/in/foo.c: In function 'main':
/in/foo.c:20:21: warning: implicit declaration of function 'isZero' [-Wimplicit-function-declaration]
   for(j=i; j<row && isZero(M[j][i]); j++)
                     ^~~~~~
/in/foo.c:22:3: warning: implicit declaration of function 'swapLine' [-Wimplicit-function-declaration]
   swapLine(i, j);
   ^~~~~~~~
/in/foo.c:33:3: error: expected ';' before '}' token
   }
   ^
/in/foo.c: At top level:
/in/foo.c:41:6: warning: conflicting types for 'swapLine'
 void swapLine(int id1, int id2){
      ^~~~~~~~
/in/foo.c:22:3: note: previous implicit declaration of 'swapLine' was here
   swapLine(i, j);
   ^~~~~~~~