The C being generated from this for the constrained BIT STRINGs is incorrect. The unused bits look distinctly squiffy.

FooBar {1 2 3 4 5 6} DEFINITIONS ::=
  BEGIN
    Type1 ::= CHOICE {element0 INTEGER}
    value1 Type1 ::= element0:1
    Type2 ::= BIT STRING (SIZE (1..2)) (SIZE (2..2))
    value2 Type2 ::= '01'B
    Type3 ::= INTEGER
    value3 Type3 ::= 3
    Type4 ::= BIT STRING
    value4 Type4 ::= '001'B
    Type5 ::= BIT STRING (SIZE (3..6)) (SIZE (6..6)) (SIZE (6..6))
    value5 Type5 ::= '010101'B
    Type6 ::= SEQUENCE {element1 BIT STRING (SIZE (3..3)) (SIZE (3..3)) (SIZE (3..3)),
                        element2 SEQUENCE {},
                        element3 CHOICE {element4 INTEGER}}
    value6 Type6 ::= {element1 '000'B,
                      element2 {},
                      element3 element4:0}
    Type7 ::= SEQUENCE {}
    value7 Type7 ::= {}
    Type8 ::= CHOICE {element5 [0] IMPLICIT SEQUENCE {element6 [1] IMPLICIT INTEGER},
                      element7 INTEGER}
    value8 Type8 ::= element5:{element6 2}
    Type9 ::= INTEGER
    value9 Type9 ::= -2
    Type10 ::= BIT STRING
    value10 Type10 ::= '0011'B
  END

  (*type1).present = Type1_PR_element0;
  (*type1).choice.element0 = 1;
   
   
  (*type2).buf = calloc (1, 1); /* 1 bytes */
  assert((*type2).buf);
  (*type2).size = 1;
  (*type2).buf[0] = 64;
  (*type2).bits_unused = 2; /* Trim unused bits */
   
  (*type3) = 3;
   
   
  (*type4).buf = calloc (1, 1); /* 1 bytes */
  assert((*type4).buf);
  (*type4).size = 1;
  (*type4).buf[0] = 32;
  (*type4).bits_unused = 3; /* Trim unused bits */
   
   
  (*type5).buf = calloc (1, 1); /* 1 bytes */
  assert((*type5).buf);
  (*type5).size = 1;
  (*type5).buf[0] = 84;
  (*type5).bits_unused = 6; /* Trim unused bits */
   
   
  (*type6).element1.buf = calloc (1, 1); /* 1 bytes */
  assert((*type6).element1.buf);
  (*type6).element1.size = 1;
  (*type6).element1.buf[0] = 0;
  (*type6).element1.bits_unused = 3; /* Trim unused bits */
  (*type6).element3.present = element3_PR_element4;
  (*type6).element3.choice.element4 = 0;
   
   
  (*type8).present = Type8_PR_element5;
  (*type8).choice.element5.element6 = 2;
   
  (*type9) = -2;
   
   
  (*type10).buf = calloc (1, 1); /* 1 bytes */
  assert((*type10).buf);
  (*type10).size = 1;
  (*type10).buf[0] = 48;
  (*type10).bits_unused = 4; /* Trim unused bits */