c - 如何确定 PIC32 中的 malloc 堆统计信息

Question

我在 pic32 处理器上使用 malloc()/free() 和朋友，所以没有虚拟内存等等，只是我在链接时声明的固定大小的堆。有什么方法可以在运行时确定我目前 malloc 了多少？还有多少可用？我见过一些对 mallinfo() 函数的引用，但当前的 pic32 库似乎不支持它。

Answer 1

我已经使用了 PIC18 和 PIC24 处理器，并且发现堆要谨慎使用。malloc()一个技巧是在设备启动时，通过使用越来越大的内存块来确定堆大小，free()直到找到限制。然后，您可以自行跟踪分配的内存。

注意事项：

• 如果您分配/取消分配奇数或大块内存，所有赌注都malloc()将失败，如果您碰巧有足够的可用内存字节，但不在连续块中，则会失败。
• malloc()如果您使用使用/的第三方代码，free()您还必须查看/修改他们的代码。

我发现可以在堆上完成的任何事情都可以通过静态内存或堆栈完成，但代价是重构代码。这对你来说是一个可行的选择吗？

在electronics.stackexchange.com上查看这个相关问题

Answer 2

下面是为 Arduino 编写的内存分析器。它取自Arduino 论坛中的帖子。您将需要进行必要的修改以使其在 PIC 中正常工作。但它应该能够帮助您确定运行时的内存使用情况。

/*
 * Cut-and-pasted from www.arduino.cc playground section for determining heap and stack pointer locations.
 * http://www.arduino.cc/playground/Code/AvailableMemory
 *
 * Also taken from the Pololu thread from Paul at: http://forum.pololu.com/viewtopic.php?f=10&t=989&view=unread#p4218
 *
 * Reference figure of AVR memory areas .data, .bss, heap (all growing upwards), then stack growing downward:
 * http://www.nongnu.org/avr-libc/user-manual/malloc.html
 *
 */

extern unsigned int __data_start;
extern unsigned int __data_end;
extern unsigned int __bss_start;
extern unsigned int __bss_end;
extern unsigned int __heap_start;
//extern void *__malloc_heap_start; --> apparently already declared as char*
//extern void *__malloc_margin; --> apparently already declared as a size_t
extern void *__brkval;
// RAMEND and SP seem to be available without declaration here

int16_t ramSize=0;   // total amount of ram available for partitioning
int16_t dataSize=0;  // partition size for .data section
int16_t bssSize=0;   // partition size for .bss section
int16_t heapSize=0;  // partition size for current snapshot of the heap section
int16_t stackSize=0; // partition size for current snapshot of the stack section
int16_t freeMem1=0;  // available ram calculation #1
int16_t freeMem2=0;  // available ram calculation #2


/* This function places the current value of the heap and stack pointers in the
 * variables. You can call it from any place in your code and save the data for
 * outputting or displaying later. This allows you to check at different parts of
 * your program flow.
 * The stack pointer starts at the top of RAM and grows downwards. The heap pointer
 * starts just above the static variables etc. and grows upwards. SP should always
 * be larger than HP or you'll be in big trouble! The smaller the gap, the more
 * careful you need to be. Julian Gall 6-Feb-2009.
 */
uint8_t *heapptr, *stackptr;
uint16_t diff=0;
void check_mem() {
  stackptr = (uint8_t *)malloc(4);          // use stackptr temporarily
  heapptr = stackptr;                     // save value of heap pointer
  free(stackptr);      // free up the memory again (sets stackptr to 0)
  stackptr =  (uint8_t *)(SP);           // save value of stack pointer
}


/* Stack and heap memory collision detector from: http://forum.pololu.com/viewtopic.php?f=10&t=989&view=unread#p4218
 * (found this link and good discussion from: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1213583720%3Bstart=all )
 * The idea is that you need to subtract your current stack pointer (conveniently given by the address of a local variable)
 * from a pointer to the top of the static variable memory (__bss_end). If malloc() is being used, the top of the heap
 * (__brkval) needs to be used instead. In a simple test, this function seemed to do the job, showing memory gradually
 * being used up until, with around 29 bytes free, the program started behaving erratically.
 */
//extern int __bss_end;
//extern void *__brkval;

int get_free_memory()
{
  int free_memory;

  if((int)__brkval == 0)
     free_memory = ((int)&free_memory) - ((int)&__bss_end);
  else
    free_memory = ((int)&free_memory) - ((int)__brkval);

  return free_memory;
}


void setup()                    // run once, when the sketch starts
{
  Serial.begin(57600);
}

void loop()                     // run over and over again
{
  Serial.print("\n\n--------------------------------------------");
  Serial.print("\n\nLOOP BEGIN: get_free_memory() reports [");
  Serial.print( get_free_memory() );
  Serial.print("] (bytes) which must be > 0 for no heap/stack collision");


  Serial.print("\n\nSP should always be larger than HP or you'll be in big trouble!");

  check_mem();

  Serial.print("\nheapptr=[0x"); Serial.print( (int) heapptr, HEX); Serial.print("] (growing upward, "); Serial.print( (int) heapptr, DEC); Serial.print(" decimal)");

  Serial.print("\nstackptr=[0x"); Serial.print( (int) stackptr, HEX); Serial.print("] (growing downward, "); Serial.print( (int) stackptr, DEC); Serial.print(" decimal)");

  Serial.print("\ndifference should be positive: diff=stackptr-heapptr, diff=[0x");
  diff=stackptr-heapptr;
  Serial.print( (int) diff, HEX); Serial.print("] (which is ["); Serial.print( (int) diff, DEC); Serial.print("] (bytes decimal)");


  Serial.print("\n\nLOOP END: get_free_memory() reports [");
  Serial.print( get_free_memory() );
  Serial.print("] (bytes) which must be > 0 for no heap/stack collision");


  // ---------------- Print memory profile -----------------
  Serial.print("\n\n__data_start=[0x"); Serial.print( (int) &__data_start, HEX ); Serial.print("] which is ["); Serial.print( (int) &__data_start, DEC); Serial.print("] bytes decimal");

  Serial.print("\n__data_end=[0x"); Serial.print((int) &__data_end, HEX ); Serial.print("] which is ["); Serial.print( (int) &__data_end, DEC); Serial.print("] bytes decimal");

  Serial.print("\n__bss_start=[0x"); Serial.print((int) & __bss_start, HEX ); Serial.print("] which is ["); Serial.print( (int) &__bss_start, DEC); Serial.print("] bytes decimal");

  Serial.print("\n__bss_end=[0x"); Serial.print( (int) &__bss_end, HEX ); Serial.print("] which is ["); Serial.print( (int) &__bss_end, DEC); Serial.print("] bytes decimal");

  Serial.print("\n__heap_start=[0x"); Serial.print( (int) &__heap_start, HEX ); Serial.print("] which is ["); Serial.print( (int) &__heap_start, DEC); Serial.print("] bytes decimal");

  Serial.print("\n__malloc_heap_start=[0x"); Serial.print( (int) __malloc_heap_start, HEX ); Serial.print("] which is ["); Serial.print( (int) __malloc_heap_start, DEC); Serial.print("] bytes decimal");

  Serial.print("\n__malloc_margin=[0x"); Serial.print( (int) &__malloc_margin, HEX ); Serial.print("] which is ["); Serial.print( (int) &__malloc_margin, DEC); Serial.print("] bytes decimal");

  Serial.print("\n__brkval=[0x"); Serial.print( (int) __brkval, HEX ); Serial.print("] which is ["); Serial.print( (int) __brkval, DEC); Serial.print("] bytes decimal");

  Serial.print("\nSP=[0x"); Serial.print( (int) SP, HEX ); Serial.print("] which is ["); Serial.print( (int) SP, DEC); Serial.print("] bytes decimal");

  Serial.print("\nRAMEND=[0x"); Serial.print( (int) RAMEND, HEX ); Serial.print("] which is ["); Serial.print( (int) RAMEND, DEC); Serial.print("] bytes decimal");

  // summaries:
  ramSize   = (int) RAMEND       - (int) &__data_start;
  dataSize  = (int) &__data_end  - (int) &__data_start;
  bssSize   = (int) &__bss_end   - (int) &__bss_start;
  heapSize  = (int) __brkval     - (int) &__heap_start;
  stackSize = (int) RAMEND       - (int) SP;
  freeMem1  = (int) SP           - (int) __brkval;
  freeMem2  = ramSize - stackSize - heapSize - bssSize - dataSize;
  Serial.print("\n--- section size summaries ---");
  Serial.print("\nram   size=["); Serial.print( ramSize, DEC ); Serial.print("] bytes decimal");
  Serial.print("\n.data size=["); Serial.print( dataSize, DEC ); Serial.print("] bytes decimal");
  Serial.print("\n.bss  size=["); Serial.print( bssSize, DEC ); Serial.print("] bytes decimal");
  Serial.print("\nheap  size=["); Serial.print( heapSize, DEC ); Serial.print("] bytes decimal");
  Serial.print("\nstack size=["); Serial.print( stackSize, DEC ); Serial.print("] bytes decimal");
  Serial.print("\nfree size1=["); Serial.print( freeMem1, DEC ); Serial.print("] bytes decimal");
  Serial.print("\nfree size2=["); Serial.print( freeMem2, DEC ); Serial.print("] bytes decimal");

  delay(3000);
}

不是一个精确的解决方案，但它应该作为一个很好的起点。