Google Summer of Code | malloc_info() changes the state of the heap (#41)

[Anshika Gupta (@anshika_gupta)]

Anshika Gupta commented: https://gitlab.rtems.org/rtems/programs/gsoc/-/issues/41#note_143587


@gedare @chris 

Yuh, I could locate that call of `_Heap_Get_Information()` and could see that it is calling `_Heap_Protection_free_all_delayed_blocks()`. I rebuilt the zynqmp_qemu with` RTEMS_DEBUG = True` which **enabled the Heap_Protection** and changed my hello.c code such that I initially allocated memory and then freed it and printed the `delayed_free_block_count` which was equal to **5**. After calling malloc_info once, the **delayed_free_block_count decreased to 0** showing that malloc_info() is freeing the delayed blocks which I think recreates the issue of "malloc_info changes the state of the heap". Could you please confirm whether this counts as recreating the issue and should I start writing the proposal for this project?

My Output

```
anshikagupta at Anshikas-MacBook-Pro hello % qemu-system-aarch64 \                                                                       
  -machine xlnx-zcu102 \
  -m 1024 \
  -nographic \
  -no-reboot \
  -kernel build/aarch64-rtems7-zynqmp_qemu/hello.exe

HEAP_PROTECTION is ENABLED
delayed_free_block_count = 5
Stats after first malloc_info
Heap Information
  Free blocks      : 1
  Free largest     : 1071307712 bytes
  Free total       : 1071307712 bytes
  Used blocks      : 14
  Used largest     : 8384 bytes
  Used total       : 20640 bytes
Heap Statistics
  Lifetime alloc   : 26160 bytes
  Lifetime freed   : 5520 bytes
  Current free     : 1071307712 bytes
  Free blocks stat : 1
  Used blocks stat : 14
delayed_free_block_count = 0
Stats after second malloc info
Heap Information
  Free blocks      : 1
  Free largest     : 1071307712 bytes
  Free total       : 1071307712 bytes
  Used blocks      : 14
  Used largest     : 8384 bytes
  Used total       : 20640 bytes
Heap Statistics
  Lifetime alloc   : 26160 bytes
  Lifetime freed   : 5520 bytes
  Current free     : 1071307712 bytes
  Free blocks stat : 1
  Used blocks stat : 14
delayed_free_block_count = 0

[ RTEMS shutdown ]
RTEMS version: 7.0.0.e5eaa824202a3760d508012b13b9df45c43e670c
RTEMS tools: 15.2.0 20250808 (RTEMS 7, RSB 424f142d70c97ca4e498e58d666d798c9de4a264, Newlib 038afec1)
executing thread ID: 0x0a010001
executing thread name: UI1 
```

The hello.c code I used

```
#include <rtems/confdefs.h>
#include <rtems/malloc.h>
#include <rtems/libcsupport.h>
#include <rtems/score/heapinfo.h>
#include <rtems/score/heapimpl.h>


static void print_info(Heap_Information_block *info)
{
    printf("Heap Information\n");
    printf("  Free blocks      : %zu\n", info->Free.number);
    printf("  Free largest     : %zu bytes\n", info->Free.largest);
    printf("  Free total       : %zu bytes\n", info->Free.total);
    printf("  Used blocks      : %zu\n", info->Used.number);
    printf("  Used largest     : %zu bytes\n", info->Used.largest);
    printf("  Used total       : %zu bytes\n", info->Used.total);
    
    printf("Heap Statistics\n");
    printf("  Lifetime alloc   : %llu bytes\n",
           info->Stats.lifetime_allocated);
    printf("  Lifetime freed   : %llu bytes\n",
           info->Stats.lifetime_freed);
    printf("  Current free     : %zu bytes\n",
           info->Stats.free_size);
    printf("  Free blocks stat : %u\n",
           info->Stats.free_blocks);
    printf("  Used blocks stat : %u\n",
           info->Stats.used_blocks);
}

    
#ifdef HEAP_PROTECTION
static void print_delayed()
{
    printf("delayed_free_block_count = %d\n", RTEMS_Malloc_Heap->Protection.delayed_free_block_count);
}
#endif

    
rtems_task Init(rtems_task_argument ignored)   
{
#ifdef HEAP_PROTECTION
    printf("HEAP_PROTECTION is ENABLED\n");
#else
    printf("HEAP_PROTECTION is NOT ENABLED\n");
#endif
    
    void *ptrs[5];
    Heap_Information_block before;
    Heap_Information_block after;

    for (int i = 0; i < 5; i++) {
        ptrs[i] = malloc(1024);
    }

    for (int i = 0; i < 5; i++) {
        free(ptrs[i]);
    }

#ifdef HEAP_PROTECTION
    print_delayed();
#endif

    malloc_info(&before);
    printf("Stats after first malloc_info\n");
    print_info(&before);   
 
#ifdef HEAP_PROTECTION
    print_delayed();
#endif

    malloc_info(&after);
    printf("Stats after second malloc info\n");
    print_info(&after);

#ifdef HEAP_PROTECTION
    print_delayed();
#endif

    exit(0);
}
```

-- 
View it on GitLab: https://gitlab.rtems.org/rtems/programs/gsoc/-/issues/41#note_143587
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