Leaf allows C-style string as error objects

[ericli-splunk]

Version of Boost

1.83.0

Actual and Expected Behavior

When running the following program

#include <string>
#include <iostream>
#include <boost/leaf/result.hpp>
#include <boost/leaf/handle_errors.hpp>

using namespace boost;

int main () {
    leaf::try_handle_all(
        []() -> leaf::result<void> {
            boost::leaf::throw_exception("foo");
        },
        [](std::string err) {
            std::cout << "std::string: " << err << std::endl;
        },
        [](const char* err) {
            std::cout << "const char*: " << (void *)err << std::endl;
        },
        []() {
            std::cout << "general" << std::endl;
        }
    );
    return 0;
}

Actual output:

const char*: 0

Expected Behavior:

• Compile error on line boost::leaf::throw_exception("foo"); saying something like "Error objects of pointer types are not allowed"

Explanation

Some people may expect the program to output "std::string: foo" or "const char*: 0x12345678". However, this is not the case because Leaf does not support pointer type error objects. Thus, I think my code should not compile.

It appears that the following code is designed to prevent my code from compiling

leaf/include/boost/leaf/error.hpp

Line 432 in 61e4b0d

static_assert(!std::is_pointer<E>::value, "Error objects of pointer types are not allowed");

However, my code compiles fine because e's type is const char (&)[4], not const char *. The latter is a pointer type, but the former is not.

Steps necessary to reproduce the problem

Compile and run using g++ a.cpp -o a -g && ./a

All relevant compiler information

g++ (Debian 14.2.0-19) 14.2.0

[zajo]

Thanks, this is a good catch.

[ericli-splunk]

I think #85 will fix this issue.

[zajo]

We should add a test also. I'll look into this in the next weekend.