tree b7af4d28ff10dcde258c8df993b0462c2403aecc
parent 88a25df9133e9a1fc28a00b08ee30d7e5ab2cdbb
author Nikhil Benesch <nikhil.benesch@gmail.com> 1603737728 +0000
committer Ian Lance Taylor <iant@golang.org> 1603934112 +0000

libgo: handle linking to NetBSD's versioned symbols

On NetBSD, for backwards compatibility, various libc symbols are
renamed to a symbol with a version suffix. For example, this is the
(abbreviated) definition of sigaction:

    int sigaction(...) __asm__ ("__sigaction14")

This poses a challenge for libgo, which attempts to link sigaction by
way of an "//extern" comment:

    //extern sigaction
    func sigaction(...)

This results in a reference to the deprecated compatibility symbol
"sigaction", rather than the desired "__sigaction14" symbol.

This patch introduces a new "//extern-sysinfo" comment to handle this
situation. The new mklinknames.awk script scans a package for these
comments and outputs a "//go:linkname" directive that links the wrapper
to the correct versioned symbol, as determined by parsing the __asm__
annotation on the function's declaration in gen-sysinfo.go.

For now, only the following packages are scanned by mklinknames.awk:

    os
    os/user
    runtime
    syscall

Change-Id: I31b475098aecb9eb0579e8bb5952405e93ac960c
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/265125
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>