runtime: memory corruption leading to panic on linux/riscv64

Go version

go version go1.26.1 linux/riscv64

Output of go env in your module/workspace:

AR='ar'
CC='cc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='c++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='riscv64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/home/buildozer/aports/community/opentofu/tmp/go'
GOCACHEPROG=''
GODEBUG=''
GOENV='/home/buildozer/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS='-buildmode=pie -modcacherw -trimpath -buildvcs=false'
GOGCCFLAGS='-fPIC -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/home/buildozer/aports/community/opentofu/tmp/go-build3937398104=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='riscv64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/dev/null'
GOMODCACHE='/home/buildozer/aports/community/opentofu/tmp/go'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/buildozer/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GORISCV64='rva20u64'
GOROOT='/usr/lib/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/buildozer/.config/go/telemetry'
GOTMPDIR='/home/buildozer/aports/community/opentofu/tmp'
GOTOOLCHAIN='local'
GOTOOLDIR='/usr/lib/go/pkg/tool/linux_riscv64'
GOVCS=''
GOVERSION='go1.26.1'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

Running the opentofu test suite on Alpine Linux on a riscv64 (MilkV Pioneer) , we run into a panic deep inside the fmt package.

panic: runtime error: invalid memory address or nil pointer dereference [recovered, repanicked]
[signal SIGSEGV: segmentation violation code=0x1 addr=0x1 pc=0x2aca9e6cfe]

goroutine 98 [running]:
testing.tRunner.func1.2({0x2acd5cf480, 0x2acdac1880})
        testing/testing.go:1974 +0x168
testing.tRunner.func1()
        testing/testing.go:1977 +0x244
panic({0x2acd5cf480?, 0x2acdac1880?})
        runtime/panic.go:860 +0x104
fmt.(*buffer).writeString(...)
        fmt/print.go:108
fmt.(*fmt).padString(0x2acaa532a2?, {0x1, 0x1})
        fmt/format.go:113 +0x86
fmt.(*fmt).fmtS(0x3f4757b828?, {0x1?, 0x7?})
        fmt/format.go:359 +0x42
fmt.(*pp).fmtString(0x0?, {0x1?, 0x0?}, 0x3?)
        fmt/print.go:498 +0xe2
fmt.(*pp).printArg(0x3f472ce9c0, {0x2acd4c2160, 0x3f47b81460}, 0x73)
        fmt/print.go:742 +0x4b0
fmt.(*pp).doPrintf(0x3f472ce9c0, {0x2acbe0f044, 0xf}, {0x3f46f9d7b8, 0x2, 0x2})
        fmt/print.go:1075 +0x2a2
fmt.Sprintf({0x2acbe0f044, 0xf}, {0x3f46f9d7b8, 0x2, 0x2})
        fmt/print.go:239 +0x4a
github.com/opentofu/opentofu/internal/addrs.Resource.String({{}, 0x47112da0, {0x1, 0x1}, {0x4d, 0x2acbe09ec0}})
        github.com/opentofu/opentofu/internal/addrs/resource.go:37 +0xf8
github.com/opentofu/opentofu/internal/addrs.ResourceInstance.String({{}, {{}, 0x47112da0, {0x1, 0x1}, {0x4d, 0x2acbe09ec0}}, {0x2acda53520, 0x2acda12200}})
        github.com/opentofu/opentofu/internal/addrs/resource.go:122 +0x74
github.com/opentofu/opentofu/internal/addrs.AbsResourceInstance.String({{}, {0x3f47112da0, 0x1, 0x1}, {{}, {{}, 0x47112da0, {0x1, 0x1}, {0x4d, ...}}, ...}})
        github.com/opentofu/opentofu/internal/addrs/resource.go:331 +0x92
github.com/opentofu/opentofu/internal/command/jsonentities.NewResourceAddr({{}, {0x3f47112da0, 0x1, 0x1}, {{}, {{}, 0x47112da0, {0x1, 0x1}, {0x4d, ...}}, ...}})
        github.com/opentofu/opentofu/internal/command/jsonentities/resource_addr.go:31 +0xfa
github.com/opentofu/opentofu/internal/command/jsonentities.NewResourceInstanceChange(0x3f46f9dd80)
        github.com/opentofu/opentofu/internal/command/jsonentities/change.go:38 +0x7cc
github.com/opentofu/opentofu/internal/command/views.TestJSONView_PlannedChange(0x3f471d0fc8)
        github.com/opentofu/opentofu/internal/command/views/json_view_test.go:198 +0x4ac
testing.tRunner(0x3f471d0fc8, 0x2acda0b918)
        testing/testing.go:2036 +0xc4
created by testing.(*T).Run in goroutine 1
        testing/testing.go:2101 +0x38a
FAIL    github.com/opentofu/opentofu/internal/command/views     1.270s

The panic starts from a code path that should never happen.

Printing PrevRunAddr in TestJSONView_PlannedChange results in the same panic.

Printing cs.PrevRunAddr.Resource.Resource.Mode shows: ResourceMode(1342943200), an invalid value. The value 77 (ascii 'M') is expected.

Interestingly, if I add managed.Instance(addrs.StringKey("boop")).Absolute(foo) (not assigning it, just a statement on its down), then the issue appears to fixed.

I'm happy to provide more details if necessary.

What did you see happen?

Failing test, panic, memory corruption

What did you expect to see?

None of the above