cmd/compile: does not check go:writebarrierrec for print functions #34014
Comments
ianlancetaylor
added
the
NeedsInvestigation
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Thanks for this report @ianlancetaylor! I think this issue might show a symptom that With degree 1This is similar to manually adding diff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go
index 6a8b5b7ace..46f4b27f3f 100644
--- a/src/runtime/signal_unix.go
+++ b/src/runtime/signal_unix.go
@@ -229,6 +229,20 @@ func clearSignalHandlers() {
}
}
+//go:nowritebarrierrec
+func f1(x *[]byte, y *[]byte) {
+ foo(x, y)
+}
+
+func f2() {
+ var x, y []byte
+ foo(&x, &y)
+}
+
+func foo(x *[]byte, y *[]byte) {
+ *x = *y
+}
+and on running $ GO111MODULE=off go get .
# runtime
./signal_unix.go:234:8: write barrier prohibited
./signal_unix.go:234:8: write barrier prohibited by caller; f1With degree 2 of connection, inlining enableddiff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go
index 6a8b5b7ace..4aaf4cef87 100644
--- a/src/runtime/signal_unix.go
+++ b/src/runtime/signal_unix.go
@@ -229,6 +229,21 @@ func clearSignalHandlers() {
}
}
+//go:nowritebarrierrec
+func f1(x *[]byte, y *[]byte) []byte {
+ return f2()
+}
+
+func f2() []byte {
+ var x, y []byte
+ return foo(&x, &y)
+}
+
+func foo(x *[]byte, y *[]byte) []byte{
+ *x = *y
+ return *x
+}
+when run doesn't print any error. GO111MODULE=off go get .With degree 2 and disabled inliningdiff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go
index 6a8b5b7ace..4aaf4cef87 100644
--- a/src/runtime/signal_unix.go
+++ b/src/runtime/signal_unix.go
@@ -229,6 +229,21 @@ func clearSignalHandlers() {
}
}
+//go:nowritebarrierrec
+func f1(x *[]byte, y *[]byte) []byte {
+ return f2()
+}
+
+func f2() []byte {
+ var x, y []byte
+ return foo(&x, &y)
+}
+
+func foo(x *[]byte, y *[]byte) []byte{
+ *x = *y
+ return *x
+}
+$ GO111MODULE=off go get -gcflags='-l' .
# runtime
./signal_unix.go:243:8: write barrier prohibited by caller; foo
/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/runtime/signal_unix.go:239:15: called by f2
/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/runtime/signal_unix.go:234:14: called by f1Please re-attempt your experiment with the |
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My apologies, my analysis is totally unrelated to your problem @ianlancetaylor! Regardless of if I use diff --git a/src/runtime/print.go b/src/runtime/print.go
index e605eb34cb..29ea1a864b 100644
--- a/src/runtime/print.go
+++ b/src/runtime/print.go
@@ -238,7 +238,10 @@ func printpointer(p unsafe.Pointer) {
printhex(uint64(uintptr(p)))
}
+var z string
+
func printstring(s string) {
+ z = s
gwrite(bytes(s))
}Unless I also manually set |
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@odeke-em, just to close the loop on your examples, your "With degree 2 of connection, inlining enabled" example doesn't fail because there's actually no write barrier under |
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Got it, thank you @aclements! |
gopherbot
added
the
compiler/runtime
The runtime function
sighandleris markedgo:nowritebarrierrec. It callsprintwhich cmd/compile turns into calls toprintstringand friends. However, if I modifyprintstringto force a write barrier, no error is issued when compiling the runtime package. If I then markprintstringasgo:nowritebarrierrec, I do get an error. My conclusion from this is that cmd/compile does not applygo:nowritebarrierrecto the calls generated by calling theprintfunction.I believe this is because in
(*nowritebarrierrecChecker).checktheprintstringfunctions are never added to thesymToFuncmap.CC @aclements
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