win32: more efficient tests for executables

file_is_executable() calls access(2) and stat(2); in this case our
WIN32 implementation also calls stat(2).  Avoid this unnecessary
duplication by copying the required test from the WIN32 access(2).

In find_executable() it's possible to avoid calling file_is_executable()
if add_win32_extension() returns TRUE as the latter will already have
verified that the file is executable.

Replace a call to file_is_executable() in the tab completion code
with the equivalent tests, avoiding (up to) two calls to stat(2).

These changes don't affect the size of the binary and should be
faster.

2 files changed, 10 insertions, 4 deletions

diff --git a/libbb/executable.c b/libbb/executable.c
index e20bf89e4..32b37f29d 100644
--- a/libbb/executable.c
+++ b/libbb/executable.c
@@ -15,7 +15,12 @@
 int FAST_FUNC file_is_executable(const char *name)
 {
         struct stat s;
+#if !ENABLE_PLATFORM_MINGW32
         return (!access(name, X_OK) && !stat(name, &s) && S_ISREG(s.st_mode));
+#else
+        /* expand WIN32 implementation of access(2) */
+        return (!stat(name, &s) && S_ISREG(s.st_mode) && (s.st_mode & S_IXUSR));
+#endif
 }
 
 /* search (*PATHp) for an executable file;
@@ -53,12 +58,13 @@ char* FAST_FUNC find_executable(const char *filename, char **PATHp)
 #if ENABLE_PLATFORM_MINGW32
                 {
                         char *w = alloc_system_drive(p);
-                        add_win32_extension(w);
+                        ex = add_win32_extension(w) || file_is_executable(w);
                         free(p);
                         p = w;
                 }
-#endif
+#else
                 ex = file_is_executable(p);
+#endif
                 if (n) *n++ = PATH_SEP;
                 if (ex) {
                         *PATHp = n;
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index e7de32250..f17c9a215 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -958,8 +958,8 @@ static NOINLINE unsigned complete_cmd_dir_file(const char *command, int type)
                                 goto cont; /* hmm, remove in progress? */
 
 # if ENABLE_PLATFORM_MINGW32
-                        if (type == FIND_EXE_ONLY && !S_ISDIR(st.st_mode) &&
-                                        !file_is_executable(found))
+                        if (type == FIND_EXE_ONLY && S_ISREG(st.st_mode) &&
+                                        !(st.st_mode & S_IXUSR))
                                 goto cont;
 # endif