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#define _GNU_SOURCE
#include <dlfcn.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

char tmpbuff[1024];
unsigned long tmppos = 0;
unsigned long tmpallocs = 0;

void *memset(void*,int,size_t);
void *memmove(void *to, const void *from, size_t size);

/*=========================================================
 *  * interception points
 *  */

static void * (*myfn_calloc)(size_t nmemb, size_t size);
static void * (*myfn_malloc)(size_t size);
static void   (*myfn_free)(void *ptr);
static void * (*myfn_realloc)(void *ptr, size_t size);
static void * (*myfn_memalign)(size_t blocksize, size_t bytes);

static void init()
{
	myfn_malloc     = dlsym(RTLD_NEXT, "malloc");
	myfn_free       = dlsym(RTLD_NEXT, "free");
	myfn_calloc     = dlsym(RTLD_NEXT, "calloc");
	myfn_realloc    = dlsym(RTLD_NEXT, "realloc");
	myfn_memalign   = dlsym(RTLD_NEXT, "memalign");

	if (!myfn_malloc || !myfn_free || !myfn_calloc || !myfn_realloc || !myfn_memalign)
	{
		fprintf(stderr, "Error in `dlsym`: %s\n", dlerror());
		exit(1);
	}
}

void *malloc(size_t size)
{
	static int initializing = 0;
	if (myfn_malloc == NULL)
	{
		if (!initializing)
		{
			initializing = 1;
			init();
			initializing = 0;

			fprintf(stdout, "jcheck: allocated %lu bytes of temp memory in %lu chunks during initialization\n", tmppos, tmpallocs);
		}
		else
		{
			if (tmppos + size < sizeof(tmpbuff))
			{
				void *retptr = tmpbuff + tmppos;
				tmppos += size;
				++tmpallocs;
				return retptr;
			}
			else
			{
				fprintf(stdout, "jcheck: too much memory requested during initialisation - increase tmpbuff size\n");
				exit(1);
			}
		}
	}

	fprintf(stderr, "chattymalloc: %d\n", size);
	void *ptr = myfn_malloc(size);
	return ptr;
}

void free(void *ptr)
{
	// something wrong if we call free before one of the allocators!
	if (myfn_malloc == NULL)
		init();
	if (ptr >= (void*) tmpbuff && ptr <= (void*)(tmpbuff + tmppos))
		fprintf(stdout, "freeing temp memory\n");
	else
		myfn_free(ptr);
}

void *realloc(void *ptr, size_t size)
{
	if (myfn_malloc == NULL)
	{
		void *nptr = malloc(size);
		if (nptr && ptr)
		{
			memmove(nptr, ptr, size);
			free(ptr);
		}
		return nptr;
	}
	void *nptr = myfn_realloc(ptr, size);
	return nptr;
}

void *calloc(size_t nmemb, size_t size)
{
	if (myfn_malloc == NULL)
	{
		void *ptr = malloc(nmemb*size);
		if (ptr)
		memset(ptr, 0, nmemb*size);
		return ptr;
	}
	void *ptr = myfn_calloc(nmemb, size);
	return ptr;
}

void *memalign(size_t blocksize, size_t bytes)
{
	void *ptr = myfn_memalign(blocksize, bytes);
	return ptr;
}