Question

char purl[1024];
unsigned char * puMember;
unsigned char uMember;
puMember = &uMember;

unsigned char * pMember;
unsigned char Member;
pMember = &Member;

printf("member: %s\n",pMember);
printf("username :%s\n",puMember);
sprintf(purl, "Username: %s %s",puMember,pMember);
printf("URL:%s\n",purl);
printf("member: %s\n",puMember);
printf("username :%s\n",pMember);

Output

member: 12345678
username :User1
URL: username: cUser1 ser1
member: User1
username :ser1

Im confused into why sprintf is messing up my pointers once its been executed.

pMember has 12345678 and puMember has User1, im trying to format the them into a string (purl) but it seems that sprintf is messing them up :/

Any help how i could accomplish this?

Answer 1

Your code is very strange – if pMember and puMember point to single chars, why printf them as a mull-terminated string? It will print anything until it finds a null in memory.

Likewise, sprintf will keep reading memory after the Member and uMember chars and fill up purl – depending on when it finds a null byte in memory.

Using snprintf instead of printf will avoid the buffer overrun, but what are you trying to accomplish exactly?