Makefile: Error1

I have a very simple c programme:

int main()
{
  return(1);
}

and a simple Makefile:

all:
    gcc -ansi -pedantic -o tmp tmp.c
    ./tmp

However, when I type make I get the following error message:

$ make
gcc -ansi -pedantic -o tmp tmp.c
./tmp
make: *** [all] Error 1

What obvious thing am I missing?