Thank you for your answers!

There are examples when int(<some symbolic expression>, x=a..b) complaints, that it can't determine how a and/or b compare with symbolic constants of original expression. It suggests use of AllSolutions option, but that gives mess often (huge answer ipossible to observe and understand). So, one choose to compute indefinite integral and then substitute bounds. Doing this way, should we always manually analyse integrand to foresee discontinuities, branch cuts ets. that don't allow one to formal use antiderivatives?