ash: optimise running of scripts

The BusyBox shell detects certain cases where forking a command is
unnecessary (last command in a script or subshell, for example) and
calls execve(2) instead.  This doesn't help in the Windows port
because execve(2) is implemented by creating a process.

There is one case where it is possible to apply this optimisation:
if the command is a script and the script interpreter is an applet.

- Have evalcommand() pass a flag to indicate this situation to
  shellexec().  Also, allocate two spare elements before the start
  of the argv array.

- If the flag is TRUE shellexec() passes the shell's PATH variable
  down to tryexec() so it can perform a test for applet override.

- If tryexec() finds that all the necessary conditions apply it
  can run a script by directly invoking the interpreter's main().

Adds 192-224 bytes.

1 files changed, 1 insertions, 8 deletions

diff --git a/win32/process.c b/win32/process.c
index 097a1d71c..e3ce95ca0 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -53,14 +53,7 @@ pid_t mingw_wait3(pid_t pid, int *status, int options, struct rusage *rusage)
         return -1;
 }
 
-typedef struct {
-        char *path;
-        char *name;
-        char *opts;
-        char buf[100];
-} interp_t;
-
-static int
+int FAST_FUNC
 parse_interpreter(const char *cmd, interp_t *interp)
 {
         char *path, *t;