win32: use built-in shell for popen, if possible

popen uses the shell to run the command provided.  If BusyBox has
been configured appropriately use the built-in shell for this.

- Currently the only user of popen in busybox-w32 is awk, which
  uses it when piping to or from commands.
- If the command is available as an applet the shell will use it.
  If a different version of the program is required the command
  will need to specify the full path.
- This change means that popen will work even if no shell is
  present on the path.
- Since the binary may have been run as sh.exe or awk.exe it's
  necessary to use the magic --busybox option.

1 files changed, 12 insertions, 2 deletions

diff --git a/win32/popen.c b/win32/popen.c
index 6b8e52ca9..59f5ca9f0 100644
--- a/win32/popen.c
+++ b/win32/popen.c
@@ -1,5 +1,6 @@
 #include <fcntl.h>
 #include "libbb.h"
+#include "NUM_APPLETS.h"
 
 typedef struct {
         PROCESS_INFORMATION piProcInfo;
@@ -90,13 +91,22 @@ FILE *mingw_popen(const char *cmd, const char *mode)
                 }
         }
 
-        len = strlen(cmd) + 10 + count;
+        len = strlen(bb_busybox_exec_path) + strlen(cmd) + 32 + count;
         if ( (cmd_buff=malloc(len)) == NULL ) {
                 return NULL;
         }
 
+#if (ENABLE_FEATURE_PREFER_APPLETS || ENABLE_FEATURE_SH_STANDALONE) && \
+                NUM_APPLETS > 1
+        if (find_applet_by_name("sh") >= 0) {
+                strcpy(cmd_buff, bb_busybox_exec_path);
+                strcat(cmd_buff, " --busybox sh -c \"");
+        }
+        else
+#endif
+                strcpy(cmd_buff, "sh -c \"");
+
         /* escape double quotes */
-        strcpy(cmd_buff, "sh -c \"");
         for ( s=cmd,t=cmd_buff+strlen(cmd_buff); *s; ++s ) {
                 if ( *s == '"' ) {
                         *t++ = '\\';