Allow subscripting raw pointers

This will be useful for dealing with vectors; regardless of our final solution
for the Index trait.

2016-07-06  Manish Goregaokar  <manish@mozilla.com>

gdb/ChangeLog:
    * rust-lang.c (rust_subscript): Allow subscripting pointers

gdb/testsuite/ChangeLog:
    * simple.rs: Add test for raw pointer subscripting
    * simple.exp: Add test expectations

gdb/ChangeLog

@@ -1,3 +1,7 @@
+2016-07-06  Manish Goregaokar  <manish@mozilla.com>
+
+	* rust-lang.c (rust_subscript): Allow subscripting pointers
+
 2016-07-05  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	* configure: Regenerate.

gdb/rust-lang.c

@@ -1415,6 +1415,12 @@ rust_subscript (struct expression *exp, int *pos, enum noside noside,
 	  low_bound = 0;
 	  high_bound = value_as_long (len);
 	}
+      else if (TYPE_CODE (type) == TYPE_CODE_PTR)
+	{
+	  base = lhs;
+	  low_bound = 0;
+	  high_bound = LONGEST_MAX;
+	}
       else
 	error (_("Cannot subscript non-array type"));
 

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2016-07-06  Manish Goregaokar  <manish@mozilla.com>
+
+	* simple.rs: Add test for raw pointer subscripting
+	* simple.exp: Add test expectations
+
 2016-07-05  Yao Qi  <yao.qi@linaro.org>
 
 	* gdb.mi/mi-reverse.exp: Match =record-started output.

gdb/testsuite/gdb.rust/simple.exp

@@ -73,6 +73,7 @@ gdb_test "print w" " = \\\[1, 2, 3, 4\\\]"
 gdb_test "ptype w" " = \\\[i32; 4\\\]"
 gdb_test "print w\[2\]" " = 3"
 gdb_test "print w\[2\] @ 2" " = \\\[3, 4\\\]"
+gdb_test "print w_ptr\[2\]" " = 3"
 gdb_test "print fromslice" " = 3"
 gdb_test "print slice\[0\]" " = 3"
 gdb_test "print slice as &\[i32\]\[0\]" " = 3"

gdb/testsuite/gdb.rust/simple.rs

@@ -87,6 +87,7 @@ fn main () {
 
     let v = Something::Three;
     let w = [1,2,3,4];
+    let w_ptr = &w[0];
     let x = (23, 25.5);
     let y = HiBob {field1: 7, field2: 8};
     let z = ByeBob(7, 8);