From: Brad Fitzpatrick <bradfitz@golang.org>
Date: Thu, 1 Mar 2018 22:22:44 +0000 (+0000)
Subject: Revert "runtime: use bytes.IndexByte in findnull"
X-Git-Tag: go1.11beta1~1380
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=1fadbc1a76b2d9a11453ef4e21b77c353493ac2c;p=gostls13.git

Revert "runtime: use bytes.IndexByte in findnull"

This reverts commit 7365fac2dbd01960268ee051ed03d961258d4ef4.

Reason for revert: breaks the build on some architectures, reading unmapped pages?

Change-Id: I3a8c02dc0b649269faacea79ecd8213defa97c54
Reviewed-on: https://go-review.googlesource.com/97995
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
---

diff --git a/misc/cgo/test/basic.go b/misc/cgo/test/basic.go
index 2655a66e38..3ceb4ce847 100644
--- a/misc/cgo/test/basic.go
+++ b/misc/cgo/test/basic.go
@@ -31,8 +31,6 @@ struct S {
 	int x;
 };
 
-const char *cstr = "abcefghijklmnopqrstuvwxyzABCEFGHIJKLMNOPQRSTUVWXYZ1234567890";
-
 extern enum E myConstFunc(struct S* const ctx, int const id, struct S **const filter);
 
 enum E myConstFunc(struct S *const ctx, int const id, struct S **const filter) { return 0; }
@@ -151,18 +149,6 @@ func benchCgoCall(b *testing.B) {
 	}
 }
 
-var sinkString string
-
-func benchGoString(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		sinkString = C.GoString(C.cstr)
-	}
-	const want = "abcefghijklmnopqrstuvwxyzABCEFGHIJKLMNOPQRSTUVWXYZ1234567890"
-	if sinkString != want {
-		b.Fatalf("%q != %q", sinkString, want)
-	}
-}
-
 // Issue 2470.
 func testUnsignedInt(t *testing.T) {
 	a := (int64)(C.UINT32VAL)
diff --git a/misc/cgo/test/cgo_test.go b/misc/cgo/test/cgo_test.go
index 01ab7eba5e..cfacb9c40d 100644
--- a/misc/cgo/test/cgo_test.go
+++ b/misc/cgo/test/cgo_test.go
@@ -88,5 +88,4 @@ func Test6907Go(t *testing.T)                { test6907Go(t) }
 func Test21897(t *testing.T)                 { test21897(t) }
 func Test22906(t *testing.T)                 { test22906(t) }
 
-func BenchmarkCgoCall(b *testing.B)  { benchCgoCall(b) }
-func BenchmarkGoString(b *testing.B) { benchGoString(b) }
+func BenchmarkCgoCall(b *testing.B) { benchCgoCall(b) }
diff --git a/src/runtime/error.go b/src/runtime/error.go
index 2435f98b7a..e1291e1543 100644
--- a/src/runtime/error.go
+++ b/src/runtime/error.go
@@ -121,7 +121,6 @@ func printany(i interface{}) {
 // strings.IndexByte is implemented in runtime/asm_$goarch.s
 // but amusingly we need go:linkname to get access to it here in the runtime.
 //go:linkname stringsIndexByte strings.IndexByte
-//go:noescape
 func stringsIndexByte(s string, c byte) int
 
 // panicwrap generates a panic for a call to a wrapped value method
diff --git a/src/runtime/string.go b/src/runtime/string.go
index 0ea162235c..5c83895995 100644
--- a/src/runtime/string.go
+++ b/src/runtime/string.go
@@ -407,9 +407,12 @@ func findnull(s *byte) int {
 	if s == nil {
 		return 0
 	}
-	ss := stringStruct{unsafe.Pointer(s), maxAlloc/2 - 1}
-	t := *(*string)(unsafe.Pointer(&ss))
-	return stringsIndexByte(t, 0)
+	p := (*[maxAlloc/2 - 1]byte)(unsafe.Pointer(s))
+	l := 0
+	for p[l] != 0 {
+		l++
+	}
+	return l
 }
 
 func findnullw(s *uint16) int {