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().