They look like linker errors. Does it work without -cover?

@Dhananjay92,

Does it work without -cover?

See https://build.golang.org.

The cmd/cover package just generates annotated source files. So just guessing that some modification to runtime package during Go 1.8 development cycle breaks the existing plumbing work for shared libraries.

Okay, root cause is that the compiler directives in src/runtime/os3_solaris.go disappear during coverage instrumentation.

Confirmed with,

$ go tool cover -mode=count runtime/os3_solaris.go
# .. notice that the compiler directives are present ...

$ ../pkg/tool/linux_amd64/cover -mode=count runtime/os3_solaris.go
# ... notice absence of compiler directives ...

This is happening because of my own change: golang.org/cl/30161. Coverage instrumentation removes all comments that are not present as nodes in the AST; because they were interfering with inserted code.

Parser doesn't keep these compiler directives as nodes in AST, but instead as CommentGroup in ast.File.Comments with all other comments. The fix that solves both this and #17315 would be to either keep all compiler directive into AST as nodes, Or handle such un-attached compiler directives explicitly like cover does for // +build tags.

Working on the fix.

PS: The issue will go away with JayNakrani@4a16ac8 because doing that makes parser keep those comments in AST. Parser only keeps comments into the tree that can potentially be document-comments

I think Ian had told me some time earlier that the compiler directives are associated with something (a function or variable, etc). If that's the case, fix would be JayNakrani@4a16ac8.

Let me confirm with him again.

@Dhananjay92,

Thanks for the investigation. As you mentioned above, a few packages that import runtime symbols by using //go:cgo_import_dynamic or //go:linkname annotation, for example vendor/golang_org/x/net/lif, golang.org/x/net/lif or golang.org/x/sys, surely crash when using cmd/cover.

/CC @ianlancetaylor

CL https://golang.org/cl/34563 mentions this issue.

golang.org/cl/34563 takes care of such compiler directives that aren't attached to any node in the AST.

My another attempt to let printer print such compiler directives, failed. Because ast/printer can either print from ast.File.Comment or from nodes in the tree, but not from both.