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Go patch committed: Copy array in range statement

Message ID CAOyqgcUA0v9BLu3xVa6bvo0LZ8wwr+JJLkG5jE41mhCT7zeyGA@mail.gmail.com
State New
Headers show

Commit Message

Ian Lance Taylor Dec. 23, 2014, 6:39 p.m. UTC 
The Go frontend failed to copy an array in a range statement.  The
effect was that if the code in the loop changed future elements of the
original array, it would incorrectly change the results of the
iteration.  This patch from Chris Manghane fixes the problem.  This
issue 34 in the gofrontend issue tracker.  Bootstrapped and ran Go
testsuite on x86_64-unknown-linux-gnu.  Committed to mainline.

Ian
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Patch

diff -r 738f975a6972 go/statements.cc
--- a/go/statements.cc	Fri Dec 19 14:18:12 2014 -0800
+++ b/go/statements.cc	Tue Dec 23 10:36:47 2014 -0800
@@ -5558,8 +5558,9 @@ 
 
   // The loop we generate:
   //   len_temp := len(range)
+  //   range_temp := range
   //   for index_temp = 0; index_temp < len_temp; index_temp++ {
-  //           value_temp = range[index_temp]
+  //           value_temp = range_temp[index_temp]
   //           index = index_temp
   //           value = value_temp
   //           original body
@@ -5573,9 +5574,11 @@ 
   Block* init = new Block(enclosing, loc);
 
   Expression* ref = this->make_range_ref(range_object, range_temp, loc);
+  range_temp = Statement::make_temporary(NULL, ref, loc);
   Expression* len_call = this->call_builtin(gogo, "len", ref, loc);
   Temporary_statement* len_temp = Statement::make_temporary(index_temp->type(),
 							    len_call, loc);
+  init->add_statement(range_temp);
   init->add_statement(len_temp);
 
   Expression* zexpr = Expression::make_integer_ul(0, NULL, loc);
@@ -5605,7 +5608,7 @@ 
     {
       iter_init = new Block(body_block, loc);
 
-      ref = this->make_range_ref(range_object, range_temp, loc);
+      ref = Expression::make_temporary_reference(range_temp, loc);
       Expression* ref2 = Expression::make_temporary_reference(index_temp, loc);
       Expression* index = Expression::make_index(ref, ref2, NULL, NULL, loc);