cmd/cgo: fails to generate certain types with Go 1.14

[tklauser]

What version of Go are you using (go version)?

$ go version
go version go1.14 linux/amd64

Does this issue reproduce with the latest release?

Yes, it also reproduces with tip. However, it doesn't reproduce with go1.13.8

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/tklauser/.cache/go-build"
GOENV="/home/tklauser/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/tklauser/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/tklauser/src/go/src/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build562307077=/tmp/go-build -gno-record-gcc-switches"

What did you do?

$ cat repro.go
package unix

/*
#include <time.h>
#include <linux/errqueue.h>
*/
import "C"

type Timespec C.struct_timespec

type ScmTimestamping C.struct_scm_timestamping

$ go1.14 tool cgo -godefs repro.go
// Code generated by cmd/cgo -godefs; DO NOT EDIT.
// cgo -godefs cgo-fail-go1.14.go

package unix

type Timespec struct {
	Sec	int64
	Nsec	int64
}

type ScmTimestamping struct {
	Ts [3]_Ctype_struct_timespec
}

For some reason cgo is unable to resolve __Ctype_struct_timespec to Timespec in Go 1.14, while it does with Go 1.13 (see below). This looks like a regression to me.

Found while trying to update the code generation in golang.org/x/sys/unix to use Go 1.14.

What did you expect to see?

$ go1.13.8 tool cgo -godefs repro.go
// Code generated by cmd/cgo -godefs; DO NOT EDIT.
// cgo -godefs cgo-fail-go1.14.go

package unix

type Timespec struct {
	Sec	int64
	Nsec	int64
}

type ScmTimestamping struct {
	Ts [3]Timespec
}

What did you see instead?

See output of go1.14 tool cgo -godefs repro.go above.

[tklauser]

/cc @ianlancetaylor

[tklauser]

@gopherbot please consider this for backport to 1.14, it's a regression.

[gopherbot]

Backport issue(s) opened: #37622 (for 1.14).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://golang.org/wiki/MinorReleases.

[tklauser]

Found while trying to update the code generation in golang.org/x/sys/unix to use Go 1.14.

FWIW, this was the resulting diff when I tried to regenerate the files in x/sys/unix:

diff --git a/unix/linux/Dockerfile b/unix/linux/Dockerfile
index 0e4a930959aa..e93b354c56ab 100644
--- a/unix/linux/Dockerfile
+++ b/unix/linux/Dockerfile
@@ -18,9 +18,9 @@ RUN git clone --branch v5.5 --depth 1 https://kernel.googlesource.com/pub/scm/li
 RUN git clone --branch release/2.31/master --depth 1 git://sourceware.org/git/glibc.git
 
 # Get Go
-ENV GOLANG_VERSION 1.13.7
+ENV GOLANG_VERSION 1.14
 ENV GOLANG_DOWNLOAD_URL https://golang.org/dl/go$GOLANG_VERSION.linux-amd64.tar.gz
-ENV GOLANG_DOWNLOAD_SHA256 b3dd4bd781a0271b33168e627f7f43886b4c5d1c794a4015abf34e99c6526ca3
+ENV GOLANG_DOWNLOAD_SHA256 08df79b46b0adf498ea9f320a0f23d6ec59e9003660b4c9c1ce8e5e2c6f823ca
 
 RUN curl -fsSL "$GOLANG_DOWNLOAD_URL" -o golang.tar.gz \
     && echo "$GOLANG_DOWNLOAD_SHA256  golang.tar.gz" | sha256sum -c - \
diff --git a/unix/ztypes_linux.go b/unix/ztypes_linux.go
index 6c81e7515c87..ee0f94a1f393 100644
--- a/unix/ztypes_linux.go
+++ b/unix/ztypes_linux.go
@@ -1757,7 +1757,7 @@ const (
 )
 
 type ScmTimestamping struct {
-       Ts [3]Timespec
+       Ts [3]_Ctype_struct_timespec
 }
 
 const (
diff --git a/unix/ztypes_linux_s390x.go b/unix/ztypes_linux_s390x.go
index a111387b3ac5..44d756de41c7 100644
--- a/unix/ztypes_linux_s390x.go
+++ b/unix/ztypes_linux_s390x.go
@@ -165,12 +165,12 @@ const (
 )
 
 type PtraceRegs struct {
-       Psw                      PtracePsw
+       Psw                      _Ctype_struct__user_psw_struct
        Gprs                     [16]uint64
        Acrs                     [16]uint32
        Orig_gpr2                uint64
-       Fp_regs                  PtraceFpregs
-       Per_info                 PtracePer
+       Fp_regs                  _Ctype_struct__user_fpregs_struct
+       Per_info                 _Ctype_struct__user_per_struct
        Ieee_instruction_pointer uint64
 }

[ianlancetaylor]

See also #37479. I guess we need to figure this out.

[bcmills]

Possibly a side-effect of CL 181857?

[tklauser]

Possibly a side-effect of CL 181857?

Yes, CL 181857 seems to have introduced this regression. If I revert the CL, the generated code is as expected.

@ianlancetaylor also traced down #37479 to the same CL.

[gopherbot]

Change https://golang.org/cl/226341 mentions this issue: cmd/cgo, misc/cgo: only cache anonymous struct typedefs with parent name

[gopherbot]

Change https://golang.org/cl/226497 mentions this issue: cmd/cgo, misc/cgo: only cache anonymous struct typedefs with parent name

[gopherbot]

Change https://golang.org/cl/226577 mentions this issue: unix: update Dockerfile to Linux 5.6, and Go 1.13.9