Is there a way to manually allocate memory for reference typ

Question

Is there a way to manually allocate memory for reference types eg String Both the `alloc` and `allocArray` functions only handle primitive types

olonho · Answer

it seems there s some confusion between Kotlin object memory management and memory allocated for external world and accessible via interop It is very unlikely that you actually need custom placement for Kotlin objects such as kotlin String Typically when debugging interoperability memory issues existing memory debugging tools for native applications such as valgrind could be very helpful

olonho · Answer

for example for your case valgrind says ```==15941== Invalid read of size 8 ==15941== at 0x5F8CFFF nc Connect Items in usr lib x86 64 linux gnu libmenu so 5 9 ==15941== by 0x5F8E462 new menu in usr lib x86 64 linux gnu libmenu so 5 9 ==15941== by 0x436E24 ncurses kniBridge336 in home nike kotlin native curses kexe ==15941== by 0x436776 kfun ncurses new menu kotlinx cinterop CValuesRef lt kotlinx cinterop CPointerVarOf lt kotlinx cinterop CPointer lt ncurses tagITEM gt gt gt ValueType in home nike kotlin native curses kexe ==15941== by 0x4049C1 kfun main kotlin Array lt kotlin String gt curses kt 32 ==15941== by 0x404745 EntryPointSelector in home nike kotlin native curses kexe ==15941== by 0x4046B6 Konan start start kt 29 ==15941== by 0x404631 Konan run start curses kt 19 ==15941== by 0x4045A6 Konan main curses kt 19 ==15941== by 0x5796F44 below main libc start c 287 ==15941== Address 0x61c5410 is 0 bytes after a block of size 48 alloc d ==15941== at 0x4C2CC70 calloc in usr lib valgrind vgpreload memcheck amd64 linux so ==15941== by 0x433952 Kotlin interop malloc in home nike kotlin native curses kexe ==15941== by 0x413B0E kfun kotlinx cinterop nativeMemUtils alloc kotlin Long kotlin Int ValueType NativeMem kt 103 ==15941== by 0x4139CC kfun kotlinx cinterop nativeHeap alloc kotlin Long kotlin Int ValueType Utils kt 34 ==15941== by 0x413E69 kfun kotlinx cinterop ArenaBase alloc kotlin Long kotlin Int ValueType Utils kt 80 ==15941== by 0x413A77 kfun kotlinx cinterop NativePlacement alloc <http kotlin Int kotlin Int|kotlin Int kotlin Int> ValueType in home nike kotlin native curses kexe ==15941== by 0x4182E4 kfun kotlinx cinterop placeBytes internal Utils kt 229 ==15941== by 0x4181B9 kfun kotlinx cinterop object 2 getPointer internal Utils kt 239 ==15941== by 0x436762 kfun ncurses new menu kotlinx cinterop CValuesRef lt kotlinx cinterop CPointerVarOf lt kotlinx cinterop CPointer lt ncurses tagITEM gt gt gt ValueType in home nike kotlin native curses kexe ==15941== by 0x4049C1 kfun main kotlin Array lt kotlin String gt curses kt 32 ==15941== by 0x404745 EntryPointSelector in home nike kotlin native curses kexe ==15941== by 0x4046B6 Konan start start kt 29 ```

olonho · Answer

and `man new menu` clearly states that ```The function new menu creates a new menu connected to a specified item pointer array which must be NULL terminated ```

olonho · Answer

your last problem is the harder one although and related to design of curses API Essentially you need to pass a C string which is valid for longer time that just API call itself So somewhat kludgy approach is to avoid K N internal string conversion and manage the C pointers memory yourself See snippet below

olonho · Answer

``` import kotlinx cinterop import ncurses import kotlin system exitProcess val exitKeys = setOf e toInt E toInt val choices = arrayOf Choice 1 Choice 2 Choice 3 Choice 4 Exit val items = arrayOfNulls lt CPointer lt ITEM gt gt 6 var menu CPointer lt MENU gt = null var itemsValues CValuesRef lt CPointerVar lt ITEM gt gt = null fun main args Array lt String gt = memScoped setupScreen choices forEachIndexed pos c gt val name = c cstr getPointer this items pos = new item name name itemsValues = items toCValues getPointer this menu = new menu itemsValues if menu == null mvprintw 1 0 Error Cannot create menu exitProcess 1 else mvprintw 1 0 Menu created mvprintw 2 0 Press e to Exit mvprintw 3 0 Showing menu n refresh Show the menu post menu menu mvprintw 3 0 Reading key input n refresh readKeyInput cleanUp private fun setupScreen initscr cbreak noecho keypad stdscr true private fun cleanUp free menu menu items forEach free item it endwin private fun readKeyInput if menu = null var key Int do Read a character key = getch when key KEY DOWN gt menu driver menu REQ DOWN ITEM KEY UP gt menu driver menu REQ UP ITEM while key in exitKeys ```

olonho · Answer

also you need def file like that ```package = ncurses headers = ncurses h menu h headerFilter = ncurses h menu h noStringConversion = new item ```

napperley · Answer

So the key differences in the def file are the addition of the package headerFilter and noStringConversion entries where noStringConversion suppresses automatic String conversions for the `new item` function in the ncurses lib I see that the bindings will need to be regenerated slightly frowning face

olonho · Answer

key one is `noStringConversion` everything else you likely already had in place

olonho · Answer

didn t you produce ncurses bindings yourself already don t think they are in platform libs

napperley · Answer

Not a big issue with regenerating the bindings appears to be quicker generating them the 2nd time round smile