Fix bugs:

457466: popenx() argument mangling hangs python
 226766: popen('python -c"...."') tends to hang

Fixes argument quoting in w9xpopen.exe for Windows 9x.  w9xpopen.exe
also never attempts to display a MessageBox when not executed
interactively.

Added test_popen() test.  This test currently just executes
"python -c ..." as a child process, and checks that the expected
arguments were all recieved correctly by the child process.  This
test succeeds for me on Win9x, win2k and Linux, and I hope it does
for other popen supported platforms too :)

Lib/test/output/test_popen

@@ -0,0 +1,3 @@
+test_popen
+Test popen:
+popen seemed to process the command-line correctly

Lib/test/test_popen.py

@@ -0,0 +1,36 @@
+#! /usr/bin/env python
+"""Basic tests for os.popen()
+
+  Particularly useful for platforms that fake popen.
+"""
+
+import os
+import sys
+from test_support import TestSkipped
+from os import popen
+
+# Test that command-lines get down as we expect.
+# To do this we execute:
+#    python -c "import sys;print sys.argv" {rest_of_commandline}
+# This results in Python being spawned and printing the sys.argv list.
+# We can then eval() the result of this, and see what each argv was.
+def _do_test_commandline(cmdline, expected):
+    cmd = 'python -c "import sys;print sys.argv" %s' % (cmdline,)
+    data = popen(cmd).read()
+    got = eval(data)[1:] # strip off argv[0]
+    if got != expected:
+        print "Error in popen commandline handling."
+        print " executed '%s', expected '%r', but got '%r'" \
+                                                    % (cmdline, expected, got)
+
+def _test_commandline():
+    _do_test_commandline("foo bar", ["foo", "bar"])
+    _do_test_commandline('foo "spam and eggs" "silly walk"', ["foo", "spam and eggs", "silly walk"])
+    _do_test_commandline('foo "a \\"quoted\\" arg" bar', ["foo", 'a "quoted" arg', "bar"])
+    print "popen seemed to process the command-line correctly"
+
+def main():
+    print "Test popen:"
+    _test_commandline()
+
+main()

Modules/posixmodule.c

@@ -3285,9 +3285,15 @@ _PyPopenCreateProcess(char *cmdstring,
 
 			s2 = (char *)_alloca(x);
 			ZeroMemory(s2, x);
+			/* To maintain correct argument passing semantics,
+			   we pass the command-line as it stands, and allow
+			   quoting to be applied.  w9xpopen.exe will then
+			   use its argv vector, and re-quote the necessary
+			   args for the ultimate child process.
+			*/
 			PyOS_snprintf(
 				s2, x,
-				"%s \"%s%s%s\"",
+				"\"%s\" %s%s%s",
 				modulepath,
 				s1,
 				s3,

PC/w9xpopen.c

@@ -16,9 +16,10 @@
 
 #define WINDOWS_LEAN_AND_MEAN
 #include <windows.h>
+#include <stdio.h>
 
 const char *usage =
-"This program is used by Python's os.pipe function to\n"
+"This program is used by Python's os.popen function to\n"
 "to work around a limitation in Windows 95/98.  It is\n"
 "not designed to be used as stand-alone program.";
 
@@ -28,11 +29,56 @@ int main(int argc, char *argv[])
     STARTUPINFO si;
     PROCESS_INFORMATION pi;
     DWORD exit_code=0;
+    int cmdlen = 0;
+    int i;
+    char *cmdline, *cmdlinefill;
 
-    if (argc != 2) {
-        MessageBox(NULL, usage, argv[0], MB_OK);
+    if (argc < 2) {
+        if (GetFileType(GetStdHandle(STD_INPUT_HANDLE))==FILE_TYPE_CHAR)
+            /* Attached to a console, and therefore not executed by Python
+               Display a message box for the inquisitive user
+            */
+            MessageBox(NULL, usage, argv[0], MB_OK);
+        else {
+            /* Eeek - executed by Python, but args are screwed!
+               Write an error message to stdout so there is at
+               least some clue for the end user when it appears
+               in their output.
+               A message box would be hidden and blocks the app.
+             */
+            fprintf(stdout, "Internal popen error - no args specified\n%s\n", usage);
+        }
         return 1;
     }
+    /* Build up the command-line from the args.
+       Args with a space are quoted, existing quotes are escaped.
+       To keep things simple calculating the buffer size, we assume
+       every character is a quote - ie, we allocate double what we need
+       in the worst case.  As this is only double the command line passed
+       to us, there is a good chance this is reasonably small, so the total 
+       allocation will almost always be < 512 bytes.
+    */
+    for (i=1;i<argc;i++)
+        cmdlen += strlen(argv[i])*2 + 3; /* one space, maybe 2 quotes */
+    cmdline = cmdlinefill = (char *)malloc(cmdlen+1);
+    if (cmdline == NULL)
+        return -1;
+    for (i=1;i<argc;i++) {
+        const char *arglook;
+        int bQuote = strchr(argv[i], ' ') != NULL;
+        if (bQuote)
+            *cmdlinefill++ = '"';
+        /* escape quotes */
+        for (arglook=argv[i];*arglook;arglook++) {
+            if (*arglook=='"')
+                *cmdlinefill++ = '\\';
+            *cmdlinefill++ = *arglook;
+        }
+        if (bQuote)
+            *cmdlinefill++ = '"';
+        *cmdlinefill++ = ' ';
+    }
+    *cmdlinefill = '\0';
 
     /* Make child process use this app's standard files. */
     ZeroMemory(&si, sizeof si);
@@ -43,13 +89,15 @@ int main(int argc, char *argv[])
     si.hStdError = GetStdHandle(STD_ERROR_HANDLE);
 
     bRet = CreateProcess(
-        NULL, argv[1],
+        NULL, cmdline,
         NULL, NULL,
         TRUE, 0,
         NULL, NULL,
         &si, &pi
         );
 
+    free(cmdline);
+
     if (bRet) {
         if (WaitForSingleObject(pi.hProcess, INFINITE) != WAIT_FAILED) {
 	    GetExitCodeProcess(pi.hProcess, &exit_code);