problem with data in allocated memory

hi,

i have a problem in storing the data in allocated memory using malloc.

i have structure to store huge data form the serial port.

Code:

typedef struct FileData {		
		unsigned char  *FRdata;
		struct FileData *next;
}FileData;

/*I store the data in FileData->FRdata, by allocating sufficient memory to it*/

Datacur->FRdata=(char *)malloc(sizeof(max_bytes));

for(j=0;bytes_to_read>0;j++,bytes_to_read--)
	Datacur->FRdata[j]=*Ftemp++;
Datacur->next=NULL;

i have to write the raw data from the serial port in to file after converting the raw into its format[ the data format is usually float type].

when i print few data before opening a file

Code:

j=0;
printf("read");
while(j<10){
printf("%02x ",Datahead->FRdata[j++]);
}

there is no change in the data .

The problem is after , file is opened

Code:

 fptr=fopen(Surveyname,"wt");

the data in the allocated memory{Datahead->FRdata[} has changed { the data that is written to file is different to that of original data.}

where cud be the malicious alteration hapened.

any help on this.

where cud be the malicious alteration hapened.

In what way is it different?

By the way, there is no need to cast the return value of malloc() in C.

Code:

Datacur->FRdata=(char *)malloc(sizeof(max_bytes));

You probably don't want a sizeof in there. You probably want just:

Code:

Datacur->FRdata = malloc(max_bytes);

How silly i was !!!!!! Thanks iMalc for rightly pointing it out......

problem got fixed!!