help with void * and nb::any

[Ziqi-Yang]

I want to bind these two functions:

/**
 * This function will search through all previously loaded dynamic
 * libraries for the symbol \p symbolName. If it is found, the address of
 * that symbol is returned. If not, null is returned.
 *
 * @see sys::DynamicLibrary::SearchForAddressOfSymbol()
 */
void *LLVMSearchForAddressOfSymbol(const char *symbolName);

/**
 * This functions permanently adds the symbol \p symbolName with the
 * value \p symbolValue.  These symbols are searched before any
 * libraries.
 *
 * @see sys::DynamicLibrary::AddSymbol()
 */
void LLVMAddSymbol(const char *symbolName, void *symbolValue);

My current attempt is this:

  m.def("get_symbol_value",
        [](const char *symbolName) -> nb::any {
          // ERROR cannot convert
          return LLVMSearchForAddressOfSymbol(symbolName);
        },
        "name"_a,
        "This function will search through all previously loaded dynamic"
        "libraries for the symbol symbolName. If it is found, the address of"
        "that symbol is returned. If not, null is returned.");

  m.def("add_symbol",
        [](const char *symbolName, nb::any symbolValue) {
          // ERROR, but compilation can pass: the passed value is nb::any*, but not void *
          return LLVMAddSymbol(symbolName, &symbolValue);
        },
        "symbol_name"_a, "symbol_value"_a,
        "This functions permanently adds the symbol symbolName with the"
        "value symbolValue.  These symbols are searched before any"
        "libraries.");

The error is noted in the comment.
Thanks!

[wjakob]

You can simply return void *. Nanobind will cast this into an opaque Capsule object (both ways -- returning and accepting values is accepted). nb::any is the wrong type to use here, because it assumes that you are returning something which is already a Python object.

Otherwise, you could also completely abstract away the object by binding a custom struct Symbol { void *addr; } typing along with accessor method bindings that unwrap Symbol.