libgo/mklinknames.awk

   1 # Copyright 2020 The Go Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style
   3 # license that can be found in the LICENSE file.
   4
   5 # This AWK script reads a Go file with special //extern-sysinfo
   6 # comments annotating functions which should be linked to libc
   7 # functions. It generates a Go file containing the appropriate
   8 # //go:linkname directives.
   9 #
  10 # For each annotated function, the script searches gen-sysinfo.go
  11 # to see if a different assembly name is known for the function.
  12 # For example, on NetBSD, the timegm symbol is renamed to
  13 # __timegm50 by an __asm__ annotation on its declaration in time.h.
  14
  15 BEGIN {
  16     print "// Code generated by mklinknames.awk. DO NOT EDIT."
  17     print ""
  18     print "package", package
  19     print ""
  20     print "import _ \"unsafe\""
  21     print ""
  22 }
  23
  24 /^\/\/extern-sysinfo/ {
  25     cfnname = $2
  26     getline
  27     if ($1 != "func") {
  28         printf("mklinknames.awk: error: %s:%d: unattached extern-sysinfo directive\n", FILENAME, FNR) | "cat 1>&2"
  29         exit 1
  30     }
  31     split($2, a, "(")
  32     gofnname = a[1]
  33     def = sprintf("grep '^func _%s[ (]' gen-sysinfo.go", cfnname)
  34     # def looks like one of the following:
  35     #     func _timegm (*_tm) int64 __asm__("__timegm50")
  36     #     func _timegm (*_tm) int64 __asm__("*__timegm50")
  37     # The goal is to extract "__timegm50".
  38     if ((def | getline fndef) > 0 && match(fndef, "__asm__\\(\"\\*?")) {
  39         asmname = substr(fndef, RSTART + RLENGTH)
  40         asmname = substr(asmname, 0, length(asmname) - 2)
  41         printf("//go:linkname %s %s\n", gofnname, asmname)
  42     } else {
  43         # Assume the asm name is the same as the declared C name.
  44         printf("//go:linkname %s %s\n", gofnname, cfnname)
  45     }
  46 }