Nir Soffer
2022-Jun-09 17:10 UTC
[Libguestfs] [PATCH libnbd] golang: aio_buffer.go: Explicit panic() on invalid usage
Previously we depended on the behavior on common platforms to panic when
trying to use a nil pointer, but Richard reported that it segfault on
RISC-V. Avoid the undocumented assumptions and panic explicitly with a
useful panic message.
Signed-off-by: Nir Soffer <nsoffer at redhat.com>
---
golang/aio_buffer.go | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/golang/aio_buffer.go b/golang/aio_buffer.go
index 52ea54de..325dbc98 100644
--- a/golang/aio_buffer.go
+++ b/golang/aio_buffer.go
@@ -65,28 +65,37 @@ func (b *AioBuffer) Free() {
if b.P != nil {
C.free(b.P)
b.P = nil
}
}
// Bytes copies the underlying C array to Go allocated memory and return a
// slice. Modifying the returned slice does not modify the underlying buffer
// backing array.
func (b *AioBuffer) Bytes() []byte {
+ if b.P == nil {
+ panic("Using AioBuffer after Free()")
+ }
return C.GoBytes(b.P, C.int(b.Size))
}
// Slice creates a slice backed by the underlying C array. The slice can be
// used to access or modify the contents of the underlying array. The slice
// must not be used after caling Free().
func (b *AioBuffer) Slice() []byte {
+ if b.P == nil {
+ panic("Using AioBuffer after Free()")
+ }
// See https://github.com/golang/go/wiki/cgo#turning-c-arrays-into-go-slices
// TODO: Use unsafe.Slice() when we require Go 1.17.
return (*[1<<30]byte)(b.P)[:b.Size:b.Size]
}
// Get returns a pointer to a byte in the underlying C array. The pointer can
// be used to modify the underlying array. The pointer must not be used after
// calling Free().
func (b *AioBuffer) Get(i uint) *byte {
+ if b.P == nil {
+ panic("Using AioBuffer after Free()")
+ }
return (*byte)(unsafe.Pointer(uintptr(b.P) + uintptr(i)))
}
--
2.36.1
Richard W.M. Jones
2022-Jun-09 17:44 UTC
[Libguestfs] [PATCH libnbd] golang: aio_buffer.go: Explicit panic() on invalid usage
On Thu, Jun 09, 2022 at 08:10:53PM +0300, Nir Soffer wrote:> Previously we depended on the behavior on common platforms to panic when > trying to use a nil pointer, but Richard reported that it segfault on > RISC-V. Avoid the undocumented assumptions and panic explicitly with a > useful panic message. > > Signed-off-by: Nir Soffer <nsoffer at redhat.com>I tested this on RISC-V and it fixes the tests, so I pushed it, thanks. BTW this doesn't fix the cgocheck=2 problem, I still have to disable that line in run.in (on RISC-V). Rich.> golang/aio_buffer.go | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/golang/aio_buffer.go b/golang/aio_buffer.go > index 52ea54de..325dbc98 100644 > --- a/golang/aio_buffer.go > +++ b/golang/aio_buffer.go > @@ -65,28 +65,37 @@ func (b *AioBuffer) Free() { > if b.P != nil { > C.free(b.P) > b.P = nil > } > } > > // Bytes copies the underlying C array to Go allocated memory and return a > // slice. Modifying the returned slice does not modify the underlying buffer > // backing array. > func (b *AioBuffer) Bytes() []byte { > + if b.P == nil { > + panic("Using AioBuffer after Free()") > + } > return C.GoBytes(b.P, C.int(b.Size)) > } > > // Slice creates a slice backed by the underlying C array. The slice can be > // used to access or modify the contents of the underlying array. The slice > // must not be used after caling Free(). > func (b *AioBuffer) Slice() []byte { > + if b.P == nil { > + panic("Using AioBuffer after Free()") > + } > // See https://github.com/golang/go/wiki/cgo#turning-c-arrays-into-go-slices > // TODO: Use unsafe.Slice() when we require Go 1.17. > return (*[1<<30]byte)(b.P)[:b.Size:b.Size] > } > > // Get returns a pointer to a byte in the underlying C array. The pointer can > // be used to modify the underlying array. The pointer must not be used after > // calling Free(). > func (b *AioBuffer) Get(i uint) *byte { > + if b.P == nil { > + panic("Using AioBuffer after Free()") > + } > return (*byte)(unsafe.Pointer(uintptr(b.P) + uintptr(i))) > } > -- > 2.36.1-- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW