cygwin: use spawnvp for run and sh.

We revive the dead _wspawnvp code that was used on MinGW, a
platform that has not been supported for years, adapting it
for Cygwin.

* configure: Correct the _wspawnlp test; it should have been
testing for _wspawnvp function, which is what is is actually
used by the matching code. Moreover, the broken test was
calling _wspawnlp with _wspawnvp style arguments. Anyway, this
is moot because we will never detect this function in the
foreseeable future.  More importantly, adding a test for
spawnvp, which exists on Cygwin.

* stream.c: Include the <process.h> header if HAVE_WSPAWN or
HAVE_SPAWN. This was missing before; how did the _wspawnvp
call ever compile?
(w_spawnvp): New static function.
(run): spawn version now calls either _wspawwnvp or w_spawnvp
if that is not available. We test for HAVE_WSPAWN or
HAVE_SPAWN first, before HAVE_FORK_STUFF, so that we use the
spawn function preferentially. On Cygwin, we have the fork
stuff.

1 files changed, 21 insertions, 2 deletions

diff --git a/configure b/configure
index 4198718d..18390a21 100755
--- a/configure
+++ b/configure
@@ -2506,7 +2506,7 @@ else
   printf "no\n"
 fi
 
-printf "Checking for _wspawnlp ... "
+printf "Checking for _wspawnvp ... "
 
 cat > conftest.c <<!
 #include "config.h"
@@ -2516,7 +2516,7 @@ cat > conftest.c <<!
 int main(int argc, char **argv)
 {
   wchar_t *wargv[] = { L"foo", L"bar", 0 };
-  int r = _wspawnlp(_P_WAIT, L"foo", wargv);
+  int r = _wspawnvp(_P_WAIT, L"foo", wargv);
   return 0;
 }
 !
@@ -2527,6 +2527,25 @@ else
   printf "no\n"
 fi
 
+printf "Checking for spawnvp ... "
+
+cat > conftest.c <<!
+#include "config.h"
+#include <process.h>
+
+int main(int argc, char **argv)
+{
+  int r = spawnvp(_P_WAIT, "foo", argv);
+  return 0;
+}
+!
+if conftest ; then
+  printf "yes\n"
+  printf "#define HAVE_SPAWN 1\n" >> config.h
+else
+  printf "no\n"
+fi
+
 printf "Checking for chsize ... "
 cat > conftest.c <<!
 #include <unistd.h>