log/slog: nil pointer dereference when printing nil regexp #61648
Description
What version of Go are you using (go version)?
$ go1.21rc3 linux/amd64
Does this issue reproduce with the latest release?
Yes – this is indeed a regression from using go1.20 + exp/slog
What did you do?
Log in a simple nil value using slog
https://go.dev/play/p/jAg4xDbs4sn?v=gotip
What did you expect to see?
A formatted nil line, as per https://go.dev/play/p/b7Vjf1L09sC
2009/11/10 23:00:00 INFO priting re=<nil>
What did you see instead?
Crash, with nil pointer deref
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x4afbee]
goroutine 1 [running]:
regexp.(*Regexp).String(...)
/usr/local/go-faketime/src/regexp/regexp.go:110
regexp.(*Regexp).MarshalText(0x0?)
/usr/local/go-faketime/src/regexp/regexp.go:1294 +0xe
log/slog.appendTextValue(0xc000051a60, {{}, 0x4cf000?, {0x4cf000?, 0x0?}})
/usr/local/go-faketime/src/log/slog/text_handler.go:106 +0x28e
log/slog.(*handleState).appendValue(0xc000051a60, {{}, 0x4d2164?, {0x4cf000?, 0x0?}})
/usr/local/go-faketime/src/log/slog/handler.go:519 +0x31
log/slog.(*handleState).appendAttr(0xc000051a60, {{0x4d2164, 0x2}, {{}, 0x0, {0x4cf000, 0x0}}})
/usr/local/go-faketime/src/log/slog/handler.go:475 +0x7ea
log/slog.(*handleState).appendNonBuiltIns.func1({{0x4d2164, 0x2}, {{}, 0x0, {0x4cf000, 0x0}}})
/usr/local/go-faketime/src/log/slog/handler.go:326 +0x49
log/slog.Record.Attrs({{0xbab699fc00000000, 0x1, 0x586660}, {0x4d2586, 0x7}, 0x0, 0x4afd1c, {{{0x4d2164, 0x2}, {{...}, ...}}, ...}, ...}, ...)
/usr/local/go-faketime/src/log/slog/record.go:84 +0xc4
log/slog.(*handleState).appendNonBuiltIns(_, {{0xbab699fc00000000, 0x1, 0x586660}, {0x4d2586, 0x7}, 0x0, 0x4afd1c, {{{0x4d2164, 0x2}, ...}, ...}, ...})
/usr/local/go-faketime/src/log/slog/handler.go:325 +0x465
log/slog.(*defaultHandler).Handle(_, {_, _}, {{0xbab699fc00000000, 0x1, 0x586660}, {0x4d2586, 0x7}, 0x0, 0x4afd1c, ...})
/usr/local/go-faketime/src/log/slog/handler.go:115 +0x385
log/slog.(*Logger).log(0xc000014090, {0x4f75f0, 0x5b3f80}, 0x0, {0x4d2586, 0x7}, {0xc00007af10, 0x2, 0x2})
/usr/local/go-faketime/src/log/slog/logger.go:225 +0x1e4
log/slog.Info({0x4d2586?, 0xc00003e730?}, {0xc00003e710?, 0x60?, 0x0?})
/usr/local/go-faketime/src/log/slog/logger.go:260 +0x91
main.main()
/tmp/sandbox2138239418/prog.go:10 +0x5c
Program exited.