cmd/compile, types2: incorrect computation of unsafe.Sizeof() #45390
Labels
Milestone
Comments
|
Stand-alone reproducer: package main
import "unsafe"
func main() {
println(unsafe.Sizeof(RegArgs{}))
}
type RegArgs struct {
Ints [IntArgRegs]uintptr // untyped integer registers
Floats [FloatArgRegs]uint64 // untyped float registers
// Fields above this point are known to assembly.
// Ptrs is a space that duplicates Ints but with pointer type,
// used to make pointers passed or returned in registers
// visible to the GC by making the type unsafe.Pointer.
Ptrs [IntArgRegs]unsafe.Pointer
// ReturnIsPtr is a bitmap that indicates which registers
// contain or will contain pointers on the return path from
// a reflectcall. The i'th bit indicates whether the i'th
// register contains or will contain a valid Go pointer.
ReturnIsPtr IntArgRegBitmap
}
// IntArgRegBitmap is a bitmap large enough to hold one bit per
// integer argument/return register.
type IntArgRegBitmap [(IntArgRegs + 7) / 8]uint8
const IntArgRegs = 0
const FloatArgRegs = 0Running it: The relevant code is in // gc: The last field of a struct is not allowed to
// have size 0.
last := s.Sizeof(fields[n-1].Type())
if last == 0 {
last = 1
}This looks like an inconsistency in the compiler/compiler validation code. |
|
See also #9401 for background info. |
|
Commenting out those lines ( |
|
Change https://golang.org/cl/307549 mentions this issue: |
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
What version of Go are you using (
go version)?Current master (pre-release Go 1.17)
What did you do?
After building current master with ./make.bash, run:
I expected that to run normally, but I get this error:
This is from validation code in noder2. It looks like types2 is calculating unsafe.Sizeof(abi.RegArgs{}) as 8, when it should be zero. This only started failing when runtime/stack.go:1316 was added:
so the bug may have been around for a while (i.e. it wasn't a recent change in types2 that caused it to show up).
The text was updated successfully, but these errors were encountered: