How to use external C/C++ libraries? about godot-nim HOT 5 CLOSED

1. Don't use push/pop for specifying header, put it as a pragma in the corresponding proc/type.
2. .importcpp expects pattern as a value.
3. Use .compile pragma to compile .cpp file along with Nim files.
4. Use --cincludes:DIR to specify where to look for the header file.

This information can be found in the Nim manual.

Try this:

{.compile: "FastNoise.cpp".}

type
  FastNoise* {.header: "FastNoise.h", importcpp: "FastNoise".} = object

proc GetValue*(this: FastNoise, x: cfloat, y: cfloat): cfloat {.header: "FastNoise.h", importcpp: "#.GetValue(@)".}

from godot-nim.

1. Ok, but why?
2. I thought the name is taken from the procedure name and you only need it when you want a different name?
3. gotcha
4. im having problems with this

i did a quick test with a simple non godot project with a structure like so:

C:/Test/main.nim
C:/Test/fastnoise.nim
C:/Test/lib/FastNoise.h
C:/Test/lib/FastNoise.cpp

fastnoise.nim has the code you have kindly posted, then i use
nim c --cincludes:"C:\Test\lib\" --run "C:\Test\main.nim"
i get this error:
Error: unhandled exception: cannot open: FastNoise.cpp [IOError]

It's beginner level, i know :) but working with godot and external libs is important for me, i need to get this going. I want to take a switch from C# godot because i really like nim so far.

And in an actual godot project, how to use --cincludes with "nake build"? maybe in the nakefile.nim somewhere? or do i need to compile it once with nim?

thanks for your time

from godot-nim.

ok, im one step further.
cincludes only with root folder
nim c --cincludes:"C:\Test" --run "C:\Test\main.nim"
and in fastnoise.nim the subfolder:
{.compile: "lib/FastNoise.cpp".}

new error:

In file included from C:\Test\nimcache\main.c:11:0:
C:\Test/lib/FastNoise.h:45:1: error: unknown type name 'class'
 class FastNoise
 ^~~~~
C:\Test/lib/FastNoise.h:46:1: error: expected '=', ',', ';', 'asm' or '__attribute__' before '{' token
 {
 ^
C:\\Test\nimcache\main.c: In function 'GetNoise_9cku33tvANHm87a2gL2qUHQ':
C:\\Test\nimcache\main.c:80:2: error: unknown type name 'FastNoise'
  FastNoise obj;
  ^~~~~~~~~
C:\\Test\nimcache\main.c:87:11: error: request for member 'GetValue' in something not a structure or union
  T2_ = obj.GetValue(5.0000000000000000e+000, 8.0000000000000000e+000);

from godot-nim.

godot-nim-stub sample uses C backend to compile the code. You need to modify it to use C++. The line that compiles the main file is the last one in the build task of the nakefile: https://github.com/pragmagic/godot-nim-stub/blob/54e5d5c2526262b6e3a0b293676465b5bf615b88/nakefile.nim#L45

Change c to cpp and add any other parameters you need.

Re push/pop, I think they simply don't work in a way you used them. They can be used to override compiler settings, but not to assume that everything has a certain pragma on it.

And yeah, if you duplicate names it isn't necessary to specify them as .importcpp pragma values, but to be consistent with Nim style it's better to change the method name to lowercase. So in the end you should have something like this:

{.compile: "lib/FastNoise.cpp".}

type
  FastNoise* {.header: "FastNoise.h", importcpp.} = object

proc getValue*(this: FastNoise; x, y: cfloat): cfloat {.header: "FastNoise.h", importcpp: "GetValue".}

It's been a while since I last dealt with C++ interop, so might be something else that's needed here.

from godot-nim.

ok, fixing the test project above was simple, c to cpp
nim cpp --cincludes:"C:\Test\lib\" --run "C:\Test\main.nim" is working, GetValue does its job, nice

now to godot, not so easy though :/
changing c to cpp only gives error LNK2019: unresolved external symbol and nim64.dll: Fatal Error LNK1120: 1 unresolved externals
also Error: execution of an external program failed: 'vccexe.exe
im not importing fastnoise at all, just changing to cpp

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