Teach the dwarf readers to handle udata, so we can link with util.option; add util.rs to std.rc.

src/boot/me/dwarf.ml

@@ -2724,6 +2724,7 @@ let read_dies
                           | DW_FORM_data1 -> DATA_num (ar.asm_get_u8())
                           | DW_FORM_data4 -> DATA_num (ar.asm_get_u32())
                           | DW_FORM_flag -> DATA_num (ar.asm_get_u8())
+                          | DW_FORM_udata -> DATA_num (ar.asm_get_uleb())
                           | DW_FORM_block1 -> (adv_block1(); DATA_other)
                           | DW_FORM_block4 -> (adv_block4(); DATA_other)
                           | _ ->

src/lib/std.rc

@@ -16,6 +16,10 @@ mod _str;
 mod _io;
 mod sys;
 
+// Utility modules.
+
+mod util;
+
 // Authorize various rule-bendings.
 
 auth _io = unsafe;

src/rt/rust_crate_reader.cpp

@@ -347,6 +347,11 @@ rust_crate_reader::die::step_attr(attr &a) const
       return rdr->is_ok() || rdr->at_end();
       break;
 
+    case DW_FORM_udata:
+      rdr->get_uleb(u32);
+      return rdr->is_ok() || rdr->at_end();
+      break;
+
     default:
       rdr->mem.dom->log(rust_log::DWARF, "  unknown dwarf form: 0x%"
                         PRIxPTR, a.form);