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/*
* Copyright © 2024 Michael Smith <mikesmiffy128@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*/
#ifndef INC_ABI_H
#define INC_ABI_H
#include "intdefs.h"
/*
* This file defines miscellaneous C++ ABI stuff. Looking at it may cause brain
* damage and/or emotional trauma.
*/
#ifdef _WIN32 // Windows RTTI stuff, obviously only used on Windows.
// also this: number of virtual destructor entries (used all over the place)
#define NVDTOR 1
// MSVC RTTI is quite a black box, but thankfully there's some useful sources:
// - https://doxygen.reactos.org/d0/dcf/cxx_8h_source.html
// - https://blog.quarkslab.com/visual-c-rtti-inspection.html
// - https://www.geoffchappell.com/studies/msvc/language/predefined/
// - https://docs.rs/pelite/0.5.0/src/pelite/pe32/msvc.rs.html
// By the way, while I'm here I'd just like to point out how ridiculous this
// layout is. Whoever decided to put this many levels of indirection over what
// should be a small lookup table is an absolute nutcase. I hope that individual
// has gotten some help by now, mostly for the sake of others.
struct msvc_rtti_descriptor_head {
void **vtab;
void *unknown; // ???
// descriptor includes this, but constant flexible arrays are annoying, so
// this structure is just the header part and the string is tacked on in the
// DEF_MSVC_BASIC_RTTI macro below
//char classname[];
};
// "pointer to member displacement"
struct msvc_pmd { int mdisp, pdisp, vdisp; };
struct msvc_basedesc {
const struct msvc_rtti_descriptor_head *desc;
uint nbases;
struct msvc_pmd where;
uint attr;
};
struct msvc_rtti_hierarchy {
uint sig;
uint attrs;
uint nbaseclasses;
const struct msvc_basedesc **baseclasses;
};
struct msvc_rtti_locator {
uint sig;
int baseoff;
// ctor offset, or some flags; reactos and rust pelite say different things?
int unknown;
const struct msvc_rtti_descriptor_head *desc;
const struct msvc_rtti_hierarchy *hier;
};
// I mean seriously look at this crap!
#define DEF_MSVC_BASIC_RTTI(mod, name, vtab, typestr) \
mod const struct msvc_rtti_locator name; \
static const struct { \
struct msvc_rtti_descriptor_head d; \
char classname[sizeof("" typestr)]; \
} _desc_##name = {(vtab), 0, .classname = "" typestr}; \
static const struct msvc_basedesc _basedesc_##name = { \
&_desc_##name.d, 0, {0, 0, 0}, 0 \
}; \
mod const struct msvc_rtti_locator name = { \
0, 0, 0, \
&_desc_##name.d, \
&(struct msvc_rtti_hierarchy){ \
0, 1 /* match engine */, 1, \
(const struct msvc_basedesc *[]){&_basedesc_##name} \
} \
};
#else
#define NVDTOR 2 // *stupid* ABI, btw
struct itanium_type_info_vtable {
void *dtor1, *dtor2;
};
struct itanium_type_info {
struct itanium_type_info_vtable *vtable;
const char *name;
};
struct itanium_vmi_type_info {
struct itanium_type_info base;
uint flags;
uint nbases;
// then there's a flexible array of `__base_class_type_info`s, but for our
// purposes we can just have zero bases and avoid dealing with more nonsense
};
struct itanium_type_info_vtable_wrapper {
// Oh CHRIST, Unix RTTI is bonkers too. Each type_info is itself one of
// several subclasses with its own RTTI; the RTTI has RTTI!
ssize topoffset;
struct itanium_type_info *rtti;
struct itanium_type_info_vtable vtable;
};
// `typeinfo for __cxxabiv1::__vmi_class_type_info` in libcxxabi - type_info
// comparison is identity-based, so we need to import this from a shared object
// in order to implement the same ABI. I honestly don't know whether this or the
// MSVC design is more stupid.
extern struct itanium_type_info _ZTIN10__cxxabiv121__vmi_class_type_infoE;
// XXX: just static for now, as only used for cvars and lto would dedupe anyway.
static void _itanium_type_info_dtor(void *this) {}
#define DEF_ITANIUM_BASIC_RTTI(mod, name, typestr) \
mod const struct itanium_vmi_type_info name = { \
&(struct itanium_type_info_vtable_wrapper){ \
0, &_ZTIN10__cxxabiv121__vmi_class_type_infoE, \
(void *)&_itanium_type_info_dtor, (void *)&_itanium_type_info_dtor \
}.vtable, \
typestr, \
0, 0 \
};
#endif
#endif
// vi: sw=4 ts=4 noet tw=80 cc=80
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