On Wednesday, 23 January 2013 at 09:46:47 UTC, Don wrote:
> "There has been no error reported in TeX since 1994 or 1995"  -- Knuth, 2002.
> There were 7 bugs in TeX reported between 1982 and 1995.
> Tex has a lot more than 70 lines of code :-)

 Bugs in code don't always live on one line per bug; They can span multiple very easily. Some bugs are simply missing logic, untested cases, no default values in variables. Now if we have a while loop and you modify the index at the wrong spot you need to move it, making it have a bug spanning at least two lines.

 Some bugs are known but for the most part ignored, like memory management for very tiny programs. Many error values returned by the OS & errorno are ignored, but don't usually have any catastrophic effects.

 Some bugs are the effect of using a macro which expands. Logically it makes sense, but the macro makes it unstable at best; while an actual function wouldn't have a bug.

  #define min(a,b) ((a)>(b) ? (b) : (a))

  int a=1,b=2,c;
  c = min(a++, b++); //minimum of both a or b, and increase each once

  //will any of these pass?
  assert(c == 1);
  assert(a == 2);
  assert(b == 3);