src/lib/data-stack.c

	data-stack.c revision 32c3ba3ba51c80d3fa2b4e17c34a621a8532cca0
2454dfa32c93c20a8522c6ed42fe057baaac9f9aStephan Bosch/* Copyright (c) 2002-2016 Dovecot authors, see the included COPYING file */
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen/* @UNSAFE: whole file */
0536ccb51d41e3078c3a9fa33e509fb4b2420f95Timo Sirainen
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#include "lib.h"
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#include "data-stack.h"
252db51b6c0a605163326b3ea5d09e9936ca3b29Timo Sirainen
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen
9511a40d933181045343110c8101b75887062aaeTimo Sirainen#ifdef HAVE_GC_GC_H
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#  include <gc/gc.h>
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#elif defined (HAVE_GC_H)
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#  include <gc.h>
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#endif
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen/* Initial stack size - this should be kept in a size that doesn't exceed
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen   in a normal use to avoid extra malloc()ing. */
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#ifdef DEBUG
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#  define INITIAL_STACK_SIZE (1024*10)
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#else
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#  define INITIAL_STACK_SIZE (1024*32)
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#endif
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#ifdef DEBUG
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#  define CLEAR_CHR 0xD5               /* D5 is mnemonic for "Data 5tack" */
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen#  define SENTRY_COUNT (4*8)
a94936bafd127680184da114c6a177b37ff656e5Timo Sirainen#  define BLOCK_CANARY ((void *)0xBADBADD5BADBADD5)      /* contains 'D5' */
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#  define BLOCK_CANARY_CHECK(block) i_assert((block)->canary == BLOCK_CANARY)
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#  define ALLOC_SIZE(size) (MEM_ALIGN(sizeof(size_t)) + MEM_ALIGN(size + SENTRY_COUNT))
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#else
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#  define CLEAR_CHR 0
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen#  define BLOCK_CANARY NULL
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#  define BLOCK_CANARY_CHECK(block) do { ; } while(0)
3f8303bae0f70df6db9337ad1d1476d290f9b1a3Timo Sirainen#  define ALLOC_SIZE(size) MEM_ALIGN(size)
3f8303bae0f70df6db9337ad1d1476d290f9b1a3Timo Sirainen#endif
3f8303bae0f70df6db9337ad1d1476d290f9b1a3Timo Sirainen
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainenstruct stack_block {
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    struct stack_block *next;
859cc94211b759825db5e15b0c88754da902ca14Timo Sirainen
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen    size_t size, left, lowwater;
859cc94211b759825db5e15b0c88754da902ca14Timo Sirainen    /* NULL or a poison value, just in case something accesses
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen       the memory in front of an allocated area */
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    void *canary;
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    /* unsigned char data[]; */
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen};
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen#define SIZEOF_MEMBLOCK MEM_ALIGN(sizeof(struct stack_block))
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen#define STACK_BLOCK_DATA(block) \
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    ((unsigned char *) (block) + SIZEOF_MEMBLOCK)
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen/* current_frame_block contains last t_push()ed frames. After that new
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen   stack_frame_block is created and it's ->prev is set to
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen   current_frame_block. */
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen#define BLOCK_FRAME_COUNT 32
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainenstruct stack_frame_block {
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    struct stack_frame_block *prev;
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    struct stack_block *block[BLOCK_FRAME_COUNT];
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    size_t block_space_used[BLOCK_FRAME_COUNT];
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    size_t last_alloc_size[BLOCK_FRAME_COUNT];
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen#ifdef DEBUG
1117aa7adc2909c750031fd7551a58a486d100d8Timo Sirainen    const char *marker[BLOCK_FRAME_COUNT];
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    /* Fairly arbitrary profiling data */
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    unsigned long long alloc_bytes[BLOCK_FRAME_COUNT];
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen    unsigned int alloc_count[BLOCK_FRAME_COUNT];
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen#endif
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen};
8887a9bb6d2e3f664cf741b763643a0e5610fa4dTimo Sirainen
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#ifdef DEBUG
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainenstruct data_stack_frame {
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen    int dummy;
01f4ee4a0243f3fe9af763e1a540cd5cff0d63f5Timo Sirainen};
a94936bafd127680184da114c6a177b37ff656e5Timo Sirainen#endif
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainendata_stack_frame_t data_stack_frame = 0;
07e4875d250e7a7157cd99132aafc773cf3cdf83Timo Sirainen
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainenstatic bool data_stack_initialized = FALSE;
2c0f1cb7a0564d48ec43c7315ea46ea38d2abd19Timo Sirainenstatic data_stack_frame_t root_frame_id;
2c0f1cb7a0564d48ec43c7315ea46ea38d2abd19Timo Sirainen
01f4ee4a0243f3fe9af763e1a540cd5cff0d63f5Timo Sirainenstatic int frame_pos = BLOCK_FRAME_COUNT-1; /* in current_frame_block */
2c0f1cb7a0564d48ec43c7315ea46ea38d2abd19Timo Sirainenstatic struct stack_frame_block *current_frame_block;
07e4875d250e7a7157cd99132aafc773cf3cdf83Timo Sirainenstatic struct stack_frame_block *unused_frame_blocks;
07e4875d250e7a7157cd99132aafc773cf3cdf83Timo Sirainen
07e4875d250e7a7157cd99132aafc773cf3cdf83Timo Sirainenstatic struct stack_block *current_block; /* block now used for allocation */
07e4875d250e7a7157cd99132aafc773cf3cdf83Timo Sirainenstatic struct stack_block *unused_block; /* largest unused block is kept here */
01f4ee4a0243f3fe9af763e1a540cd5cff0d63f5Timo Sirainen
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainenstatic struct stack_block *last_buffer_block;
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainenstatic size_t last_buffer_size;
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen#ifdef DEBUG
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainenstatic bool clean_after_pop = TRUE;
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen#else
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainenstatic bool clean_after_pop = FALSE;
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen#endif
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainenstatic bool outofmem = FALSE;
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainenstatic union {
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen    struct stack_block block;
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen    unsigned char data[512];
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen} outofmem_area;
01f4ee4a0243f3fe9af763e1a540cd5cff0d63f5Timo Sirainen
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainenstatic inline
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainenunsigned char *data_stack_after_last_alloc(struct stack_block *block)
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen{
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen    return STACK_BLOCK_DATA(block) + (block->size - block->left);
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen}
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainenstatic void data_stack_last_buffer_reset(bool preserve_data ATTR_UNUSED)
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen{
10c96a244935de4add8213ba0b894178dfb889a5Timo Sirainen    if (last_buffer_block != NULL) {
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#ifdef DEBUG
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen        unsigned char *last_alloc_end, *p, *pend;
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen
fe363b433b8038a69b55169da9dca27892ad7d18Timo Sirainen        last_alloc_end = data_stack_after_last_alloc(current_block);
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen        p = last_alloc_end + MEM_ALIGN(sizeof(size_t)) + last_buffer_size;
597dba3488c648ffb375ee4a552bd52ac4346979Timo Sirainen        pend = last_alloc_end + ALLOC_SIZE(last_buffer_size);
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen#endif
4aa7fe81503a20bc972ae625da4dd9e6996fbdbfTimo Sirainen        /* reset t_buffer_get() mark - not really needed but makes it
a94936bafd127680184da114c6a177b37ff656e5Timo Sirainen           easier to notice if t_malloc()/t_push()/t_pop() is called
a94936bafd127680184da114c6a177b37ff656e5Timo Sirainen           between t_buffer_get() and t_buffer_alloc().
4b9f99761df5014c659cd87fddaf6854af428cfcTimo Sirainen           do this before we get to i_panic() to avoid recursive
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen           panics. */
da2aa032ccfa8e7e4a4380ef738014549f4d2c2dTimo Sirainen        last_buffer_block = NULL;
c06f4017027263cf3a08becc551f5126409e2a83Timo Sirainen
411d6baa37f31d90730e90c4a28c43e1974bbe58Timo Sirainen#ifdef DEBUG
9511a40d933181045343110c8101b75887062aaeTimo Sirainen        while (p < pend)
2974dca6be5120e49279f06c8aa952e5fac56048Timo Sirainen            if (*p++ != CLEAR_CHR)
dd62b77c932d1b518f2a3e4bf80e36542becc256Timo Sirainen                i_panic("t_buffer_get(): buffer overflow");
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen        if (!preserve_data) {
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen            p = last_alloc_end;
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen            memset(p, CLEAR_CHR, SENTRY_COUNT);
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen        }
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen#endif
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen    }
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen}
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainendata_stack_frame_t t_push(const char *marker)
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen{
bdcb00145ad87765e3fd22d4ebc4d2c029a326b9Timo Sirainen    struct stack_frame_block *frame_block;

    frame_pos++;
    if (frame_pos == BLOCK_FRAME_COUNT) {
        /* frame block full */
        if (unlikely(!data_stack_initialized)) {
            /* kludgy, but allow this before initialization */
            frame_pos = 0;
            data_stack_init();
            return t_push(marker);
        }

        frame_pos = 0;
        if (unused_frame_blocks == NULL) {
            /* allocate new block */
#ifndef USE_GC
            frame_block = calloc(sizeof(*frame_block), 1);
#else
            frame_block = GC_malloc(sizeof(*frame_block));
#endif
            if (frame_block == NULL) {
                i_fatal_status(FATAL_OUTOFMEM,
                           "t_push(): Out of memory");
            }
        } else {
            /* use existing unused frame_block */
            frame_block = unused_frame_blocks;
            unused_frame_blocks = unused_frame_blocks->prev;
        }

        frame_block->prev = current_frame_block;
        current_frame_block = frame_block;
    }
    data_stack_last_buffer_reset(FALSE);

    /* mark our current position */
    current_frame_block->block[frame_pos] = current_block;
    current_frame_block->block_space_used[frame_pos] = current_block->left;
    current_frame_block->last_alloc_size[frame_pos] = 0;
#ifdef DEBUG
    current_frame_block->marker[frame_pos] = marker;
    current_frame_block->alloc_bytes[frame_pos] = 0ULL;
    current_frame_block->alloc_count[frame_pos] = 0;
#else
    (void)marker; /* only used for debugging */
#endif

    return data_stack_frame++;
}

data_stack_frame_t t_push_named(const char *format, ...)
{
    data_stack_frame_t ret = t_push(NULL);
#ifdef DEBUG
    va_list args;
    va_start(args, format);
    current_frame_block->marker[frame_pos] = p_strdup_vprintf(unsafe_data_stack_pool, format, args);
    va_end(args);
#else
    (void)format; /* unused in non-DEBUG builds */
#endif

    return ret;
}

static void free_blocks(struct stack_block *block)
{
    struct stack_block *next;

    /* free all the blocks, except if any of them is bigger than
       unused_block, replace it */
    while (block != NULL) {
        BLOCK_CANARY_CHECK(block);
        next = block->next;

        if (clean_after_pop)
            memset(STACK_BLOCK_DATA(block), CLEAR_CHR, block->size);

        if (unused_block == NULL || block->size > unused_block->size) {
#ifndef USE_GC
            free(unused_block);
#endif
            unused_block = block;
        } else {
#ifndef USE_GC
            if (block != &outofmem_area.block)
                free(block);
#endif
        }

        block = next;
    }
}

#ifdef DEBUG
static void t_pop_verify(void)
{
    struct stack_block *block;
    unsigned char *p;
    size_t pos, max_pos, used_size;

    block = current_frame_block->block[frame_pos];
    pos = block->size - current_frame_block->block_space_used[frame_pos];
    while (block != NULL) {
        BLOCK_CANARY_CHECK(block);
        used_size = block->size - block->left;
        p = STACK_BLOCK_DATA(block);
        while (pos < used_size) {
            size_t requested_size = *(size_t *)(p + pos);
            if (used_size - pos < requested_size)
                i_panic("data stack[%s]: saved alloc size broken",
                    current_frame_block->marker[frame_pos]);
            max_pos = pos + ALLOC_SIZE(requested_size);
            pos += MEM_ALIGN(sizeof(size_t)) + requested_size;

            for (; pos < max_pos; pos++) {
                if (p[pos] != CLEAR_CHR)
                    i_panic("data stack[%s]: buffer overflow",
                        current_frame_block->marker[frame_pos]);
            }
        }

        /* if we had used t_buffer_get(), the rest of the buffer
           may not contain CLEAR_CHRs. but we've already checked all
           the allocations, so there's no need to check them anyway. */
        block = block->next;
        pos = 0;
    }
}
#endif

bool t_pop(data_stack_frame_t *id)
{
    struct stack_frame_block *frame_block;

    if (unlikely(frame_pos < 0))
        i_panic("t_pop() called with empty stack");

    data_stack_last_buffer_reset(FALSE);
#ifdef DEBUG
    t_pop_verify();
#endif

    /* update the current block */
    current_block = current_frame_block->block[frame_pos];
    BLOCK_CANARY_CHECK(current_block);
    if (clean_after_pop) {
        size_t pos, used_size;

        pos = current_block->size -
            current_frame_block->block_space_used[frame_pos];
        used_size = current_block->size - current_block->lowwater;
        i_assert(used_size >= pos);
        memset(STACK_BLOCK_DATA(current_block) + pos, CLEAR_CHR,
               used_size - pos);
    }
    current_block->left = current_frame_block->block_space_used[frame_pos];
    current_block->lowwater = current_block->left;

    if (current_block->next != NULL) {
        /* free unused blocks */
        free_blocks(current_block->next);
        current_block->next = NULL;
    }

    if (frame_pos > 0)
        frame_pos--;
    else {
        /* frame block is now unused, add it to unused list */
        frame_pos = BLOCK_FRAME_COUNT-1;

        frame_block = current_frame_block;
        current_frame_block = frame_block->prev;

        frame_block->prev = unused_frame_blocks;
        unused_frame_blocks = frame_block;
    }
    if (unlikely(--data_stack_frame != *id))
        return FALSE;
    *id = 0;
    return TRUE;
}

static struct stack_block *mem_block_alloc(size_t min_size)
{
    struct stack_block *block;
    size_t prev_size, alloc_size;

    prev_size = current_block == NULL ? 0 : current_block->size;
    alloc_size = nearest_power(prev_size + min_size);

#ifndef USE_GC
    block = malloc(SIZEOF_MEMBLOCK + alloc_size);
#else
    block = GC_malloc(SIZEOF_MEMBLOCK + alloc_size);
#endif
    if (unlikely(block == NULL)) {
        if (outofmem) {
            if (min_size > outofmem_area.block.left)
                abort();
            return &outofmem_area.block;
        }
        outofmem = TRUE;
        i_panic("data stack: Out of memory when allocating %"
            PRIuSIZE_T" bytes", alloc_size + SIZEOF_MEMBLOCK);
    }
    block->size = alloc_size;
    block->left = 0;
    block->lowwater = block->size;
    block->next = NULL;
    block->canary = BLOCK_CANARY;

#ifdef DEBUG
    memset(STACK_BLOCK_DATA(block), CLEAR_CHR, alloc_size);
#endif
    return block;
}

static void *t_malloc_real(size_t size, bool permanent)
{
    void *ret;
    size_t alloc_size;
#ifdef DEBUG
    bool warn = FALSE;
    int old_errno = errno;
#endif

    if (unlikely(size == 0 || size > SSIZE_T_MAX))
        i_panic("Trying to allocate %"PRIuSIZE_T" bytes", size);

    if (unlikely(!data_stack_initialized)) {
        /* kludgy, but allow this before initialization */
        data_stack_init();
    }
    BLOCK_CANARY_CHECK(current_block);

    /* allocate only aligned amount of memory so alignment comes
       always properly */
    alloc_size = ALLOC_SIZE(size);
#ifdef DEBUG
    if(permanent) {
        current_frame_block->alloc_bytes[frame_pos] += alloc_size;
        current_frame_block->alloc_count[frame_pos]++;
    }
#endif
    data_stack_last_buffer_reset(TRUE);

    /* used for t_try_realloc() */
    current_frame_block->last_alloc_size[frame_pos] = alloc_size;

    if (current_block->left < alloc_size) {
        struct stack_block *block;

        /* current block is full, see if we can use the unused_block */
        if (unused_block != NULL && unused_block->size >= alloc_size) {
            block = unused_block;
            unused_block = NULL;
        } else {
            block = mem_block_alloc(alloc_size);
#ifdef DEBUG
            warn = TRUE;
#endif
        }

        block->left = block->size;
        block->next = NULL;
        current_block->next = block;
        current_block = block;
    }

    /* enough space in current block, use it */
    ret = data_stack_after_last_alloc(current_block);

    if (current_block->left - alloc_size < current_block->lowwater)
        current_block->lowwater = current_block->left - alloc_size;
    if (permanent)
        current_block->left -= alloc_size;

#ifdef DEBUG
    if (warn && getenv("DEBUG_SILENT") == NULL) {
        /* warn after allocation, so if i_debug() wants to
           allocate more memory we don't go to infinite loop */
        i_debug("Growing data stack by %"PRIuSIZE_T" as "
              "'%s' reaches %llu bytes from %u allocations.",
              current_block->size,
              current_frame_block->marker[frame_pos],
              current_frame_block->alloc_bytes[frame_pos],
              current_frame_block->alloc_count[frame_pos]);
    }
    memcpy(ret, &size, sizeof(size));
    ret = PTR_OFFSET(ret, MEM_ALIGN(sizeof(size)));
    /* make sure the sentry contains CLEAR_CHRs. it might not if we
       had used t_buffer_get(). */
    memset(PTR_OFFSET(ret, size), CLEAR_CHR,
           MEM_ALIGN(size + SENTRY_COUNT) - size);

    /* we rely on errno not changing. it shouldn't. */
    i_assert(errno == old_errno);
#endif
    return ret;
}

void *t_malloc_no0(size_t size)
{
    return t_malloc_real(size, TRUE);
}

void *t_malloc0(size_t size)
{
    void *mem;

    mem = t_malloc_real(size, TRUE);
    memset(mem, 0, size);
    return mem;
}

bool t_try_realloc(void *mem, size_t size)
{
    size_t debug_adjust = 0, last_alloc_size;
    unsigned char *after_last_alloc;

    if (unlikely(size == 0 || size > SSIZE_T_MAX))
        i_panic("Trying to allocate %"PRIuSIZE_T" bytes", size);
    BLOCK_CANARY_CHECK(current_block);

    last_alloc_size = current_frame_block->last_alloc_size[frame_pos];

    /* see if we're trying to grow the memory we allocated last */
    after_last_alloc = data_stack_after_last_alloc(current_block);
#ifdef DEBUG
    debug_adjust = MEM_ALIGN(sizeof(size_t));
#endif
    if (after_last_alloc - last_alloc_size + debug_adjust == mem) {
        /* yeah, see if we have space to grow */
        size_t new_alloc_size, alloc_growth;

        new_alloc_size = ALLOC_SIZE(size);
        alloc_growth = (new_alloc_size - last_alloc_size);
#ifdef DEBUG
        size_t old_raw_size; /* sorry, non-C99 users - add braces if you need them */
        old_raw_size = *(size_t *)PTR_OFFSET(mem, -(ptrdiff_t)MEM_ALIGN(sizeof(size_t)));
        i_assert(ALLOC_SIZE(old_raw_size) == last_alloc_size);
        /* Only check one byte for over-run, that catches most
           offenders who are likely to use t_try_realloc() */
        i_assert(((unsigned char*)mem)[old_raw_size] == CLEAR_CHR);
#endif

        if (current_block->left >= alloc_growth) {
            /* just shrink the available size */
            current_block->left -= alloc_growth;
            if (current_block->left < current_block->lowwater)
                current_block->lowwater = current_block->left;
            current_frame_block->last_alloc_size[frame_pos] =
                new_alloc_size;
#ifdef DEBUG
            /* All reallocs are permanent by definition
               However, they don't count as a new allocation */
            current_frame_block->alloc_bytes[frame_pos] += alloc_growth;
            *(size_t *)PTR_OFFSET(mem, -(ptrdiff_t)MEM_ALIGN(sizeof(size_t))) = size;
            memset(PTR_OFFSET(mem, size), CLEAR_CHR,
                   new_alloc_size - size - MEM_ALIGN(sizeof(size_t)));
#endif
            return TRUE;
        }
    }

    return FALSE;
}

size_t t_get_bytes_available(void)
{
#ifndef DEBUG
    const unsigned int extra = MEM_ALIGN_SIZE-1;
#else
    const unsigned int extra = MEM_ALIGN_SIZE-1 + SENTRY_COUNT +
        MEM_ALIGN(sizeof(size_t));
#endif
    BLOCK_CANARY_CHECK(current_block);
    return current_block->left < extra ? current_block->left :
        current_block->left - extra;
}

void *t_buffer_get(size_t size)
{
    void *ret;

    ret = t_malloc_real(size, FALSE);

    last_buffer_size = size;
    last_buffer_block = current_block;
    return ret;
}

void *t_buffer_reget(void *buffer, size_t size)
{
    size_t old_size;
    void *new_buffer;

    old_size = last_buffer_size;
    if (size <= old_size)
        return buffer;

    new_buffer = t_buffer_get(size);
    if (new_buffer != buffer)
        memcpy(new_buffer, buffer, old_size);

    return new_buffer;
}

void t_buffer_alloc(size_t size)
{
    i_assert(last_buffer_block != NULL);
    i_assert(last_buffer_size >= size);
    i_assert(current_block->left >= size);

    /* we've already reserved the space, now we just mark it used */
    (void)t_malloc_real(size, TRUE);
}

void t_buffer_alloc_last_full(void)
{
    if (last_buffer_block != NULL)
        (void)t_malloc_real(last_buffer_size, TRUE);
}

void data_stack_set_clean_after_pop(bool enable ATTR_UNUSED)
{
#ifndef DEBUG
    clean_after_pop = enable;
#endif
}

void data_stack_init(void)
{
    if (data_stack_initialized) {
        /* already initialized (we did auto-initialization in
           t_malloc/t_push) */
        return;
    }
    data_stack_initialized = TRUE;
    data_stack_frame = (data_stack_frame_t)1;

    outofmem_area.block.size = outofmem_area.block.left =
        sizeof(outofmem_area) - sizeof(outofmem_area.block);

    current_block = mem_block_alloc(INITIAL_STACK_SIZE);
    current_block->left = current_block->size;
    current_block->next = NULL;

    current_frame_block = NULL;
    unused_frame_blocks = NULL;
    frame_pos = BLOCK_FRAME_COUNT-1;

    last_buffer_block = NULL;
    last_buffer_size = 0;

    root_frame_id = t_push("data_stack_init");
}

void data_stack_deinit(void)
{
    if (!t_pop(&root_frame_id) ||
        frame_pos != BLOCK_FRAME_COUNT-1)
        i_panic("Missing t_pop() call");

#ifndef USE_GC
    while (unused_frame_blocks != NULL) {
        struct stack_frame_block *frame_block = unused_frame_blocks;
        unused_frame_blocks = unused_frame_blocks->prev;

        free(frame_block);
    }

    free(current_block);
    free(unused_block);
#endif
    unused_frame_blocks = NULL;
    current_block = NULL;
    unused_block = NULL;
}