would be nice to be able to compile with "-fno-exceptions"

[jyrkialakuijala]

Is your feature request related to a problem? Please describe.

I'd like to use NumCpp with a codebase that does not use exceptions.

Describe the solution you'd like

I'd like the code to compile with -fno-exceptions, today boost logging will fail with that.

Describe alternatives you've considered

1. Isolation wrappers on either the other codebase or NumCpp, but it seems a lot of work.

2. Hacking up boost to not to use exceptions, but also slightly difficult since in my code base many other uses of boost (behind isolation wrappers).

[jyrkialakuijala]

If I add the following function in my code, then it more or less works. It still fails in two boost::log::aux::attach_attribute_name_info(e, name); calls inside the boost library, but I'll try to get that fixed within the boost library itself. I believe it may be missing some #ifdef BOOST_NO_EXCEPTIONS accidentally.

#ifdef BOOST_NO_EXCEPTIONS
namespace boost {
  // Boost calls this when BOOST_NO_EXCEPTIONS is defined
  void throw_exception(std::exception const& e) {
    std::cerr << "Fatal Boost error (exceptions disabled): " << e.what() << "\n";
    std::abort();
  }
}
#endif

[jyrkialakuijala]

I tried to add ifdef BOOST_NO_EXCEPTIONS into Boost.Log, but failed.

See boostorg/log#254

I found a workaround to compile NumCpp without exceptions (such as Google's C++ codebase or other codebases where people try to optimize for binary size/performence). The workaround looks quite nasty, but at least it allows for compiling NumCpp code.

It could be better to drop the Boost.Log dependency if that is possible.

Copying the hack here in case someone needs to make progress without exceptions before this is resolved properly.

#include <iostream>

#ifdef BOOST_NO_EXCEPTIONS
namespace boost {
// ---- Terrible hack begins. ----
// Boost log hack that needs to be before including NumCpp.hpp,
// otherwise doesn't compile due to a -fno-exceptions conflict
namespace log {
namespace v2_st {  // v2_st is an invisible namespace because
// probably aux is brought into boost::log::aux with a using statement,
// we just need to insert the do_nothing into the original namespace.
namespace aux {
inline void do_nothing() {}
}  // namespace aux
}  // namespace v2_st
}  // namespace log
// Redefine this so that exception and attribute_name are not touched,
// then the referencing of the exception will not be happening.
// Due to -fno-exceptions the exception doesn't exist, so attempting
// to refer to it is an compilation error (deep inside boost logging).
#define attach_attribute_name_info(exception, attribute_name) do_nothing()
// ---- Terrible hack ends. -----

// The following looks like hack, too, but it is the proper boost
// approach to exceptions when compiling with -fno-exceptions.
// Boost calls this when BOOST_NO_EXCEPTIONS is defined.
void throw_exception(std::exception const& e) {
  std::cerr << "Fatal Boost error (exceptions disabled): "
            << e.what() << "\n";
  std::abort();
}
}  // namespace boost
#endif

// Include a NumCpp header using the path relative to google3/
#include "third_party/NumCpp/NumCpp.hpp"

#undef attach_attribute_name_info

int main(int argc, char* argv[]) {
  // Use a basic feature from NumCpp: Create a 2x2 NdArray
  nc::NdArray<int> a = {{1, 2}, {3, 4}};

  // Perform a simple element-wise operation
  nc::NdArray<int> b = a + a;

  std::cout << b << std::endl;

  std::cout << "NumCpp test successful" << std::endl;
  return 0;
}