Added mi_visit_blocks to visit all blocks of all heaps in a thread

[DV-AG]

Added a method "mi_visit_blocks()" in src/heap.c to visit all blocks of all heaps in a thread and made required changes in include/mimalloc.h by adding

mi_decl_export bool mi_visit_blocks(const mi_heap_t* heap ,bool visit_blocks, mi_block_visit_fun* visitor, void* arg);

Below is the function I added

bool mi_visit_blocks(const mi_heap_t* heap, bool visit_blocks, mi_block_visit_fun* visitor, void* arg) {
  mi_assert_internal(heap != NULL);
  if (heap == NULL) return false;
  mi_heap_t* curr = heap->tld->heaps;
  while (curr != NULL) {
    mi_heap_t* next = curr->next;
    if(!mi_heap_visit_blocks(curr, visit_blocks, visitor, arg)){
      return false;
    }
    curr = next;
  }
  return true;
}

This function was tested with the below code

#include <stdio.h>
#include <stdlib.h>
#include "mimalloc.h"

static int block_count = 0;


bool visit_block(const mi_heap_t* heap,
                 const mi_heap_area_t* area,
                 void* block,
                 size_t block_size,
                 void* arg)
{
    block_count++;
    printf("Visited block %p size=%zu\n", block, block_size);
    return true;   // continue visiting
}

int main() {

    
    mi_heap_t* heap = mi_heap_new();

    if (heap == NULL) {
        printf("heap creation failed\n");
        return 1;
    }

    
    void* p1 = mi_heap_malloc(heap, 64);
    void* p2 = mi_heap_malloc(heap, 128);
    void* p3 = mi_heap_malloc(heap, 256);

    printf("Allocated blocks: %p %p %p\n", p1, p2, p3);

   
    mi_visit_blocks(heap, true, visit_block, NULL);

    printf("Total blocks visited: %d\n", block_count);

    /* cleanup */
    mi_free(p1);
    mi_free(p2);
    mi_free(p3);

    mi_heap_destroy(heap);

    return 0;
}

[DV-AG]

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[DV-AG]

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[DV-AG]

Fixes #1180

[DV-AG]

Hi @daanx ,

I added mi_visit_blocks to iterate through all blocks across heaps in a thread.
Could you please review this when you have time? I'd appreciate any feedback.

Thanks!

[daanx]

Hi @DV-AG, thank you for the PR and apologies for the late reply!

• Can you resubmit the PR against the dev branch?
• The heap parameter seems not needed; can you call the function mi_thread_visit_blocks instead without the heap parameter (and use mi_heap_get_default() to get the tld heaps list)
• in v3 there are now first-class heaps and the v1,v2 mi_heap_t is now mi_theap_t; maybe we need to revise the api for those cases as well. Also, even if you visit all blocks in all threads, you still need to visit the abandoned blocks.
  Just some thoughts, Thanks!