cmd/cgo: newline replacement in composite literals generates invalid code

[flga]

Go version

go1.22.1 linux/amd64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/fl/.cache/go-build'
GOENV='/home/fl/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/fl/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/fl/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/fl/workspace/tools/go/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/fl/workspace/tools/go/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.22.1'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='zig cc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='. -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3518409302=/tmp/go-build -gno-record-gcc-switches'

What did you do?

reproduction in godbolt since the playground does not allow cgo

What did you see happen?

./example.go:8:23: syntax error: unexpected semicolon, expected expression
./example.go:13:26: syntax error: unexpected semicolon, expected expression

What did you expect to see?

Parsing fails because semicolons are incorrectly inserted in the generated code:

func() { _cgoBase0 := /*line :8:10*/&_Ctype_Foo /*line :8:16*/{	a:	1,;	ptr:	nil,}; _cgo0 := _cgoBase0; _cgoCheckPointer(_cgoBase0, 0 == 0); /*line :12:4*/_Cfunc_repro(_cgo0); }()
func() { _cgoBase0 := /*line :13:10*/&_Ctype_Foo /*line :13:16*/{	a:	1,;	ptr:	nil,}; _cgo0 := _cgoBase0; _cgoCheckPointer(_cgoBase0, 0 == 0); /*line :17:4*/_Cfunc_repro(_cgo0); }()

This is because gofmtLineReplacer does not account for consecutive newlines.

While the reproduction is clearly non-problematic, I found the issue in a much more involved construction (VkGraphicsPipelineCreateInfo) in which the freedom to insert newlines and comments is incredibly beneficial.

Furthermore, it appears that perhaps the replacing is too heavy handed in general since it also applies to string literals.

Related: #29748, #31017, #29781

[gopherbot]

Change https://go.dev/cl/586676 mentions this issue: cmd/cgo: accept multiple newlines when avoiding semicolons