ash: Unix-style paths, shell builtins and applets

Some shell builtins also exist as applets:  echo, printf, pwd and
test, for example.  If such an applet is referenced using a Unix-
style path, e.g. /usr/bin/echo, the applet should be run rather
than the builtin.  Instead the current code says:

   sh: /usr/bin/echo: file not found

Rearrange the tests in shellexec() so the correct behaviour occurs.

Actually, the error message was also incorrect due to a separate
bug.  Commit d71cb67ff (win32: revert special treatment of Unix-style
absolute paths) failed to allocate space on the stack so that the
command passed to tryexec() could have an extension added if
required.

1 files changed, 6 insertions, 3 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 913f0ce22..521ab22af 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -9088,6 +9088,7 @@ static void shellexec(char *prog, char **argv, const char *path, int idx)
          || (applet_no = find_applet_by_name(prog)) >= 0
 #endif
         ) {
+                prog = stack_add_ext_space(prog);
                 tryexec(IF_FEATURE_SH_STANDALONE(applet_no,) prog, argv, envp);
                 if (applet_no >= 0) {
                         /* We tried execing ourself, but it didn't work.
@@ -9098,7 +9099,7 @@ static void shellexec(char *prog, char **argv, const char *path, int idx)
                 }
                 e = errno;
 #if ENABLE_PLATFORM_MINGW32
-                if (unix_path(prog) && !find_builtin(bb_basename(prog))) {
+                if (unix_path(prog)) {
 # if ENABLE_FEATURE_SH_STANDALONE
                         const char *name = bb_basename(prog);
                         if ((applet_no = find_applet_by_name(name)) >= 0) {
@@ -9106,8 +9107,10 @@ static void shellexec(char *prog, char **argv, const char *path, int idx)
                                 e = errno;
                         }
 # endif
-                        argv[0] = (char *)bb_basename(prog);
-                        goto try_PATH;
+                        if (!find_builtin(bb_basename(prog))) {
+                                argv[0] = (char *)bb_basename(prog);
+                                goto try_PATH;
+                        }
                 }
 #endif
         } else {