re PR go/86331 (the gccgo's "go" tool looks like failing to invoke any sub go command)

	PR go/86331
    os: check return value as well as error from waitid

    https://gcc.gnu.org/PR86331 indicates that if a signal handler runs it
    is possible for syscall.Syscall6 to return a non-zero errno value even
    if no error occurs. That is a problem in general, but this fix will
    let us work around the general problem for the specific case of
    calling waitid.

    Reviewed-on: https://go-review.googlesource.com/121595

From-SVN: r262313

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 237c46d9a66fc5bcefac01c273367c430e259c86..e65c0bc574b172668969a8c5835b231c5f4083b9 100644 (file)
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-e1fcce0aec27b1f50ac0e736f39f4c806c2a5baa
+94738979a3422e845acf358a766aabf8b9275d43
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

diff --git a/libgo/go/os/wait_waitid.go b/libgo/go/os/wait_waitid.go
index 5a62b27f191f22c98634c30fd0d09919dc65fa44..a6284aad98a5e7d8fd977913888c2838fa088afb 100644 (file)
--- a/libgo/go/os/wait_waitid.go
+++ b/libgo/go/os/wait_waitid.go
@@ -28,9 +28,12 @@ func (p *Process) blockUntilWaitable() (bool, error) {
        // We don't care about the values it returns.
        var siginfo [16]uint64
        psig := &siginfo[0]
-       _, _, e := syscall.Syscall6(syscall.SYS_WAITID, _P_PID, uintptr(p.Pid), uintptr(unsafe.Pointer(psig)), syscall.WEXITED|syscall.WNOWAIT, 0, 0)
+       r, _, e := syscall.Syscall6(syscall.SYS_WAITID, _P_PID, uintptr(p.Pid), uintptr(unsafe.Pointer(psig)), syscall.WEXITED|syscall.WNOWAIT, 0, 0)
        runtime.KeepAlive(p)
-       if e != 0 {
+       // Check r as well as e because syscall.Syscall6 currently
+       // just returns errno, and the SIGCHLD signal handler may
+       // change errno. See https://gcc.gnu.org/PR86331.
+       if r != 0 && e != 0 {
                // waitid has been available since Linux 2.6.9, but
                // reportedly is not available in Ubuntu on Windows.
                // See issue 16610.