+ magically insert a void externref type in the System unit, called WasmExternRef

compiler/psystem.pas

@@ -441,6 +441,9 @@ implementation
         tarraydef(x86_m256dtype).elementdef:=s64floattype;
         tarraydef(x86_m256itype).elementdef:=s32floattype;
 {$endif x86}
+{$ifdef wasm}
+        wasmvoidexternreftype:=tcpupointerdefclass.create_externref(voidtype);
+{$endif wasm}
         set_default_ptr_types;
         openchararraytype:=carraydef.create_openarray;
         tarraydef(openchararraytype).elementdef:=cansichartype;
@@ -627,6 +630,10 @@ implementation
         addtype('$__m256d',x86_m256dtype);
         addtype('$__m256i',x86_m256itype);
 {$endif x86}
+{$ifdef wasm}
+        addtype('$wasm_void_externref',wasmvoidexternreftype);
+        addtype('WasmExternRef',wasmvoidexternreftype);
+{$endif wasm}
         addtype('$openchararray',openchararraytype);
         addtype('$file',cfiletype);
         if f_variants in features then
@@ -791,6 +798,9 @@ implementation
         loadtype('llvmbool1',llvmbool1type);
         loadtype('metadata',llvm_metadatatype);
 {$endif llvm}
+{$ifdef wasm}
+        loadtype('wasm_void_externref',wasmvoidexternreftype);
+{$endif wasm}
         loadtype('file',cfiletype);
         if target_info.system=system_i386_watcom then
           pvmt_name:='lower__pvmt'

compiler/symdef.pas

@@ -1157,6 +1157,9 @@ interface
        longintfarpointertype,     { used for MemL[] }
   {$endif i8086}
 {$endif x86}
+{$ifdef wasm}
+       wasmvoidexternreftype,
+{$endif wasm}
        cundefinedtype,
        cformaltype,               { unique formal definition }
        ctypedformaltype,          { unique typed formal definition }

compiler/wasm32/symcpu.pas

@@ -66,6 +66,7 @@ type
   public
     { flag, indicating whether the pointer is a WebAssembly externref reference type }
     is_wasm_externref: boolean;
+    constructor create_externref(def: tdef);
     function getcopy: tstoreddef; override;
     function GetTypeName: string; override;
   end;
@@ -248,6 +249,13 @@ implementation
     end;
 
 
+  constructor tcpupointerdef.create_externref(def: tdef);
+    begin
+      inherited create(def);
+      is_wasm_externref:=true;
+    end;
+
+
   function tcpupointerdef.getcopy: tstoreddef;
     begin
       result:=inherited;