system: stop using popen if we have fork.

On all the platforms on which TXR is regularly built, there is
fork, including the Windows port via Cygwin. We therefore
don't have to be using popen for the open-command function.
The handling the stream redirection will be more efficient if
we implement open-command in terms of open-process, and the
special mode string extensions for redirection like ">21"
will work, too.

* stream.c (fds_subst, fds_swizzle): Define these functions
only for !HAVE_FORK_STUFF platforms.
(open_command): popen-based implementation moved down into a
section of code for !HAVE_FORK_STUFF platforms. A separate
implementation is written for HAVE_FORK_STUFF platforms
which passes the command to an appropriate Windows native
or POSIX interpreter.

* utf8.c (w_popen): Nothing but open-command calls this
function, so we don't need it on HAVE_FORK_STUFF platforms.
Wrap with #if.

* utf8.h (w_popen): wrap with #if.

3 files changed, 62 insertions, 35 deletions

diff --git a/stream.c b/stream.c
index 5a303685..1c61873b 100644
--- a/stream.c
+++ b/stream.c
@@ -4261,6 +4261,7 @@ static int fds_getfd(val stream, val self)
   return fd_sub;
 }
 
+#if !HAVE_FORK_STUFF
 static int fds_subst(int fd_sub, int fd_std, val self)
 {
   if (fd_sub == fd_std)
@@ -4278,6 +4279,7 @@ static int fds_subst(int fd_sub, int fd_std, val self)
               self, num(errno), errno_to_str(errno), nao);
   }
 }
+#endif
 
 static void fds_subst_nosave(int fd_sub, int fd_std)
 {
@@ -4298,6 +4300,7 @@ static void fds_prepare(struct save_fds *fds, int flags, val self)
     fds->suberr = fds_getfd(std_error, self);
 }
 
+#if !HAVE_FORK_STUFF
 static void fds_swizzle(struct save_fds *fds, int flags, val self)
 {
   if ((flags & FDS_IN) != 0)
@@ -4327,6 +4330,7 @@ static void fds_restore(struct save_fds *fds)
     close(fds->err);
   }
 }
+#endif
 
 static void fds_clobber(struct save_fds *fds, int flags)
 {
@@ -4340,41 +4344,6 @@ static void fds_clobber(struct save_fds *fds, int flags)
     fds_subst_nosave(fds->suberr, STDERR_FILENO);
 }
 
-val open_command(val path, val mode_str)
-{
-  val self = lit("open-command");
-  struct stdio_mode m, m_r = stdio_mode_init_r;
-  val mode = normalize_mode_no_bin(&m, mode_str, m_r);
-  int input = m.read != 0;
-  struct save_fds sfds;
-  FILE *f = 0;
-  int fds_flags = (input ? FDS_IN : FDS_OUT) | FDS_ERR;
-
-  fds_init(&sfds);
-
-  uw_simple_catch_begin;
-
-  fds_prepare(&sfds, fds_flags, self);
-
-  fds_swizzle(&sfds, fds_flags, self);
-
-  f = w_popen(c_str(path), c_str(mode));
-
-  if (!f) {
-    int eno = errno;
-    uw_throwf(errno_to_file_error(eno), lit("~a: error opening pipe ~s: ~d/~s"),
-              self, path, num(eno), errno_to_str(eno), nao);
-  }
-
-  uw_unwind {
-    fds_restore(&sfds);
-  }
-
-  uw_catch_end;
-
-  return set_mode_props(m, make_pipe_stream(f, path));
-}
-
 #if HAVE_FORK_STUFF
 static val open_subprocess(val name, val mode_str, val args, val fun)
 {
@@ -4531,8 +4500,62 @@ val open_process(val name, val mode_str, val args)
 {
   return open_subprocess(name, mode_str, args, nil);
 }
+
+val open_command(val command, val mode_str)
+{
+#ifdef __CYGWIN__
+  uses_or2;
+  const wchar_t *psc = coerce(const wchar_t *, path_sep_chars);
+  val interp = if3(psc[0] == '\\',
+                   or2(getenv_wrap(lit("COMSPEC")),
+                       lit("C:\\WINDOWS\\system32\\cmd.exe")),
+                   lit("/bin/sh"));
+  val opt = if3(psc[0] == '\\', lit("/c"), lit("-c"));
+#else
+  val interp = lit("/bin/sh");
+  val opt = lit("-c");
+#endif
+  return open_process(interp, mode_str, list(opt, command, nao));
+}
+
 #else
 
+val open_command(val path, val mode_str)
+{
+  val self = lit("open-command");
+  struct stdio_mode m, m_r = stdio_mode_init_r;
+  val mode = normalize_mode_no_bin(&m, mode_str, m_r);
+  int input = m.read != 0;
+  struct save_fds sfds;
+  FILE *f = 0;
+  int fds_flags = (input ? FDS_IN : FDS_OUT) | FDS_ERR;
+
+  fds_init(&sfds);
+
+  uw_simple_catch_begin;
+
+  fds_prepare(&sfds, fds_flags, self);
+
+  fds_swizzle(&sfds, fds_flags, self);
+
+  f = w_popen(c_str(path), c_str(mode));
+
+  if (!f) {
+    int eno = errno;
+    uw_throwf(errno_to_file_error(eno), lit("~a: error opening pipe ~s: ~d/~s"),
+              self, path, num(eno), errno_to_str(eno), nao);
+  }
+
+  uw_unwind {
+    fds_restore(&sfds);
+  }
+
+  uw_catch_end;
+
+  return set_mode_props(m, make_pipe_stream(f, path));
+}
+
+
 static void string_extend_count(int count, val out, val tail)
 {
   int i;
diff --git a/utf8.c b/utf8.c
index 0d484f4f..b8650fdd 100644
--- a/utf8.c
+++ b/utf8.c
@@ -374,6 +374,7 @@ FILE *w_fopen(const wchar_t *wname, const wchar_t *wmode)
   return f;
 }
 
+#if !HAVE_FORK_STUFF
 FILE *w_popen(const wchar_t *wcmd, const wchar_t *wmode)
 {
   char *cmd = utf8_dup_to(wcmd);
@@ -383,6 +384,7 @@ FILE *w_popen(const wchar_t *wcmd, const wchar_t *wmode)
   free(mode);
   return f;
 }
+#endif
 
 FILE *w_freopen(const wchar_t *wname, const wchar_t *wmode, FILE *fold)
 {
diff --git a/utf8.h b/utf8.h
index 22287f2d..0ba4e821 100644
--- a/utf8.h
+++ b/utf8.h
@@ -51,7 +51,9 @@ void utf8_decoder_init(utf8_decoder_t *);
 wint_t utf8_decode(utf8_decoder_t *,int (*get)(mem_t *ctx), mem_t *ctx);
 
 FILE *w_fopen(const wchar_t *, const wchar_t *);
+#if !HAVE_FORK_STUFF
 FILE *w_popen(const wchar_t *, const wchar_t *);
+#endif
 FILE *w_freopen(const wchar_t *, const wchar_t *, FILE *);
 FILE *w_fdopen(int, const wchar_t *);
 int w_remove(const wchar_t *);