Let $F:[-1,1] \rightarrow \mathbf{R}$ be the function defined by setting $F(x):=x^2 \sin \left(\frac{1}{x^3}\right)$ when $x$ is non-zero, and $F(0):=0$. Show that $F$ is everywhere differentiable, but the deriative $F^{\prime}$ is not absolutely integrable, and so the second fundamental theorem of calculus does not apply in this case (at least if we interpret $\int_{[a, b]} F^{\prime}(x) d x$ using the absolutely convergent Lebesgue integral). See however the next exercise.