https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63731
Bug ID: 63731
Summary: Fallback to netgo does not work
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: go
Assignee: ian at airs dot com
Reporter: yohei at jp dot ibm.com
CC: cmang at google dot com
When the DNS resolver with CGO fails for statically linked binaries, it should
fall back to the pure-go DNS resolver, if I understand correctly.
This fallback mechanism does work at least on Linux for x86_64 and ppc64le.
The variable ok in lookupIP in go/net/lookup_unix.go seems always set to true,
so the fallback mechanism would never be called.
Here is an example code to demonstrate the problem.
$ gccgo -v
Using built-in specs.
COLLECT_GCC=gccgo
COLLECT_LTO_WRAPPER=/usr/local/gccgo-216834/libexec/gcc/x86_64-unknown-linux-gnu/5.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../src/configure --enable-threads=posix --enable-shared
--enable-__cxa_atexit --enable-languages=c,c++,go --enable-secureplt
--enable-checking=yes --with-long-double-128 --enable-decimal-float
--disable-bootstrap --disable-alsa --disable-multilib
--prefix=/usr/local/gccgo-216834
Thread model: posix
gcc version 5.0.0 20141029 (experimental) (GCC)
$ cat lookup.go
package main
import (
"fmt"
"net"
)
func main() {
addrs, err := net.LookupHost("gcc.gnu.org")
if err != nil {
fmt.Println(err)
} else {
for i := 0; i < len(addrs); i++ {
fmt.Println(addrs[i])
}
}
}
$ gccgo lookup.go
$ ./a.out
209.132.180.131
$ gccgo -static lookup.go
/usr/local/gccgo-216834/lib/gcc/x86_64-unknown-linux-gnu/5.0.0/../../../../lib64/libgo.a(net.o):
In function `net.cgoLookupPort':
/home/yohei/gccgo.216834/bld/x86_64-unknown-linux-gnu/libgo/../../../src/libgo/go/net/cgo_unix.go:83:
warning: Using 'getaddrinfo' in statically linked applications requires at
runtime the shared libraries from the glibc version used for linking
$ ./a.out
lookup gcc.gnu.org: Name or service not known
$ LD_LIBRARY_PATH=/lib/x86_64-linux-gnu ./a.out
209.132.180.131
