Thread: implicit declaration of function?

Code:

warning: implicit declaration of function `malloc'
warning: implicit declaration of function `strlen'
warning: implicit declaration of function `strcpy'

I am getting these messages when I compile my files with: gcc -Wall -ansi -pedantic -O *.c.
But if I compile with just gcc *.c the program compiles fine and works fine.

the lines that cause the message are:

Code:

p=(char*)malloc(strlen(buffer)+1);
strcpy(p,buffer);

Could you tell me what is wrong and what is the right way to do it? Thanks in advance.

Thanks a lot, it is a simple thing but when you don't have much experience, it is a complex problem. I was trying to figure out for hours. I appreciate it, it compiles fine now.