foo.c: In function 'main':
foo.c:4:2: error: 'v' undeclared (first use in this function)
    4 | {v=4/3*pl*r*r*r
      |  ^
foo.c:4:2: note: each undeclared identifier is reported only once for each function it appears in
foo.c:4:8: error: 'pl' undeclared (first use in this function)
    4 | {v=4/3*pl*r*r*r
      |        ^~
foo.c:4:11: error: 'r' undeclared (first use in this function)
    4 | {v=4/3*pl*r*r*r
      |           ^
foo.c:4:16: error: expected ';' before 'printf'
    4 | {v=4/3*pl*r*r*r
      |                ^
      |                ;
    5 |     printf("hello, world\n");
      |     ~~~~~~      

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