Brownian Bridge™

1. An XLL function is registered with the type string `"QQ"`. What does this mean?

The function takes no arguments and returns nothingThe function returns an `LPXLOPER12` and takes one `LPXLOPER12` argument — it can accept any Excel type (number, range, string) and return any Excel typeThe function takes two integer arguments and returns a `double`The function is a macro-type function that runs at workbook open

2. Memory allocated with `new` inside an XLL function and returned as the `lparray` of an `XLOPER12` will be automatically freed by Excel after the formula evaluation completes.

truefalse

3. In `xlAutoOpen`, you register a function with argument count `11` after `xlfRegister`. The actual number of `Excel12f` arguments after `xlfRegister` is 12 (the DLL handle + 10 registration strings). What happens if you pass `12` instead of `11`?

The function registers correctly — Excel ignores the extra argumentCompile error: `Excel12f` is variadic but validates argument counts at compile timeUndefined behaviour: the variadic `Excel12f` reads past the provided arguments on the stack, possibly crashing Excel or registering a corrupted functionThe function registers but requires an extra argument when called from a worksheet

4. You export a Black-Scholes pricing function `xBSCall(S, K, r, T, sigma)` as type `"BBBBBB"`. A trader enters `=xBSCall(A1, B1, 0.05, 1, C1)` where `A1` contains text. What does Excel pass to your function?

The function is not called — Excel shows `#VALUE!` immediatelyExcel passes `0.0` as the `double` argument for `A1`Excel attempts to coerce `A1` to a `double`; if the text cannot be converted, Excel passes a coerced error value and your function receives `#VALUE!` — but since the argument type is `B` (not `Q`), your function receives an undefined doubleExcel converts the text to a double using `atof` internally before calling your function

5. A colleague builds an XLL and loads it in 32-bit Excel. It crashes immediately. The same XLL loads fine in 64-bit Excel. What is the most likely cause?

The XLL uses C++17 features not supported by 32-bit compilersThe DLL was compiled as a 64-bit (`x64`) binary; a 64-bit DLL cannot be loaded by a 32-bit processThe `xlcall.h` header is different for 32-bit Excel32-bit Excel does not support the `XLOPER12` type

6. An XLL function declared with thread type `"1"` (single-threaded) can safely be called from a cell in a workbook that has Multi-Threaded Recalculation (MTR) enabled.

truefalse

Quiz: Exporting C++ to Excel via the XLL SDK

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