libphobos/libdruntime/gcc/sections/win32.d

// Win32-specific support for sections.
// Copyright (C) 2019-2020 Free Software Foundation, Inc.

// GCC is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 3, or (at your option) any later
// version.

// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

module gcc.sections.win32;

version (CRuntime_DigitalMars):

// debug = PRINTF;
debug(PRINTF) import core.stdc.stdio;
import rt.minfo;
import core.stdc.stdlib : malloc, free;

struct SectionGroup
{
    static int opApply(scope int delegate(ref SectionGroup) dg)
    {
        return dg(_sections);
    }

    static int opApplyReverse(scope int delegate(ref SectionGroup) dg)
    {
        return dg(_sections);
    }

    @property immutable(ModuleInfo*)[] modules() const nothrow @nogc
    {
        return _moduleGroup.modules;
    }

    @property ref inout(ModuleGroup) moduleGroup() inout nothrow @nogc
    {
        return _moduleGroup;
    }

    @property inout(void[])[] gcRanges() inout nothrow @nogc
    {
        return _gcRanges[];
    }

private:
    ModuleGroup _moduleGroup;
    void[][] _gcRanges;
}

shared(bool) conservative;

void initSections() nothrow @nogc
{
    _sections._moduleGroup = ModuleGroup(getModuleInfos());

    import rt.sections;
    conservative = !scanDataSegPrecisely();

    if (conservative)
    {
        _sections._gcRanges = (cast(void[]*) malloc(2 * (void[]).sizeof))[0..2];

        auto databeg = cast(void*)&_xi_a;
        auto dataend = cast(void*)_moduleinfo_array.ptr;
        _sections._gcRanges[0] = databeg[0 .. dataend - databeg];

        // skip module info and CONST segment
        auto bssbeg = cast(void*)&_edata;
        auto bssend = cast(void*)&_end;
        _sections._gcRanges[1] = bssbeg[0 .. bssend - bssbeg];
    }
    else
    {
        size_t count = &_DPend - &_DPbegin;
        auto ranges = cast(void[]*) malloc(count * (void[]).sizeof);
        size_t r = 0;
        void* prev = null;
        for (size_t i = 0; i < count; i++)
        {
            void* addr = (&_DPbegin)[i];
            if (prev + (void*).sizeof == addr)
                ranges[r-1] = ranges[r-1].ptr[0 .. ranges[r-1].length + (void*).sizeof];
            else
                ranges[r++] = (cast(void**)addr)[0..1];
            prev = addr;
        }
        _sections._gcRanges = ranges[0..r];
    }
}

void finiSections() nothrow @nogc
{
    free(_sections._gcRanges.ptr);
}

void[] initTLSRanges() nothrow @nogc
{
    auto pbeg = cast(void*)&_tlsstart;
    auto pend = cast(void*)&_tlsend;
    return pbeg[0 .. pend - pbeg];
}

void finiTLSRanges(void[] rng) nothrow @nogc
{
}

void scanTLSRanges(void[] rng, scope void delegate(void* pbeg, void* pend) nothrow dg) nothrow
{
    if (conservative)
    {
        dg(rng.ptr, rng.ptr + rng.length);
    }
    else
    {
        for (auto p = &_TPbegin; p < &_TPend; )
        {
            uint beg = *p++;
            uint end = beg + cast(uint)((void*).sizeof);
            while (p < &_TPend && *p == end)
            {
                end += (void*).sizeof;
                p++;
            }
            dg(rng.ptr + beg, rng.ptr + end);
        }
    }
}

private:

__gshared SectionGroup _sections;

// Windows: this gets initialized by minit.asm
extern(C) __gshared immutable(ModuleInfo*)[] _moduleinfo_array;
extern(C) void _minit() nothrow @nogc;

immutable(ModuleInfo*)[] getModuleInfos() nothrow @nogc
out (result)
{
    foreach (m; result)
        assert(m !is null);
}
body
{
    // _minit directly alters the global _moduleinfo_array
    _minit();
    return _moduleinfo_array;
}

extern(C)
{
    extern __gshared
    {
        int _xi_a;      // &_xi_a just happens to be start of data segment
        int _edata;     // &_edata is start of BSS segment
        int _end;       // &_end is past end of BSS

        void* _DPbegin; // first entry in the array of pointers addresses
        void* _DPend;   // &_DPend points after last entry of array
        uint _TPbegin;  // first entry in the array of TLS offsets of pointers
        uint _TPend;    // &_DPend points after last entry of array
    }

    extern
    {
        int _tlsstart;
        int _tlsend;
    }
}