err: Implement basis for new error API

[Geod24]

Fairly straightforward, didn't cover the full header though.

[CyberShadow]

Signature in docs seems to be:

void ERR_raise_data(int lib, int reason, const char *fmt, ...);

[Geod24]

Oh that's sneaky:
https://github.com/openssl/openssl/blame/4d346a188c27bdf78aa76590c641e1217732ca4b/include/openssl/err.h.in#L379-L382

Good thing we deprecated the comma operator for such code.

[Geod24]

Hum I don't think the FILE/LINE/FUNC thing can work with the same API.

[Geod24]

@CyberShadow : Updated. Not found of the API, but it's the only one that provides the same functionality (automatic file / line / func). Any suggestion / idea ?

[CyberShadow]

LGTM. I think an alternative which would be closer to the C macros would be to make ERR_raise_data a @property function which returns &ERR_set_error. Then, ERR_raise_data wouldn't need to copy ERR_set_error's signature.

[Geod24]

But it wouldn't get rid of the template bloat, which is my main concern.

Also I don't think it works:

import std.stdio;

void main ()
{
 	ERR_raise_data(42, 69, "Hello World");   
}

@property auto ERR_raise_data () ()
{
 	return &ERR_set_error;   
}

void ERR_set_error(int lib, int reason, string fmt)
{
 	writeln(fmt, " -- ", lib, " -- ", reason);   
}

onlineapp.d(5): Error: none of the overloads of template `onlineapp.ERR_raise_data` are callable using argument types `!()(int, int, string)`
onlineapp.d(8):        Candidate is: `ERR_raise_data()()`

You'll need two sets of parenthesis which IMO is not worth the cost for the benefit of avoiding duplication. YMMV.

[CyberShadow]

Right, I forgot properties are useless :(

I don't think you can do better without requiring object files.