E2591 Only cdecl functions may use varargs (Delphi)
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This error occurs whenever the varargs directive is used with non-cdecl functions.
function test(): Integer; varargs;
begin
end;
To fix this error, you need to declare your function with the external and cdecl directives:
function test(): Integer; varargs; cdecl; external 'externalLibrary.dll'; //This imports functions from a dynamically loadable library.
begin
end.
Note: This only occurs by compiling with the Delphi Mobile Compilers (dccios32, dcciosarm or dcciosarm64). Otherwise, the code produces E2277 Only external cdecl functions may use varargs (Delphi).