From bf0b605dfbc36b3555eef3315b15facca1c08bdb Mon Sep 17 00:00:00 2001 From: Alan Donovan Date: Thu, 9 May 2024 18:16:59 -0400 Subject: runtime: make convTstring write barrier unreachable from throw CL 581215 changed 'throw' so that instead of print(s) it called a more complicated function, printpanicval, that statically appeared to have convTstring in its call graph, even though this isn't dynamically reachable when called with a string argument. However, this caused the link-time static callgraph test to point out that throw (which is called in nowritebarrierrec contexts such as markgc) reaches a write barrier. The solution is to inline and specialize the printpanicval function for strings; it reduces to printindented. Thanks to mpratt for pointing out that the reachability check is on the fully lowered code, and is thus sensitive to optimizations such as inlining. I added an explanatory comment on the line that generates the error message to help future users confused as I was. Fixes golang/go#67274 Change-Id: Ief110d554de365ce4c09509dceee000cbee30ad9 Reviewed-on: https://go-review.googlesource.com/c/go/+/584617 Reviewed-by: Than McIntosh LUCI-TryBot-Result: Go LUCI Reviewed-by: Michael Pratt --- src/runtime/panic.go | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'src/runtime/panic.go') diff --git a/src/runtime/panic.go b/src/runtime/panic.go index 122fc30df2..ff9c64113f 100644 --- a/src/runtime/panic.go +++ b/src/runtime/panic.go @@ -1014,13 +1014,12 @@ func sync_fatal(s string) { // issue #67274, so as to fix longtest builders. // //go:nosplit -//go:noinline func throw(s string) { // Everything throw does should be recursively nosplit so it // can be called even when it's unsafe to grow the stack. systemstack(func() { print("fatal error: ") - printpanicval(s) + printindented(s) // logically printpanicval(s), but avoids convTstring write barrier print("\n") }) @@ -1041,7 +1040,7 @@ func fatal(s string) { // can be called even when it's unsafe to grow the stack. systemstack(func() { print("fatal error: ") - printpanicval(s) + printindented(s) // logically printpanicval(s), but avoids convTstring write barrier print("\n") }) -- cgit v1.3