win32: use built-in applets for non-existent binaries with Unix-style paths

Shell scripts moved from Unix may contain hard-coded paths to
binaries such as /bin/sh.  A recent commit made it possible to
execute such binaries reliably, but that does require them to be
installed.  As an alternative solution:  if a binary with a
standard Unix path prefix can't be found but is available as a
built-in applet, run the applet.

Add the function unix_path() to detect paths starting with /bin,
/usr/bin, /sbin or /usr/sbin.

Use this function in:

- the 'which' applet
- shellexec(), describe_command() and find_command() in ash
- mingw_spawn_1()

See GitHub issue #195.

1 files changed, 13 insertions, 0 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index e63ffa0ac..4ffc49e9a 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -1818,6 +1818,19 @@ void *get_proc_addr(const char *dll, const char *function,
         return proc->pfunction;
 }
 
+#if ENABLE_FEATURE_SH_STANDALONE || ENABLE_FEATURE_PREFER_APPLETS
+int unix_path(const char *path)
+{
+        int i;
+        char *p = strdup(path);
+
+#define UNIX_PATHS "/bin\0/usr/bin\0/sbin\0/usr/sbin\0"
+        i = index_in_strings(UNIX_PATHS, dirname(p));
+        free(p);
+        return i >= 0;
+}
+#endif
+
 /* Return true if file is referenced using a path.  This means a path
  * look-up isn't required. */
 int has_path(const char *file)