R packages that are published on CRAN are tested every night on a variety of platforms and on the development version of R to ensure that they continue to work. In addition, packages that contain compiled code (C, C++ or Fortran) are put through a raft of additional checks to ensure that the compiled code will not cause R to crash. Once an issue is found, the package maintainer gets an email and usually a fairly short window to fix the package before it is removed from CRAN.