% clang -emit-llvm -c -g -O0 -Xclang -disable-O0-optnone -I /tmp/klee_src/include/klee/ TGIF_KLEE1.c

% time klee --libc=uclibc --optimize --use-query-log=solver:smt2 TGIF_KLEE1.bc

...
KLEE: ERROR: TGIF_KLEE1.c:20: failed external call: klee_assert
KLEE: NOTE: now ignoring this error at this location

KLEE: done: total instructions = 11734
KLEE: done: completed paths = 1
KLEE: done: partially completed paths = 1
KLEE: done: generated tests = 2
...

% ls klee-last/*
klee-last/assembly.ll   klee-last/run.stats                klee-last/test000001.ktest
klee-last/info          klee-last/solver-queries.smt2      klee-last/test000002.ktest
klee-last/messages.txt  klee-last/test000001.external.err  klee-last/warnings.txt
klee-last/run.istats    klee-last/test000001.kquery

% ktest-tool klee-last/test000001.ktest | grep uint
object 0: uint: 86400

% ktest-tool klee-last/test000002.ktest | grep uint
object 0: uint: 0