Why is my bash script getting "Killed"? How do I prevent that?

I have written a bash script to test student written C programs against a test-suite. For some reason the script is getting Killed after a while. I'm a novice in bash scripting and till now has not found the reason. Here's the script.

#!/bin/bash
ulimit -t 1
tests_dir=tests
run_dir=tests
find . -name "*.c" | while read cfile; do rm a.out &> /dev/null; gcc "$cfile" -lm -w &> /dev/null;
if [ ! -f a.out ]; 
then 
    echo "$cfile did-not-compile" >> "$run_dir/results.out";
else
    find "$tests_dir" -name "in*.txt" | while read testin; do echo "running $testin on $cfile"; 
    rm test.out &> /dev/null; 
    rm space_less_testout &> /dev/null;
    LD_PRELOAD=../../EasySandbox/EasySandbox.so ./a.out < $testin | grep -v "entering SECCOMP mode" &> test.out;
    if [ -e test.out ]; then
            testout=${testin/in/out}
            tr -d '\n' < $testout | tr -d ' ' > space_less_testout
            echo -e '\n' >> space_less_testout

            if diff -qwB "$testout" test.out &> /dev/null
            then
                    # if no difference then takes true brance (based on return value)
                    echo "$cfile ;passed-on-test; $testin" >> "$run_dir/results.out"; echo "passed-on-test $testin";
            elif diff -qB space_less_testout test.out &> /dev/null 
            then
                    # or no difference with new-line removed should-be-output (just a formatting error)
                    echo "$cfile ;passed-on-test; $testin" >> "$run_dir/results.out"; echo "passed-on-test $testin";
            else
                    echo "$cfile ;failed-on-test; $testin" >> "$run_dir/results.out"; echo "failed-on-test $testin";
            fi
    fi
done;
fi
done;

ulimit -t 1 limits the script's CPU time to 1 second. When the script has consumed all its CPU time it gets killed.

To limit the CPU time of just one command in your script you can use parentheses to start it in a subshell with its own limit, e.g.

(ulimit -t 1; LD_PRELOAD=../../EasySandbox/EasySandbox.so ./a.out < $testin)