// vim: ts=4 sw=4 expandtab ft=c

// Copyright (C) 1996-1997, 1999-2000, 2002, 2006 The University of Melbourne.
// Copyright (C) 2016, 2018 The Mercury team.
// This file is distributed under the terms specified in COPYING.LIB.

// prof_mem.c
//
// Author:  petdr
//
// This module is needed to get around the problem that when a signal occurs
// it may be in a malloc. The handling routine may also do a malloc, which
// stuffs up the internal state of malloc and cause a seg fault.
// If we are using the conservative GC, that doesn't cause a problem,
// since the Boehm et al collector is signal safe. But if we are not
// using the conservative GC, then the handler will need to call malloc().
// To minimize this problem, we use our own version of malloc() which
// allocates memory in large chunks, reducing the chance of this
// problem occurring.

#include "mercury_imp.h"

#include <stdio.h>

#include "mercury_prof_mem.h"

#include "mercury_memory.h" // for MR_GC_malloc()
#include "mercury_dword.h"  // for MR_Dword

////////////////////////////////////////////////////////////////////////////

// Constants.

#define MEMORY_BLOCK    8192
// Testing on a big input file on the compiler
// normally required around 6000 nodes.

////////////////////////////////////////////////////////////////////////////

// Private Global Variables.

static size_t   mem_left = 0;       // Number of bytes left.
static char     *next    = NULL;    // Pointer to next data block
                                    // we can give away.

////////////////////////////////////////////////////////////////////////////

void *
MR_prof_malloc(size_t size)
{
    register void *p;

    // Ensure all allocations are word-aligned, by rounding size
    // up to the nearest multiple of the word size.
    //
    // Note that the current implementation of MR_prof_malloc only guarantees
    // that the memory will be MR_Dword-aligned; if you want to allocate types
    // that contain data types (e.g. `double') which might require stricter
    // alignment than that, then you will need to change this to
    // round the size up accordingly.

    size = ((size + sizeof(MR_Dword) - 1) / sizeof(MR_Dword))
        * sizeof(MR_Dword);

    // Here we waste a bit of space, but hopefully not to much.
    if (mem_left < size) {
        next = MR_GC_malloc_uncollectable_attrib(MEMORY_BLOCK * size,
            MR_ALLOC_SITE_RUNTIME);
        mem_left = MEMORY_BLOCK * size;
    }

    p = (void *) next;

    next += size;
    mem_left -= size;

    return p;
}

////////////////////////////////////////////////////////////////////////////