win32: code shrink detection of executables

Add a function, file_is_win32_exe(), to detect if a path refers
to an executable.  It tries adding extensions if necessary.

Use this in a number of places to replace common code of the form

   path = alloc_ext_space(cmd);
   if (add_win32_extension(path) || file_is_executable(path))

Saves 32-48 bytes.

5 files changed, 41 insertions, 28 deletions

diff --git a/debianutils/which.c b/debianutils/which.c
index b2cd4de18..4af6daf4f 100644
--- a/debianutils/which.c
+++ b/debianutils/which.c
@@ -12,9 +12,8 @@
 //config:       which is used to find programs in your PATH and
 //config:       print out their pathnames.
 
-// NOTE: For WIN32 this applet is NOEXEC as alloc_ext_space() and
-//       find_executable() both allocate memory.  And find_executable()
-//       calls alloc_ext_space().
+// NOTE: For WIN32 this applet is NOEXEC as file_is_win32_exe() and
+//       find_executable() both allocate memory.
 
 //applet:IF_PLATFORM_MINGW32(IF_WHICH(APPLET_NOEXEC(which, which, BB_DIR_USR_BIN, BB_SUID_DROP, which)))
 //applet:IF_PLATFORM_POSIX(IF_WHICH(APPLET_NOFORK(which, which, BB_DIR_USR_BIN, BB_SUID_DROP, which)))
@@ -87,9 +86,9 @@ int which_main(int argc UNUSED_PARAM, char **argv)
                         }
 #else
                 if (has_path(*argv)) {
-                        char *path = alloc_ext_space(*argv);
+                        char *path = file_is_win32_exe(*argv);
 
-                        if (add_win32_extension(path) || file_is_executable(path)) {
+                        if (path) {
                                 missing = 0;
                                 puts(bs_to_slash(path));
                         }
@@ -103,11 +102,9 @@ int which_main(int argc UNUSED_PARAM, char **argv)
 # endif
                                 {
                                         argv[0] = (char *)name;
-                                        free(path);
                                         goto try_PATH;
                                 }
                         }
-                        free(path);
 #endif
                 } else {
                         char *path;
diff --git a/include/mingw.h b/include/mingw.h
index e49483307..7e6109f2e 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -559,7 +559,9 @@ void init_codepage(void);
 int has_bat_suffix(const char *p);
 int has_exe_suffix(const char *p);
 int has_exe_suffix_or_dot(const char *name);
+char *alloc_ext_space(const char *path);
 int add_win32_extension(char *p);
+char *file_is_win32_exe(const char *name);
 
 char *bs_to_slash(char *p) FAST_FUNC;
 void slash_to_bs(char *p) FAST_FUNC;
@@ -578,7 +580,6 @@ int unc_root_len(const char *dir);
 int root_len(const char *path);
 const char *get_system_drive(void);
 const char *need_system_drive(const char *path);
-char *alloc_ext_space(const char *path);
 int chdir_system_drive(void);
 char *xabsolute_path(char *path);
 char *get_drive_cwd(const char *path, char *buffer, int size);
diff --git a/libbb/executable.c b/libbb/executable.c
index 770aedc0c..606bec986 100644
--- a/libbb/executable.c
+++ b/libbb/executable.c
@@ -57,10 +57,12 @@ char* FAST_FUNC find_executable(const char *filename, char **PATHp)
                 );
 #if ENABLE_PLATFORM_MINGW32
                 {
-                        char *w = alloc_ext_space(p);
-                        ex = add_win32_extension(w) || file_is_executable(w);
-                        free(p);
-                        p = w;
+                        char *w = file_is_win32_exe(p);
+                        ex = w != NULL;
+                        if (ex) {
+                                free(p);
+                                p = w;
+                        }
                 }
 #else
                 ex = file_is_executable(p);
diff --git a/win32/mingw.c b/win32/mingw.c
index c7eeea088..0a1af6b72 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -2001,6 +2001,15 @@ int has_exe_suffix_or_dot(const char *name)
         return last_char_is(name, '.') || has_win_suffix(name, 0);
 }
 
+/* Copy path to an allocated string long enough to allow a file extension
+ * to be added. */
+char *alloc_ext_space(const char *path)
+{
+        char *s = xmalloc(strlen(path) + 5);
+        strcpy(s, path);
+        return s;
+}
+
 /* Check if path can be made into an executable by adding a suffix.
  * The suffix is added to the end of the argument which must be
  * long enough to allow this.
@@ -2024,6 +2033,22 @@ int add_win32_extension(char *p)
         return FALSE;
 }
 
+/*
+ * Determine if a path represents a WIN32 executable, adding a suffix
+ * if necessary.  Returns an allocated string if it does, NULL if not.
+ */
+char *
+file_is_win32_exe(const char *name)
+{
+        char *path = alloc_ext_space(name);
+
+        if ((add_win32_extension(path) || file_is_executable(path)))
+                return path;
+
+        free(path);
+        return NULL;
+}
+
 char * FAST_FUNC bs_to_slash(char *str)
 {
         char *p;
@@ -2193,15 +2218,6 @@ const char *need_system_drive(const char *path)
         return NULL;
 }
 
-/* Copy path to an allocated string long enough to allow a file extension
- * to be added. */
-char *alloc_ext_space(const char *path)
-{
-        char *s = xmalloc(strlen(path) + 5);
-        strcpy(s, path);
-        return s;
-}
-
 int chdir_system_drive(void)
 {
         const char *sd = get_system_drive();
diff --git a/win32/process.c b/win32/process.c
index 0585f66a6..a0678f50d 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -328,14 +328,12 @@ mingw_spawn_interpreter(int mode, const char *prog, char *const *argv,
         }
 #endif
 
-        path = alloc_ext_space(interp.path);
-        if ((add_win32_extension(path) || file_is_executable(path))) {
+        path = file_is_win32_exe(interp.path);
+        if (path) {
                 new_argv[0] = path;
                 ret = mingw_spawn_interpreter(mode, path, new_argv, envp, level);
                 goto done;
         }
-        free(path);
-        path = NULL;
 
         if (unix_path(interp.path)) {
                 if ((path = find_first_executable(interp.name)) != NULL) {
@@ -363,13 +361,12 @@ mingw_spawnvp(int mode, const char *cmd, char *const *argv)
                 return mingw_spawn_applet(mode, argv, NULL);
 #endif
         if (has_path(cmd)) {
-                path = alloc_ext_space(cmd);
-                if (add_win32_extension(path) || file_is_executable(path)) {
+                path = file_is_win32_exe(cmd);
+                if (path) {
                         ret = mingw_spawn_interpreter(mode, path, argv, NULL, 0);
                         free(path);
                         return ret;
                 }
-                free(path);
                 if (unix_path(cmd))
                         cmd = bb_basename(cmd);
         }