+ API to get exception info in host environment

packages/wasm-utils/fpmake.pp

@@ -73,7 +73,7 @@ begin
       T.Dependencies.AddUnit('wasm.regexp.api');
       T.Dependencies.AddUnit('wasm.regexp.shared');
       T.Dependencies.AddUnit('wasm.regexp.objects');
-      
+    T:=P.Targets.AddUnit('wasm.exceptions.pas');
 {$ifndef ALLPACKAGES}
     Run;
     end;

packages/wasm-utils/src/wasm.exceptions.pas

@@ -0,0 +1,93 @@
+{
+    This file is part of the Free Component Library
+
+    Export last exception info from Webassembly API.
+    Copyright (c) 2025 by Michael Van Canneyt [email protected]
+
+    See the file COPYING.FPC, included in this distribution,
+    for details about the copyright.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+
+ **********************************************************************}
+unit wasm.exceptions;
+
+{$mode objfpc}
+
+interface
+
+uses
+  {$IFDEF FPC_DOTTEDUNITS}
+  System.SysUtils;
+  {$ELSE}
+  SysUtils;
+  {$ENDIF}
+
+Type
+  TLastExceptionInfo = record
+    ClassName : AnsiString;
+    ClassNameLen : Integer;
+    Message : UTF8String;
+    MessageLen : Integer;
+    more : boolean;
+  end;
+  PLastExceptionInfo = ^TLastExceptionInfo;
+
+
+function GetLastExceptionInfo : PLastExceptionInfo;
+procedure FreeLastExceptionInfo(aInfo : PLastExceptionInfo);
+
+implementation
+
+function PopObjectStack : TObject; external name 'FPC_POPOBJECTSTACK';
+
+
+function GetLastExceptionInfo : PLastExceptionInfo;
+
+var
+  lExc : PExceptObject;
+  lMsg : UTF8String;
+  Obj : TObject;
+begin
+  Result:=nil;
+  lExc:=RaiseList;
+  if lExc=Nil then
+    exit;
+  Result:=New(PLastExceptionInfo);
+  Result^:=Default(TLastExceptionInfo);
+  if assigned(lExc.FObject) then
+    begin
+    Result^.ClassName:=LExc.FObject.ClassName;
+    if LExc.FObject is Exception then
+      begin
+      {$IF SizeOf(Char)=2}
+      Result^.Message:=UTF8Encode(Exception(LExc.FObject).Message);
+      {$ELSE}
+      Result^.Message:=Exception(LExc.FObject).Message;
+      {$ENDIF}
+      end
+    else
+      Result^.Message:=LExc.FObject.ToString;
+    Result^.ClassNameLen:=Length(Result^.ClassName);
+    Result^.MessageLen:=Length(Result^.Message);
+    end;
+  Result^.More:=Assigned(lExc.Next);
+  ReleaseExceptionObject;
+  Obj:=PopObjectStack;
+  Obj.Free;
+
+end;
+
+procedure FreeLastExceptionInfo(aInfo : PLastExceptionInfo);
+begin
+  Dispose(aInfo);
+end;
+
+exports
+  GetLastExceptionInfo,
+  FreeLastExceptionInfo;
+
+end.
+