runtime/race: eliminate dependency on libc

[dvyukov]

Race runtime currently depends on libc:

with CGO_ENABLED=0:
runtime/race(.text): __libc_malloc: not defined
runtime/race(.text): getuid: not defined
runtime/race(.text): pthread_self: not defined
...

This has several negative effects:

• don't work with CGO_ENABLED=0
• there is circular dependency between runtime/race and cmd/cgo
• cross-compilation is close to impossible
• external linkage is required

If we eliminate all libc dependencies from race runtime, all these problems go away.

[dvyukov]

related to #6508

[dlsniper]

Hi, I wish to add that currently doing go test -race ./... inside a go:1.5.3-alpine container, with CGO disabled, will fail due to this.

PROJECT_DIR="${PWD}" #assume we are in $GOPATH/src/github.com/dlsniper/demo on the computer
CONTAINER_PROJECT_DIR="/go/src/github.com/dlsniper/demo"
CONTAINER_PROJECT_GOPATH="${CONTAINER_PROJECT_DIR}/vendor:/go"

docker run --rm \
        --net="host" \
        -v ${PROJECT_DIR}:${CONTAINER_PROJECT_DIR} \
        -e CI=true \
        -e GODEBUG=netdns=go \
        -e CGO_ENABLED=0 \
        -e GOPATH=${CONTAINER_PROJECT_GOPATH} \
        -w "${CONTAINER_PROJECT_DIR}" \
        golang:1.5.3-alpine \
        go test -v -race ./...

Output:

# testmain
runtime/race(.text): __libc_malloc: not defined
runtime/race(.text): getuid: not defined
runtime/race(.text): pthread_self: not defined
runtime/race(.text): madvise: not defined
runtime/race(.text): madvise: not defined
runtime/race(.text): madvise: not defined
runtime/race(.text): sleep: not defined
runtime/race(.text): usleep: not defined
runtime/race(.text): abort: not defined
runtime/race(.text): isatty: not defined
runtime/race(.text): __libc_free: not defined
runtime/race(.text): getrlimit: not defined
runtime/race(.text): pipe: not defined
runtime/race(.text): __libc_stack_end: not defined
runtime/race(.text): getrlimit: not defined
runtime/race(.text): setrlimit: not defined
runtime/race(.text): setrlimit: not defined
runtime/race(.text): setrlimit: not defined
runtime/race(.text): exit: not defined
runtime/race(.text.unlikely): __errno_location: not defined
runtime/race(.text): undefined: __libc_malloc
/usr/local/go/pkg/tool/linux_amd64/link: too many errors

Not sure if I should open a separate issue or this comment is enough, please advise. Also the example is not meant to work as it currently points to an non-existing repository but I can make it work if needed.

Thank you.

[dvyukov]

Please file a separate issue. Race detector must work regardless of dependency on libc. Looks like some issue with linker. Does it work with 1.6? I guess it won't be fixed in 1.5 at this point.

[gopherbot]

CL https://golang.org/cl/41678 mentions this issue.