cmd/gc: warn about slice indexes larger than int in typecheck pass

Fixes GOARCH=386 build.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6810098

diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index 9b42772393d66f0866ba005beb358b2acb572288..2d1dbd75f1b23eda450204a390e7fbdf4841f3af 100644 (file)
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -828,6 +828,10 @@ reswitch:
                                        yyerror("invalid %s index %N (index must be non-negative)", why, n->right);
                                } else if(isfixedarray(t) && t->bound > 0 && mpgetfix(n->right->val.u.xval) >= t->bound)
                                        yyerror("invalid array index %N (out of bounds for %d-element array)", n->right, t->bound);
+                               else if(mpcmpfixfix(n->right->val.u.xval, maxintval[TINT]) > 0) {
+                                       why = isfixedarray(t) ? "array" : "slice";
+                                       yyerror("invalid %s index %N (index too large)", why, n->right);
+                               }
                        }
                        break;
 
@@ -947,6 +951,8 @@ reswitch:
                                        yyerror("invalid slice index %N (index must be non-negative)", n->right->left);
                                else if(tp != nil && tp->bound > 0 && mpgetfix(n->right->left->val.u.xval) > tp->bound)
                                        yyerror("invalid slice index %N (out of bounds for %d-element array)", n->right->left, tp->bound);
+                               else if(mpcmpfixfix(n->right->left->val.u.xval, maxintval[TINT]) > 0)
+                                       yyerror("invalid slice index %N (index too large)", n->right->left);
                        }
                }
                if(n->right->right != N) {
@@ -961,6 +967,8 @@ reswitch:
                                        yyerror("invalid slice index %N (index must be non-negative)", n->right->right);
                                else if(tp != nil && tp->bound > 0 && mpgetfix(n->right->right->val.u.xval) > tp->bound)
                                        yyerror("invalid slice index %N (out of bounds for %d-element array)", n->right->right, tp->bound);
+                               else if(mpcmpfixfix(n->right->right->val.u.xval, maxintval[TINT]) > 0)
+                                       yyerror("invalid slice index %N (index too large)", n->right->right);
                        }
                }
                goto ret;