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e5060c7f75
Before this change, the check for too-large arrays (and other large types) occurred after escape analysis. If the data moved off stack and onto the heap contained any pointers, it would therefore escape, but because the too-large check occurred after escape analysis this would not be recorded and a stack pointer would leak to the heap (see the modified escape_array.go for an example). Some of these appear to remain, in calls to typecheck from within walk. Also corrected a few comments in escape_array.go about "BAD" analysis that is now done correctly. Enhanced to move aditional EscNone-but-large-so-heap checks into esc.c. Change-Id: I770c111baff28a9ed5f8beb601cf09dacc561b83 Reviewed-on: https://go-review.googlesource.com/10268 Reviewed-by: Russ Cox <rsc@golang.org>
123 lines
3.7 KiB
Go
123 lines
3.7 KiB
Go
// errorcheck -0 -m -l
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// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Test escape analysis for arrays and some large things
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package foo
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var Ssink *string
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type U [2]*string
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func bar(a, b *string) U { // ERROR "leaking param: a to result ~r2 level=0$" "leaking param: b to result ~r2 level=0$"
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return U{a, b}
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}
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func foo(x U) U { // ERROR "leaking param: x to result ~r1 level=0$"
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return U{x[1], x[0]}
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}
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func bff(a, b *string) U { // ERROR "leaking param: a to result ~r2 level=0$" "leaking param: b to result ~r2 level=0$"
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return foo(foo(bar(a, b)))
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}
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func tbff1() *string {
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a := "cat"
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b := "dog" // ERROR "moved to heap: b$"
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u := bff(&a, &b) // ERROR "tbff1 &a does not escape$" "tbff1 &b does not escape$"
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_ = u[0]
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return &b // ERROR "&b escapes to heap$"
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}
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// BAD: need fine-grained analysis to track u[0] and u[1] differently.
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func tbff2() *string {
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a := "cat" // ERROR "moved to heap: a$"
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b := "dog" // ERROR "moved to heap: b$"
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u := bff(&a, &b) // ERROR "&a escapes to heap$" "&b escapes to heap$"
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_ = u[0]
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return u[1]
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}
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func car(x U) *string { // ERROR "leaking param: x to result ~r1 level=0$"
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return x[0]
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}
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// BAD: need fine-grained analysis to track x[0] and x[1] differently.
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func fun(x U, y *string) *string { // ERROR "leaking param: x to result ~r2 level=0$" "leaking param: y to result ~r2 level=0$"
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x[0] = y
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return x[1]
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}
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func fup(x *U, y *string) *string { // ERROR "leaking param: x to result ~r2 level=1$" "leaking param: y$"
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x[0] = y // leaking y to heap is intended
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return x[1]
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}
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func fum(x *U, y **string) *string { // ERROR "leaking param: x to result ~r2 level=1$" "leaking param content: y$"
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x[0] = *y
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return x[1]
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}
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func fuo(x *U, y *U) *string { // ERROR "leaking param: x to result ~r2 level=1$" "leaking param content: y$"
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x[0] = y[0]
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return x[1]
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}
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// These two tests verify that:
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// small array literals are stack allocated;
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// pointers stored in small array literals do not escape;
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// large array literals are heap allocated;
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// pointers stored in large array literals escape.
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func hugeLeaks1(x **string, y **string) { // ERROR "leaking param content: x" "hugeLeaks1 y does not escape" "mark escaped content: x"
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a := [10]*string{*y}
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_ = a
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// 4 x 4,000,000 exceeds MaxStackVarSize, therefore it must be heap allocated if pointers are 4 bytes or larger.
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b := [4000000]*string{*x} // ERROR "moved to heap: b"
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_ = b
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}
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func hugeLeaks2(x *string, y *string) { // ERROR "leaking param: x" "hugeLeaks2 y does not escape"
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a := [10]*string{y}
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_ = a
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// 4 x 4,000,000 exceeds MaxStackVarSize, therefore it must be heap allocated if pointers are 4 bytes or larger.
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b := [4000000]*string{x} // ERROR "moved to heap: b"
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_ = b
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}
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// BAD: x need not leak.
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func doesNew1(x *string, y *string) { // ERROR "leaking param: x" "leaking param: y"
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a := new([10]*string) // ERROR "new\(\[10\]\*string\) does not escape"
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a[0] = x
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b := new([65537]*string) // ERROR "new\(\[65537\]\*string\) escapes to heap"
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b[0] = y
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}
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type a10 struct {
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s *string
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i [10]int32
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}
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type a65537 struct {
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s *string
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i [65537]int32
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}
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// BAD: x need not leak.
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func doesNew2(x *string, y *string) { // ERROR "leaking param: x" "leaking param: y"
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a := new(a10) // ERROR "new\(a10\) does not escape"
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a.s = x
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b := new(a65537) // ERROR "new\(a65537\) escapes to heap"
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b.s = y
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}
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// BAD: x need not leak.
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func doesMakeSlice(x *string, y *string) { // ERROR "leaking param: x" "leaking param: y"
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a := make([]*string, 10) // ERROR "make\(\[\]\*string, 10\) does not escape"
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a[0] = x
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b := make([]*string, 65537) // ERROR "make\(\[\]\*string, 65537\) escapes to heap"
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b[0] = y
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}
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