wasm Web assembly module

[mariomotta]

Please,
could someone explain to me what are the real advantages of using a wasm instead of a dll module?
For the moment I don't see them, debugging is limited to code flow, auto and local var values only, but above all the translation from C ++ to wasm is opaque,.
I have tried a piece of c ++ code which is apparently correct and works perfectly when compiled as dll but instead crashes the simulator when compiled as wasm with no possibility of knowing why.
For instance a simple simconnect_open made from a gauge callback makes the sim crash despite the SDK reports is that possible.
It crashes silent even before the C++ debugger can catch the code
I could not make any of my examples work and also the SampleGaugeAircarft example compiled from SDK crashes frequently.
The only gauge i could see working is a simple void gauge :-(

 

[DragonflightDesign]

WASM is a complete sandbox. A faulty WASM won't bring the rest of the program to a spluttering halt, but a misbehaving dll will. Web Assembly 101:

Modules — WebAssembly 2.0 (Draft 2024-03-05)

- provided you understand another low-level language (C/ C++).

 

[mariomotta]

thanks for reply,
due my poor english may be i did not made me understood, not meant in general the advantages of a LLVM, but in this particular case, they claim to support legacy C++ modules with so many drawbacks, may be is worth to write directly the code in wasm text using tools to compile /debug the source.
Just my opinion, at present all my effort to write a non-trivial gaugein C++ compiled to a wasm module were unsuccessfull.

 

[mariomotta]

Just to make an example:

#include "stdio.h"
#include "ssw_wasm_gauges.h" 
PCSTRINGZ custom_event_id_name = "custom_event_id"; 
struct CustomEventID {    
    ID id;
    ENUM value; 
}; 
CustomEventID custom_event_id = { 0,0 }; 
// Callbacks 
extern "C" {   
 MSFS_CALLBACK bool custom_event_gauge_callback(FsContext ctx, int service_id, void* pData)    {
        switch (service_id)
        {        
case PANEL_SERVICE_PRE_INSTALL: 
       {
            ID id = 0; 
           //custom_event_id.id = register_named_variable(custom_event_id_name);
           id = custom_event_id.id; 
           return true;        
        }        break; 
       case PANEL_SERVICE_POST_INSTALL: 
      // other code void

This code run nicely, it's enough uncomment:

custom_event_id.id = register_named_variable(custom_event_id_name);

to crash the sim executable, the module that triggers the seems to be ntdll.dll

 

[WarpD]

Do you have an actual gauge header defined? Without a gauge header, I do not believe that there is any access to the C++ gauge functions. The function is referenced directly from the ImportTable which you have to declare for the sim to be able to populate it. The declaration is automatic if you have a GaugeTable defined using GAUGE_TABLE_BEGIN.

 

[mariomotta]

Thanks for reply, but things seems quite different, the legacy gauges.h seems not applicable.
Using GAUGE_TABLE_BEGIN. gives compilation errors.
Please may you post a simple example of a gauge ?
tia

 

[mariomotta]

With latest 1.8.3.0 release above flaw seems gone, cross fingers !