String Manipulation when using the C API

[FuriousBee (Lizi Attwood)]

Hi all,

We received our playdate a while back and I’ve been happily playing with it off and on ever since!

I know C better than I know Lua so I went straight for that. I didn’t have much luck getting anything building in Windows for C including the examples but I did have more success on the Mac, so I swapped over to using Xcode to build and have started making a little game.

I tried to use snprintf to put an integer into a string before displaying it. This gave me a compile error and after a bit of investigating it seems as though there probably just isn’t support for that method?

FYI the error read: undefined reference to `_sbrk'

I’ve searched the forums and it seems like most people are using Lua which has string manipulation built in. Perhaps I should have just gone straight for Lua but I thought I’d be more comfortable in C!

Any help is much appreciated, perhaps there is a more obvious way that I’ve overlooked? Right now I'm thinking that I need to write my own method for stringifying a number?

[mistermo (Mobeen Fikree)]

This stumped me for a bit as well! The good news is that you don't need to write it yourself, the SDK includes a format string API:

// make a formatted string
char* str;
pd->system->formatString(&str, "Hello, world! %d", 123);

// (do stuff with str)

// release it
pd->system->realloc(str, 0);

(It's worth noting that other string functions, like strlen, are supported)

It's definitely worth looking through the "Inside Playdate with C" doc as well as the C API header files when you get stuck.

[FuriousBee (Lizi Attwood)]

Oh cool, thanks so much. Yeah, I tested the other string functions worked ok and I could see that it was to do with the fact that function needs to allocate. Also, I read through "Inside Playdate with C" but I guess not thoroughly enough!

Thanks so much for your help!

[Nic (Nic Magnier)]

Mistermo already answer your question but related to your _sbrk issue I was able to fix it in a project by adding a compiler option.

In the cmakelists.txt I’ve added
add_link_options(-specs=nano.specs -specs=nosys.specs)

Doom on Playdate

Last week end I finally started to work on porting Doom on the Playdate. This is a very early result, just to run the game, but that was the hardest part for me. Dealing with makefiles and compiler is really not my cup of tea so having the game running means that now I can focus on the game control, presentation and optimization. [04] This is a gif from the simulator but I got the game running on the hardware too. [05] The most difficult part was to deal with the linker that was complaining…

Not sure if that would make it possible to use snprintf though...

[FuriousBee (Lizi Attwood)]

Thanks for the additional info Nic!
I had also found that linker option whilst searching but couldn't work out where I needed to put it. Building with makefiles also not something I've spent a lot of time doing, not recently at least!