Use std::string in Rust code

This changes a couple of spots in the Rust support to use std::string.
In one spot this removes some manual memory management; in the other
spot this allows the removal of a call to xstrdup.

2017-02-02  Tom Tromey  <tom@tromey.com>

	* rust-lang.h (rust_crate_for_block): Update.
	* rust-lang.c (rust_crate_for_block): Return std::string.
	(rust_get_disr_info): Use std:;string, not
	gdb::unique_xmalloc_ptr.
	* rust-exp.y (crate_name): Update.

1 files changed, 6 insertions, 8 deletions

diff --git a/gdb/rust-lang.c b/gdb/rust-lang.c
index dd72cd9..17df6bb 100644
--- a/gdb/rust-lang.c
+++ b/gdb/rust-lang.c
@@ -51,19 +51,17 @@ rust_last_path_segment (const char * path)
   return result + 1;
 }
 
-/* Find the Rust crate for BLOCK.  If no crate can be found, returns
-   NULL.  Otherwise, returns a newly allocated string that the caller
-   is responsible for freeing.  */
+/* See rust-lang.h.  */
 
-char *
+std::string
 rust_crate_for_block (const struct block *block)
 {
   const char *scope = block_scope (block);
 
   if (scope[0] == '\0')
-    return NULL;
+    return std::string ();
 
-  return xstrndup (scope, cp_find_first_component (scope));
+  return std::string (scope, cp_find_first_component (scope));
 }
 
 /* Information about the discriminant/variant of an enum */
@@ -157,8 +155,8 @@ rust_get_disr_info (struct type *type, const gdb_byte *valaddr,
       /* Optimized enums have only one field.  */
       member_type = TYPE_FIELD_TYPE (type, 0);
 
-      gdb::unique_xmalloc_ptr<char> name (xstrdup (TYPE_FIELD_NAME (type, 0)));
-      tail = name.get () + strlen (RUST_ENUM_PREFIX);
+      std::string name (TYPE_FIELD_NAME (type, 0));
+      tail = &name[0] + strlen (RUST_ENUM_PREFIX);
 
       /* The location of the value that doubles as a discriminant is
          stored in the name of the field, as