x/tools/cmd/deadcode: impossible SIGSEGV in darwin-amd64-race test

[gopherbot]

#!watchflakes
default <- pkg == "golang.org/x/tools/cmd/deadcode" && test == "Test/testdata/basic.txtar/L3"

Issue created automatically to collect these failures.

Example (log):

=== RUN   Test/testdata/basic.txtar/L3
    deadcode_test.go:115: deadcode failed: exit status 2 (stderr=unexpected fault address 0xb01dfacedebac1e
        fatal error: fault
        [signal SIGSEGV: segmentation violation code=0x1 addr=0xb01dfacedebac1e pc=0x467613a]
        
        goroutine 506 gp=0xc000edb880 m=3 mp=0xc000080008 [running]:
        runtime.throw({0x46da455?, 0x20?})
        	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/panic.go:1073 +0x48 fp=0xc0027d5bd0 sp=0xc0027d5ba0 pc=0x429b4c8
        runtime.sigpanic()
        	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/signal_unix.go:931 +0x26a fp=0xc0027d5c30 sp=0xc0027d5bd0 pc=0x429d42a
...
        golang.org/x/tools/go/ssa.(*Program).Build.func1(0xc0010b6f98?)
        	/Users/swarming/.swarming/w/ir/x/w/targetrepo3138335219/go/ssa/builder.go:3142 +0x45 fp=0xc004365fc8 sp=0xc004365f90 pc=0x4679405
        golang.org/x/tools/go/ssa.(*Program).Build.gowrap1()
        	/Users/swarming/.swarming/w/ir/x/w/targetrepo3138335219/go/ssa/builder.go:3145 +0x24 fp=0xc004365fe0 sp=0xc004365fc8 pc=0x4679384
        runtime.goexit({})
        	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/asm_amd64.s:1700 +0x1 fp=0xc004365fe8 sp=0xc004365fe0 pc=0x42a3d01
        created by golang.org/x/tools/go/ssa.(*Program).Build in goroutine 1
        	/Users/swarming/.swarming/w/ir/x/w/targetrepo3138335219/go/ssa/builder.go:3141 +0x195
        )
--- FAIL: Test/testdata/basic.txtar/L3 (2.93s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "golang.org/x/tools/cmd/deadcode" && test == "Test/testdata/basic.txtar/L3"

2025-03-10 16:39 x_tools-go1.23-darwin-amd64-race tools@03f197e9 release-branch.go1.23@45aade7f x/tools/cmd/deadcode.Test/testdata/basic.txtar/L3 (log)

=== RUN   Test/testdata/basic.txtar/L3
    deadcode_test.go:115: deadcode failed: exit status 2 (stderr=unexpected fault address 0xb01dfacedebac1e
        fatal error: fault
        [signal SIGSEGV: segmentation violation code=0x1 addr=0xb01dfacedebac1e pc=0x467613a]
        
        goroutine 506 gp=0xc000edb880 m=3 mp=0xc000080008 [running]:
        runtime.throw({0x46da455?, 0x20?})
        	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/panic.go:1073 +0x48 fp=0xc0027d5bd0 sp=0xc0027d5ba0 pc=0x429b4c8
        runtime.sigpanic()
        	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/signal_unix.go:931 +0x26a fp=0xc0027d5c30 sp=0xc0027d5bd0 pc=0x429d42a
...
        golang.org/x/tools/go/ssa.(*Program).Build.func1(0xc0010b6f98?)
        	/Users/swarming/.swarming/w/ir/x/w/targetrepo3138335219/go/ssa/builder.go:3142 +0x45 fp=0xc004365fc8 sp=0xc004365f90 pc=0x4679405
        golang.org/x/tools/go/ssa.(*Program).Build.gowrap1()
        	/Users/swarming/.swarming/w/ir/x/w/targetrepo3138335219/go/ssa/builder.go:3145 +0x24 fp=0xc004365fe0 sp=0xc004365fc8 pc=0x4679384
        runtime.goexit({})
        	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/asm_amd64.s:1700 +0x1 fp=0xc004365fe8 sp=0xc004365fe0 pc=0x42a3d01
        created by golang.org/x/tools/go/ssa.(*Program).Build in goroutine 1
        	/Users/swarming/.swarming/w/ir/x/w/targetrepo3138335219/go/ssa/builder.go:3141 +0x195
        )
--- FAIL: Test/testdata/basic.txtar/L3 (2.93s)

— watchflakes

[adonovan]

Unexpected SIGSEGV in code that "can't fail". Suspicious fault address 0xb01dfacedebac1e (indicating that the actual address was not a valid amd64 address with the top 16 bits all zeros or ones). This is either bad hardware or a compiler/runtime bug.

func (b *builder) stmtList(fn *Function, list []ast.Stmt) {
	for _, s := range list { <--------- panic
		b.stmt(fn, s)
	}
}

    deadcode_test.go:115: deadcode failed: exit status 2 (stderr=unexpected fault address 0xb01dfacedebac1e
        fatal error: fault
        [signal SIGSEGV: segmentation violation code=0x1 addr=0xb01dfacedebac1e pc=0x467613a]
        
        goroutine 506 gp=0xc000edb880 m=3 mp=0xc000080008 [running]:
        runtime.throw({0x46da455?, 0x20?})
        	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/panic.go:1073 +0x48 fp=0xc0027d5bd0 sp=0xc0027d5ba0 pc=0x429b4c8
        runtime.sigpanic()
        	/Users/swarming/.swarming/w/ir/x/w/goroot/src/runtime/signal_unix.go:931 +0x26a fp=0xc0027d5c30 sp=0xc0027d5bd0 pc=0x429d42a
        golang.org/x/tools/go/ssa.(*builder).stmtList(...)
        	/Users/swarming/.swarming/w/ir/x/w/targetrepo3138335219/go/ssa/builder.go:965
        golang.org/x/tools/go/ssa.(*builder).stmt(0xc00857e360, 0xc0083da000, {0x48a1468?, 0xc004d350b1?})
        	/Users/swarming/.swarming/w/ir/x/w/targetrepo3138335219/go/ssa/builder.go:2747 +0x103a fp=0xc0027d5d60 sp=0xc0027d5c30 pc=0x467613a
...