc_ns && NAMESPACE_USER_P(proc_ns)))
      |                         ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../namespace.c:204:31: note: ‘proc_ns’ was declared here
  204 |         const rb_namespace_t *proc_ns;
      |                               ^~~~~~~

In function ‘copy_ext_file’,
    inlined from ‘rb_namespace_local_extension’ at ../namespace.c:855:18:
../namespace.c:768:21: warning: ‘written’ may be used uninitialized [-Wmaybe-uninitialized]
  768 |             wrote = fwrite(buffer+written, 1, read-written, dst);
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../namespace.c: In function ‘rb_namespace_local_extension’:
../namespace.c:748:25: note: ‘written’ was declared here
  748 |     size_t read, wrote, written;
      |                         ^~~~~~~

In function ‘copy_ext_file’,
    inlined from ‘rb_namespace_local_extension’ at ../namespace.c:855:18:
../namespace.c:768:21: warning: ‘read’ may be used uninitialized [-Wmaybe-uninitialized]
  768 |             wrote = fwrite(buffer+written, 1, read-written, dst);
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../namespace.c: In function ‘rb_namespace_local_extension’:
../namespace.c:748:12: note: ‘read’ was declared here
  748 |     size_t read, wrote, written;
      |            ^~~~

Author: k0kubun

namespace.c

@@ -201,7 +201,7 @@ current_namespace(bool permit_calling_builtin)
         // calling = 0;
     }
     while (calling) {
-        const rb_namespace_t *proc_ns;
+        const rb_namespace_t *proc_ns = NULL;
         VALUE bh;
         if (VM_FRAME_NS_SWITCH_P(cfp)) {
             bh = rb_vm_frame_block_handler(cfp);
@@ -745,7 +745,7 @@ copy_ext_file(char *src_path, char *dst_path)
 #else
     FILE *src, *dst;
     char buffer[1024];
-    size_t read, wrote, written;
+    size_t read = 0, wrote, written = 0;
     size_t maxread = sizeof(buffer);
     int eof = 0;
     int clean_read = 1;