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# Copyright 2020 The Go Authors. All rights reserved.
# Use of this source code is governed by a BSD-style
# license that can be found in the LICENSE file.
# This AWK script reads a Go file with special //extern-sysinfo
# comments annotating functions which should be linked to libc
# functions. It generates a Go file containing the appropriate
# //go:linkname directives.
#
# For each annotated function, the script searches gen-sysinfo.go
# to see if a different assembly name is known for the function.
# For example, on NetBSD, the timegm symbol is renamed to
# __timegm50 by an __asm__ annotation on its declaration in time.h.
BEGIN {
print "// Code generated by mklinknames.awk. DO NOT EDIT."
print ""
print "package", package
print ""
print "import _ \"unsafe\""
print ""
}
/^\/\/extern-sysinfo/ {
cfnname = $2
getline
if ($1 != "func") {
printf("mklinknames.awk: error: %s:%d: unattached extern-sysinfo directive\n", FILENAME, FNR) | "cat 1>&2"
exit 1
}
split($2, a, "(")
gofnname = a[1]
def = sprintf("grep '^func _%s[ (]' gen-sysinfo.go", cfnname)
# def looks like one of the following:
# func _timegm (*_tm) int64 __asm__("__timegm50")
# func _timegm (*_tm) int64 __asm__("*__timegm50")
# The goal is to extract "__timegm50".
if ((def | getline fndef) > 0 && match(fndef, "__asm__\\(\"\\*?")) {
asmname = substr(fndef, RSTART + RLENGTH)
asmname = substr(asmname, 0, length(asmname) - 2)
printf("//go:linkname %s %s\n", gofnname, asmname)
} else {
# Assume the asm name is the same as the declared C name.
printf("//go:linkname %s %s\n", gofnname, cfnname)
}
}
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