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Pass-By-Reference

• inout mode

• Pass an access path

• Also called pass-by-sharing

• Advantage: passing process is efficient

• Disadvantages:
  • Slower accesses
  • Can allow aliasing:
    • Actual parameter collisions: sub1(x, x);
    • Array element collisions: sub1(a[i], a[j]); /* if i = j */
    • Collision between formals and globals

• Root cause of all of these is: The called subprogram is provided wider access to nonlocals than is necessary

• Pass-by-value-result does not allow these aliases (but has other problems!)