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[dev.typeparams] cmd/compile: record writer's stack at export data sync points

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This CL extends the unified export data format's existing sync
mechanism to save writer stacks, controlled by the -d=syncframes debug
flag. This allows readers to provide more details when reporting
desync errors, which should simplify development of the data format
and the various reader/writer implementations.

For example, CL 328051 updated reader and writer, but missed making a
similar change to the linker (fix in CL 328054). Re-reviewing the CL
in isolation after the failure, it was not immediately obvious what
was going wrong. But the pair of stack traces below identifies exactly
what happened: it should have updated linker.relocFuncExt to write out
the new sync marker too.

```
data sync error: package "internal/abi", section 6, index 4, offset 536

found UseReloc, written at:
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/encoder.go:221: (*encoder).reloc +0x44
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/linker.go:214: (*linker).relocFuncExt +0x580
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/linker.go:233: (*linker).relocTypeExt +0x234
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/linker.go:161: (*linker).relocObj +0x2198
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/linker.go:64: (*linker).relocIdx +0x196

expected ImplicitTypes, reading at:
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/reader.go:796: (*reader).implicitTypes +0x36
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/reader.go:810: (*reader).addBody +0x81
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/reader.go:727: (*reader).funcExt +0x542
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/reader.go:651: (*reader).method +0x324
	/home/mdempsky/wd/go/src/cmd/compile/internal/noder/reader.go:557: (*pkgReader).objIdx +0x2704
```

Change-Id: I911193edd2a965f81b7459f15fb613a773584685
Reviewed-on: https://go-review.googlesource.com/c/go/+/328909
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Matthew Dempsky 2021-06-17 01:12:23 -07:00
parent 78aa251ace
commit 54fe57bc22
8 changed files with 219 additions and 46 deletions
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33
src/cmd/compile/internal/noder/sync.go
View file

@ -6,8 +6,39 @@
package noder
const debug = true
import (
"fmt"
"strings"
)
// enableSync controls whether sync markers are written into unified
// IR's export data format and also whether they're expected when
// reading them back in. They're inessential to the correct
// functioning of unified IR, but are helpful during development to
// detect mistakes.
//
// When sync is enabled, writer stack frames will also be included in
// the export data. Currently, a fixed number of frames are included,
// controlled by -d=syncframes (default 0).
const enableSync = true
// fmtFrames formats a backtrace for reporting reader/writer desyncs.
func fmtFrames(pcs ...uintptr) []string {
res := make([]string, 0, len(pcs))
walkFrames(pcs, func(file string, line int, name string, offset uintptr) {
// Trim package from function name. It's just redundant noise.
name = strings.TrimPrefix(name, "cmd/compile/internal/noder.")
res = append(res, fmt.Sprintf("%s:%v: %s +0x%v", file, line, name, offset))
})
return res
}
type frameVisitor func(file string, line int, name string, offset uintptr)
// syncMarker is an enum type that represents markers that may be
// written to export data to ensure the reader and writer stay
// synchronized.
type syncMarker int
//go:generate stringer -type=syncMarker -trimprefix=sync