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gc: avoid meaningless constant overflow error for inverted slice range 

Used to say:

issue4251.go:12: inverted slice range
issue4251.go:12: constant -1 overflows uint64
issue4251.go:16: inverted slice range
issue4251.go:16: constant -1 overflows uint64
issue4251.go:20: inverted slice range
issue4251.go:20: constant -1 overflows uint64

With this patch, only gives the "inverted slice range" errors.

R=golang-dev, daniel.morsing
CC=golang-dev
https://golang.org/cl/6871058
This commit is contained in:
Ian Lance Taylor 2012-12-05 15:46:45 -08:00
parent 54e8d504e8
commit 08918ba438
3 changed files with 43 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
src/cmd/gc/typecheck.c
View File

@ -950,12 +950,16 @@ reswitch:
goto error;
}
if(n->right->left->op == OLITERAL) {
if(mpgetfix(n->right->left->val.u.xval) < 0)
if(mpgetfix(n->right->left->val.u.xval) < 0) {
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)
goto error;
} 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)
goto error;
} else if(mpcmpfixfix(n->right->left->val.u.xval, maxintval[TINT]) > 0) {
yyerror("invalid slice index %N (index too large)", n->right->left);
goto error;
}
}
}
if(n->right->right != N) {
@ -966,14 +970,26 @@ reswitch:
goto error;
}
if(n->right->right->op == OLITERAL) {
if(mpgetfix(n->right->right->val.u.xval) < 0)
if(mpgetfix(n->right->right->val.u.xval) < 0) {
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)
goto error;
} 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)
goto error;
} else if(mpcmpfixfix(n->right->right->val.u.xval, maxintval[TINT]) > 0) {
yyerror("invalid slice index %N (index too large)", n->right->right);
goto error;
}
}
}
if(n->right->left != N
&& n->right->right != N
&& n->right->left->op == OLITERAL
&& n->right->right->op == OLITERAL
&& mpcmpfixfix(n->right->left->val.u.xval, n->right->right->val.u.xval) > 0) {
yyerror("inverted slice index %N > %N", n->right->left, n->right->right);
goto error;
}
goto ret;
/*

4
src/cmd/gc/walk.c
View File

@ -2517,8 +2517,6 @@ sliceany(Node* n, NodeList **init)
else
bv = mpgetfix(bound->val.u.xval);
}
lbv = -1;
hbv = -1;
if(isconst(hb, CTINT)) {
hbv = mpgetfix(hb->val.u.xval);
@ -2536,8 +2534,6 @@ sliceany(Node* n, NodeList **init)
if(lbv == 0)
lb = N;
}
if(lbv >= 0 && hbv >= 0 && lbv > hbv)
yyerror("inverted slice range");
// dynamic checks convert all bounds to unsigned to save us the bound < 0 comparison
// generate

21
test/fixedbugs/issue4251.go Normal file
View File

@ -0,0 +1,21 @@
// errorcheck
// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Issue 4251: slice with inverted range is an error.
package p
func F1(s []byte) []byte {
return s[2:1] // ERROR "inverted"
}
func F2(a [10]byte) []byte {
return a[2:1] // ERROR "inverted"
}
func F3(s string) string {
return s[2:1] // ERROR "inverted"
}