/**
 * FreeBSD implementation of glibc's $(LINK2 http://www.gnu.org/software/libc/manual/html_node/Backtraces.html backtrace) facility.
 *
 * Copyright: Copyright Martin Nowak 2012.
 * License:   $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
 * Authors:   Martin Nowak
 * Source:    $(DRUNTIMESRC core/sys/freebsd/_execinfo.d)
 */
module core.sys.freebsd.execinfo;

version (FreeBSD):
extern (C):
nothrow:

import core.sys.freebsd.dlfcn;

// Use extern (D) so that these functions don't collide with libexecinfo.

extern (D) int backtrace(void** buffer, int size)
{
    import core.thread : thread_stackBottom;

    void** p, pend=cast(void**)thread_stackBottom();
    version (D_InlineAsm_X86)
        asm nothrow @trusted { mov p[EBP], EBP; }
    else version (D_InlineAsm_X86_64)
        asm nothrow @trusted { mov p[RBP], RBP; }
    else
        static assert(false, "Architecture not supported.");

    int i;
    for (; i < size && p < pend; ++i)
    {
        buffer[i] = *(p + 1);
        auto pnext = cast(void**)*p;
        if (pnext <= p) break;
        p = pnext;
    }
    return i;
}


extern (D) char** backtrace_symbols(const(void*)* buffer, int size)
{
    static void* realloc(void* p, size_t len) nothrow
    {
        static import cstdlib=core.stdc.stdlib;
        auto res = cstdlib.realloc(p, len);
        if (res is null) cstdlib.free(p);
        return res;
    }

    if (size <= 0) return null;

    size_t pos = size * (char*).sizeof;
    char** p = cast(char**)realloc(null, pos);
    if (p is null) return null;

    Dl_info info;
    foreach (i, addr; buffer[0 .. size])
    {
        if (dladdr(addr, &info) == 0)
            (cast(ubyte*)&info)[0 .. info.sizeof] = 0;
        fixupDLInfo(addr, info);

        immutable len = formatStackFrame(null, 0, addr, info);
        assert(len > 0);

        p = cast(char**)realloc(p, pos + len);
        if (p is null) return null;

        formatStackFrame(cast(char*)p + pos, len, addr, info) == len || assert(0);

        p[i] = cast(char*)pos;
        pos += len;
    }
    foreach (i; 0 .. size)
    {
        pos = cast(size_t)p[i];
        p[i] = cast(char*)p + pos;
    }
    return p;
}


extern (D) void backtrace_symbols_fd(const(void*)* buffer, int size, int fd)
{
    import core.sys.posix.unistd : write;
    import core.stdc.stdlib : alloca;

    if (size <= 0) return;

    Dl_info info;
    foreach (i, addr; buffer[0 .. size])
    {
        if (dladdr(addr, &info) == 0)
            (cast(ubyte*)&info)[0 .. info.sizeof] = 0;
        fixupDLInfo(addr, info);

        enum maxAlloca = 1024;
        enum min = (size_t a, size_t b) => a <= b ? a : b;
        immutable len = min(formatStackFrame(null, 0, addr, info), maxAlloca);
        assert(len > 0);

        auto p = cast(char*)alloca(len);
        if (p is null) return;

        formatStackFrame(p, len, addr, info) >= len || assert(0);
        p[len - 1] = '\n';
        write(fd, p, len);
    }
}


private void fixupDLInfo(const(void)* addr, ref Dl_info info)
{
    if (info.dli_fname is null) info.dli_fname = "???";
    if (info.dli_fbase is null) info.dli_fbase = null;
    if (info.dli_sname is null) info.dli_sname = "???";
    if (info.dli_saddr is null) info.dli_saddr = cast(void*)addr;
}


private size_t formatStackFrame(char* p, size_t plen, const(void)* addr, const ref Dl_info info)
{
    import core.stdc.stdio : snprintf;

    immutable off = addr - info.dli_saddr;
    immutable len = snprintf(p, plen, "%p <%s+%zd> at %s",
                             addr, info.dli_sname, off, info.dli_fname);
    assert(len > 0);
    return cast(size_t)len + 1; // + '\0'
}
