Time Regions and E ects for Resource Usage Analysis

Various resources such as les and memory are associated with certain protocols about how they should be accessed. For example, a memory cell that has been allocated should be eventually deallocated, and after the deallocation, the cell should no longer be accessed. Igarashi and Kobayashi recently proposed a general type-based method to check whether a program follows such resource access policies, but their analysis was not precise enough for certain programs. In this paper, we re ne their type-based analysis by introducing a new notion of time regions. The resulting analysis combines the merits of two major previous approaches to type-based analysis of resource usage { linear-type-based and e ect-based approaches.