win32: rework adding of extensions to filenames

Previously there was one function to handle adding extensions to
executable filenames, add_win32_extension().  Refactor this into
three functions:

add_win32_extension() appends the suffix to the argument string
in-place.  The argument must be long enough to cope with this,
as is the case in ash where path_advance() adds 4 bytes to each
filename for just this reason.

alloc_win32_extension() is equivalent to the old add_win32_extension().
It allocates a string to hold the new filename then calls the new
add_win32_extension() function.  The caller is responsible for
managing the returned string.

auto_win32_extension() calls alloc_win32_extension() and saves the
resulting string using auto_string().  It's used where the new
filename is consumed immediately or the actual value isn't needed.

Rewrite code to use the most appropriate function.  Also reorder
some code in find_executable() and find_command().

1 files changed, 32 insertions, 20 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 707e6a3d2..08d955527 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -1160,7 +1160,7 @@ int mingw_rmdir(const char *path)
         return rmdir(path);
 }
 
-const char win_suffix[4][4] = { "com", "exe", "bat", "cmd" };
+static const char win_suffix[4][4] = { "com", "exe", "bat", "cmd" };
 
 static int has_win_suffix(const char *name, int start)
 {
@@ -1191,33 +1191,45 @@ int has_exe_suffix_or_dot(const char *name)
         return last_char_is(name, '.') || has_win_suffix(name, 0);
 }
 
-/* check if path can be made into an executable by adding a suffix;
- * return an allocated string containing the path if it can;
- * return NULL if not.
+/* 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.
  *
- * if path already has a suffix don't even bother trying
+ * If the return value is TRUE the argument contains the new path,
+ * if FALSE the argument is unchanged.
  */
-char *add_win32_extension(const char *p)
+int add_win32_extension(char *p)
 {
-        char *path;
-        int i, len;
-
-        if (has_exe_suffix_or_dot(p)) {
-                return NULL;
+        if (!has_exe_suffix_or_dot(p)) {
+                int i, len = strlen(p);
+
+                p[len] = '.';
+                for (i=0; i<4; ++i) {
+                        memcpy(p+len+1, win_suffix[i], 4);
+                        if (file_is_executable(p))
+                                return TRUE;
+                }
+                p[len] = '\0';
         }
+        return FALSE;
+}
 
-        len = strlen(p);
-        path = xasprintf("%s.com", p);
+/* Check if path can be made into an executable by adding a suffix.
+ * Return an allocated string containing the path if it can;
+ * return NULL if not.
+ *
+ * If path already has a suffix don't even bother trying.
+ */
+char *alloc_win32_extension(const char *p)
+{
+        if (!has_exe_suffix_or_dot(p)) {
+                int len = strlen(p);
+                char *path = strcpy(xmalloc(len+5), p);
 
-        for (i=0; i<4; ++i) {
-                memcpy(path+len+1, win_suffix[i], 4);
-                if (file_is_executable(path)) {
+                if (add_win32_extension(path))
                         return path;
-                }
+                free(path);
         }
-
-        free(path);
-
         return NULL;
 }