add detail

Author: Vladimir Kotal

docs/class-assignments/extra-feedback.txt

@@ -12,7 +12,7 @@ Do not blindly accept potentially unlimited user input. It probably does not
 make sense for command line to be millions of characters long.
 
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-Check return values of any call that can fail.
+Check return values (and react on them !) of any call that can fail.
 
 Yes, malloc() can fail too.