tree 49551a8734ebb708215487bfa2f194ed3e317430
parent ba00f67d2f5f92cd95c8beefe3085f7335ef3c62
author qining <qining@google.com> 1460416337 -0400
committer qining <qining@google.com> 1461765957 -0400

Fix the infinite loop when an input file lacks EOF

The input scanner can be trapped in an infinite loop if the given input
file does not have EOF (and is not ended with a 'whitespace').

The problem is caused by unget(), which keeps rolling back the scanner
pointer without hitting an EOF at the end of the file. This makes getch()
function keep returning the last character of the file and never ends,
and the effect of advance() is always counteracted by unget().