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8969 :: C/C++-wrapping Windows/VCC-related issues again

• drkameleon (orginal) [2022-03-02T10:53:55+01:00] view original

  So... I'm still struggling with the Webview wrapper for Nim (very, very close to get it right; but a couple of issues still popping up)

  So...

  Important Note: I'm compiling as C++ with VCC/cl.exe. (the exact same thing compiles fine & works flawlessly for Clang/macOS & GCC/Linux)

  Here's my type definition (at least the relevant ones):

  type
       Webview* {.importc: "webview_t".} = pointer
       WebviewCallback* = proc (seq: cstring, req: cstring, arg: pointer) {.cdecl.}
  Run

  Here's the function import:

  proc webview_bind*(w: Webview, name: cstring, cb: WebviewCallback, arg: pointer) {.importc.}
  Run

  Here's how the exact same thing is declared in webview.h (C/C++):

  WEBVIEW_API void webview_bind(webview_t w, const char *name,
                                void (*fn)(const char *seq, const char *req,
                                           void *arg),
                                void *arg);
  Run

  And here's the error code I'm getting (from the CI build, since I don't have a Windows machine):

  
  @mhelpers@swebviews.nim.cpp
  D:\a\arturo\arturo\.cache\@mhelpers@swebviews.nim.cpp(1286): error C2664: 'void webview_bind(webview_t,const char *,void (__cdecl *)(const char *,const char *,void *),void *)': cannot convert argument 3 from 'tyProc__6j8G629bS5b9a9a48K9cMq8U9aA' to 'void (__cdecl *)(const char *,const char *,void *)'
  D:\a\arturo\arturo\.cache\@mhelpers@swebviews.nim.cpp(1286): note: This conversion requires a reinterpret_cast, a C-style cast or parenthesized function-style cast
  D:\a\arturo\arturo\src\extras\webview/webview.h(98): note: see declaration of 'webview_bind'
  Run

  If you ask me (and Clang/GCC), I'm already doing right - and the correspondence between the argument definitions is correct. If you ask VCC/cl, it seems to... disagree.

  Any ideas?

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• drkameleon (orginal) [2022-03-02T11:16:37+01:00] view original

  OK, I think I've spotted it:

  I'm declaring WebviewCallback's seq & req as cstring (which - from what I've seen - means char*), while the actual seq & req are declared as const char*.

  Now, let's see how I can get around this...

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• drkameleon (orginal) [2022-03-02T11:21:17+01:00] view original

  Attempting this:

  type
       ccstring {.importc:"const char*".} = cstring
       WebviewCallback* = proc (seq: ccstring, req: ccstring, arg: pointer) {.cdecl.}
  Run

  Again, it has already compiled fine on Mac - let's see what sort of surprise comes up from the Windows build.

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• drkameleon (orginal) [2022-03-02T11:29:52+01:00] view original

  Update: Still nothing at all. The exact same error message remains intact... :S

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• PMunch (orginal) [2022-03-02T11:32:43+01:00] view original

  From the error it seems like the callback you're passing in is not declared properly

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• drkameleon (orginal) [2022-03-02T11:33:12+01:00] view original

  Attempting to also change the definition of the passed proc in the caller function (which I previously forgot).

  Again, Mac works fine. Waiting for the Windows build...

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• drkameleon (orginal) [2022-03-02T11:34:38+01:00] view original

  Looks like it. I changed the callback's params to this new ccstring type. I'll let you know in a moment...

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• drkameleon (orginal) [2022-03-02T12:02:12+01:00] view original

  So... final update: I got it to work.

  Apart from the changes mentioned above:

  1. I changed the argument definitions in the callback (from cstring to ccstring)
  2. every time I used one of these params (seq and req) within the callback, I cast them to cstring, like:

  cast[cstring](seq)
  Run

  Now, my only issue is VCC/cl itself I guess. The linking stage takes ages to complete (~60 minutes compared to 5-6 minutes on Linux/Mac CI builds), but I have no idea why.

  I want(ed) to use MINGW, but then the issue is that I get one ton of other unrelated errors (because of the Webview2-related libraries) + I've seen that it's very challenging. So, I decided to abandon the idea and go for VCC.

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