批量在nimlang中用模板/宏创建了C接口？

Question

BackGround

事实上，我正在将FLTK C 1.3.3 for FreeBASIC移植到nimlang。请注意FLTK C 1.3.3 for FreeBASIC是FLTK in CPP上的C接口。

例如，DLL中的许多函数都符合相同的类似名称格式

#inclib "fltk-c-1.3.3-64" ' Windows 64-bit

function Fl_ButtonExNew (byval x as long, byval y as long, byval w as long, byval h as long, byval title as const zstring ptr=0) as Fl_ButtonEx Ptr
sub Fl_ButtonExDelete(byval x as Fl_ButtonEx ptr)

function Fl_BoxExNew (byval x as long, byval y as long, byval w as long, byval h as long, byval title as const zstring ptr=0) as Fl_BoxEx Ptr
sub Fl_BoxExDelete(byval x as Fl_BoxEx ptr)

and so on

并且似乎delcared函数/ sub会自动加载fltk-c-1.3.3-64.dll中的同名函数（如果错误，请纠正我）

Solution in FreeBASIC

所以在FreeBASIC标题fltk-main.bi中，有一个辅助宏

#macro DeclareEx(_name_)
declare function _name_##ExNew(byval x as long, byval y as long, byval w as long, byval h as long, byval title as const zstring ptr=0) as _name_##Ex ptr
declare sub      _name_##ExDelete         (byref ex as _name_##Ex ptr)
#endmacro

借助于此，上面的代码（以及许多其他代码）可以通过简单的一行代码生成：

DeclareEx(Fl_Button)
DeclareEx(Fl_Box)

My question in nimlang

在nimlang中（请暂时忽略数字类型转换），上述代码可以手动翻译为

const fltk = "fltk-c-1.3.3-64.dll"
type long = int64
proc Fl_ButtonExNew (x: long, y: long, w: long, h: long, title: cstring=nil): Ptr Fl_ButtonEx {.cdecl, importc: "Fl_ButtonExNew", dynlib: fltk, discardable.}
proc Fl_ButtonExDelete(x: ptr Fl_ButtonEx) {.cdecl, importc: "Fl_ButtonExDelete", dynlib: fltk, discardable.}

proc Fl_BoxExNew (x: long, y: long, w: long, h: long, title: cstring=nil): Ptr Fl_BoxEx {.cdecl, importc: "Fl_BoxExNew", dynlib: fltk, discardable.}
proc Fl_BoxExDelete(x: ptr Fl_BoxEx) {.cdecl, importc: "Fl_BoxExDelete", dynlib: fltk, discardable.}

所以我试着模仿FreeBASIC宏的作用

const fltk = "fltk-c-1.3.3-64.dll"
type long = int64

template DeclareEx*(name: untyped) {.dirty.}=
    type `name Ex` = object
    type `name ExNew`* = proc(x: long, y: long, w: long, h: long, title: cstring=nil): ptr `name Ex` {.cdecl, importc: "name New", dynlib: fltk, discardable.}
    type `name ExDelete`*  = proc(ex: ptr `name Ex`) {.cdecl, importc: "name ExDelete", dynlib: fltk, discardable.}

DeclareEx(Fl_Button)

但是当我编译它时，我得到了

d.nim（9,10）模板/来自这里的DeclareEx的通用实例化

d.nim（6,118）错误：无效的pragma：importc：“name New”

那么，任何解决方案？谢谢

Answer 1

模板中提供的反引号插值只能用于预期标识符的位置。 importc编译指示期望一个常量字符串表达式。你可以使用astToStr magic将任何AST输入转换为相应的字符串表示，这是解决方案的关键：

const fltk = "fltk-c-1.3.3-64.dll"
type long = int64

template DeclareEx*(name: untyped) =
  const
    newProc = astToStr(name) & "New"
    deleteProc = astToStr(name) & "ExDelete"

  type `name Ex`* {.inject.} = object
  proc `name ExNew`*(x: long, y: long, w: long, h: long, title: cstring=nil): ptr `name Ex` {.cdecl, inject, importc: newProc, dynlib: fltk, discardable.}
  proc `name ExDelete`* (ex: ptr `name Ex`) {.cdecl, inject, importc: deleteProc, dynlib: fltk, discardable.}

DeclareEx(Fl_Button)
DeclareEx(Fl_Window)

var btn: ptr Fl_ButtonEx
Fl_ButtonExDelete(btn)

Answer 2

importc pragma用于从C导入proc或变量。但是，您正在编写importc: "name New"，而name New不是C中的有效标识符，因为它中有空格。您需要尝试将传递给模板的变量的符号名称与附加字符串sufix连接起来。

不过，我不知道你怎么能在模板中做到这一点。也许你可以传递一个字符串作为参数，然后使用&运算符将它与importc的后缀连接起来。