Spring Boot引起的“堆外内存泄漏”排查及经验总结

Spring Boot引起的“堆外内存泄漏”排查及经验总结

#include<sys/mman.h>
#include<stdlib.h>
#include<string.h>
#include<stdio.h>
//作者使用的64位机器，sizeof(size_t)也就是sizeof(long) 
void* malloc ( size_t size )
{
   long* ptr = mmap( 0, size + sizeof(long), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0 );
   if (ptr == MAP_FAILED) {
  	return NULL;
   }
   *ptr = size;                     // First 8 bytes contain length.
   return (void*)(&ptr[1]);        // Memory that is after length variable
}

void *calloc(size_t n, size_t size) {
 void* ptr = malloc(n * size);
 if (ptr == NULL) {
	return NULL;
 }
 memset(ptr, 0, n * size);
 return ptr;
}
void *realloc(void *ptr, size_t size)
{
 if (size == 0) {
	free(ptr);
	return NULL;
 }
 if (ptr == NULL) {
	return malloc(size);
 }
 long *plen = (long*)ptr;
 plen--;                          // Reach top of memory
 long len = *plen;
 if (size <= len) {
	return ptr;
 }
 void* rptr = malloc(size);
 if (rptr == NULL) {
	free(ptr);
	return NULL;
 }
 rptr = memcpy(rptr, ptr, len);
 free(ptr);
 return rptr;
}

void free (void* ptr )
{
   if (ptr == NULL) {
	 return;
   }
   long *plen = (long*)ptr;
   plen--;                          // Reach top of memory
   long len = *plen;               // Read length
   munmap((void*)plen, len + sizeof(long));
}