malloc/calloc returns NULL despite there are still space on heap

[Hieu]

I am working on an application that allocate data dynamically at initialization, and my malloc/calloc returns NULL a lot earlier than I expected.

Using a debug macro, I determined that:

• The last memory successfully allocated is 8 bytes at 0x200021A8.
• I allocated 238 bytes for my data. Counting in overheads, the total should be +- 320 bytes.

I checked the memory map file and the heap is 2048B. I should not run out of memory yet.

HEAP                                     0x20002058   Section     2048  arm_startup_nrf51.o(HEAP)

What is going on?

I am using a nRF51 Dongle without SoftDevice. But this code is intended to be brought over to nRF51 running S110 v8 and nRF52 running the most up-to-date SoftDevice. I am a little worried about whether working with a SoftDevice will limit me even further.

Here is the macro I used for debugging:

#define DEBUG_ALLOC_MACRO(POINTER, NUM_ELEMENTS, TYPE)            \
  do                                                              \
  {                                                               \
    POINTER = (TYPE*) calloc(NUM_ELEMENTS, sizeof(TYPE));         \
    if (POINTER != NULL)                                          \
    {                                                             \
      mem_counter +=                                              \
          ((NUM_ELEMENTS * sizeof(TYPE)));                        \
    }                                                             \
    printf("%s(%d) Allocated %d x %s(%d) = %d B at 0x%p - Total %d B\n",  \
        __FILE__,                                                 \
        __LINE__,                                                 \
        NUM_ELEMENTS,                                             \
        #TYPE,                                                    \
        sizeof(TYPE),                                             \
        (NUM_ELEMENTS * sizeof(TYPE)),                            \
        POINTER,                                                  \
        mem_counter                                               \
        );                                                        \
  }                                                               \
  while (0)

And here is the log it generated.

file1.c(17) Allocated 1 x struct1(36) = 36 B at 0x20002060 - Total 36 B
file2.c(87) Allocated 8 x struct2(12) = 96 B at 0x20002088 - Total 132 B
parse_util.c(126) Allocated 4 x int16_t(2) = 8 B at 0x200020f0 - Total 140 B
parse_util.c(126) Allocated 5 x int16_t(2) = 10 B at 0x20002100 - Total 150 B
parse_util.c(126) Allocated 5 x int16_t(2) = 10 B at 0x20002110 - Total 160 B
parse_util.c(126) Allocated 1 x int16_t(2) = 2 B at 0x20002120 - Total 162 B
file2.c(100) Allocated 4 x struct3(28) = 112 B at 0x20002128 - Total 274 B
parse_util.c(90) Allocated 1 x uint8_t(1) = 1 B at 0x200021a0 - Total 275 B
parse_util.c(90) Allocated 8 x uint8_t(1) = 8 B at 0x200021a8 - Total 283 B
parse_util.c(90) Allocated 8 x uint8_t(1) = 8 B at 0x00000000 - Total 283 B

[Hieu]

@rols: I used <stdlib.h> for malloc() and calloc(). I checked arm_startup_nrf51.s and the heap size there is also 2048. Heap limits should be 2048B away from heap base which is 0x20002058.

                IF :DEF: __HEAP_SIZE
Heap_Size       EQU     __HEAP_SIZE
                ELSE
Heap_Size       EQU     2048
                ENDIF

                AREA    HEAP, NOINIT, READWRITE, ALIGN=3
__heap_base
Heap_Mem        SPACE   Heap_Size
__heap_limit

I will go into debug mode and check what you recommend asap.