foo.c: In function 'min':
foo.c:6:2: error: 'for' loop initial declarations are only allowed in C99 mode
foo.c:6:2: note: use option -std=c99 or -std=gnu99 to compile your code
foo.c: In function 'max':
foo.c:17:2: error: 'for' loop initial declarations are only allowed in C99 mode
foo.c: In function 'BST':
foo.c:42:2: error: 'for' loop initial declarations are only allowed in C99 mode
foo.c: In function 'heap':
foo.c:39:1: warning: control reaches end of non-void function [-Wreturn-type]