cmd/link: correctly decode name length

The linker was incorrectly decoding type name lengths, causing
typelinks to be sorted out of order and in cases where the name was
the exact right length, linker panics.

Added a test to the reflect package that causes TestTypelinksSorted
to fail before this CL. It's not the exact failure seen in #15448
but it has the same cause: decodetype_name calculating the wrong
length.

The equivalent decoders in reflect/type.go and runtime/type.go
have the parenthesis in the right place.

Fixes #15448

Change-Id: I33257633d812b7d2091393cb9d6cc8a73e0138c8
Reviewed-on: https://go-review.googlesource.com/22403
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/cmd/link/internal/ld/decodesym.go b/src/cmd/link/internal/ld/decodesym.go
index 3ec488bbe8da0fd23e367aecc5a47cc33d338363..551ff802d7fb69c910e4b31795c30a5c6d7b9bab 100644 (file)
--- a/src/cmd/link/internal/ld/decodesym.go
+++ b/src/cmd/link/internal/ld/decodesym.go
@@ -239,7 +239,7 @@ func decodetype_name(s *LSym, off int) string {
        }
 
        data := r.Sym.P
-       namelen := int(uint16(data[1]<<8) | uint16(data[2]))
+       namelen := int(uint16(data[1])<<8 | uint16(data[2]))
        return string(data[3 : 3+namelen])
 }
 

diff --git a/src/reflect/all_test.go b/src/reflect/all_test.go
index e88bc880e2eccd2b62567bf01e886a7c0f3b21d2..aff8ea253b90cea18069b03b65e3cc1b770b143e 100644 (file)
--- a/src/reflect/all_test.go
+++ b/src/reflect/all_test.go
@@ -5651,6 +5651,8 @@ func TestChanAlloc(t *testing.T) {
        // allocs < 0.5 condition will trigger and this test should be fixed.
 }
 
+type TheNameOfThisTypeIsExactly255BytesLongSoWhenTheCompilerPrependsTheReflectTestPackageNameAndExtraStarTheLinkerRuntimeAndReflectPackagesWillHaveToCorrectlyDecodeTheSecondLengthByte0123456789_0123456789_0123456789_0123456789_0123456789_012345678 int
+
 type nameTest struct {
        v    interface{}
        want string
@@ -5664,6 +5666,7 @@ var nameTests = []nameTest{
        {(func() D1)(nil), ""},
        {(<-chan D1)(nil), ""},
        {(chan<- D1)(nil), ""},
+       {TheNameOfThisTypeIsExactly255BytesLongSoWhenTheCompilerPrependsTheReflectTestPackageNameAndExtraStarTheLinkerRuntimeAndReflectPackagesWillHaveToCorrectlyDecodeTheSecondLengthByte0123456789_0123456789_0123456789_0123456789_0123456789_012345678(0), "TheNameOfThisTypeIsExactly255BytesLongSoWhenTheCompilerPrependsTheReflectTestPackageNameAndExtraStarTheLinkerRuntimeAndReflectPackagesWillHaveToCorrectlyDecodeTheSecondLengthByte0123456789_0123456789_0123456789_0123456789_0123456789_012345678"},
 }
 
 func TestNames(t *testing.T) {