Re: C++ API: Vector arguments / error detection

[David Malcolm <dmalcolm@redhat.com>]

On Sun, 2022-01-30 at 16:35 +0100, Marc Nieper-Wißkirchen via Jit
wrote:
> This is about two unrelated issues regarding the C++ API:
> 
> (1) At the moment, a lot of API functions like new_function take non-
> const
> referenced to vectors, e.g. std::vector <param> &params;
> 
> Can we change this into const references?  This way, one can write
> 
> auto param1 = ctxt.new_param (...);
> auto param2 = ctxt.new_param (...);
> auto func = new_function (..., {param1, param2}, ...);
> 
> instead of the more complicated and less convenient
> 
> auto param1 = ...;
> auto param2 = ...;
> auto params = std::vector {param1, param2};
> auto func = new_function (..., params, ...);

I wonder why they're not const already - maybe I just forgot?

Making the refs const sounds like a good idea to me.

> 
> (2) When using gccjit::context::compile_to_file, how can I check
> whether
> the compilation succeeded without errors or not? In libgccjit++.h no
> error
> is checked and no exception thrown.

Looks like I forgot to:
(a) give a return value to gcc_jit_context_compile_to_file, and
(b) add C++ bindings for gcc_jit_context_get_first_error and
gcc_jit_context_get_last_error.

Looks like fixing (a) would be an ABI break, bother (perhaps we could
add a revised gcc_jit_context_compile_to_file symbol and do it with
symbol versioning)

With those in place, it looks like either the client code needs to
check gcc::jit::context::get_last_error on failure, or, better, it
should probably change to look something like this (untested):

inline void
context::compile_to_file (enum gcc_jit_output_kind output_kind,
			  const char *output_path)
{
  if (gcc_jit_context_compile_to_file (m_inner_ctxt,
				       output_kind,
				       output_path))
    throw error (m_inner_ctxt);
}

where error's ctor should call gcc::jit::context::get_last_error on the
ctxt, or something similar to this.


Sorry about the C++ API being much less polished that the C API.

Dave