Introduction

wikipedia Stack trace

In computing, a stack trace (also called stack backtrace[1] or stack traceback[2]) is a report of the active stack frames at a certain point in time during the execution of a program. When a program is run, memory is often dynamically allocated in two places：the stack and the heap. Memory is contiguously allocated on a stack but not on a heap, thus reflective of their names. Stack also refers to a programming construct, thus to differentiate it, this stack is referred to as the program's runtime stack. Technically, once a block of memory has been allocated on the stack, it cannot be easily removed as there can be other blocks of memory that were allocated before it. Each time a function is called in a program, a block of memory is allocated on top of the runtime stack called the activation record (or stack pointer.) At a high level, an activation record allocates memory for the function's parameters and local variables declared in the function.

Programmers commonly use stack tracing during interactive and post-mortem debugging. End-users may see a stack trace displayed as part of an error message, which the user can then report to a programmer.

A stack trace allows tracking the sequence of nested functions called - up to the point where the stack trace is generated. In a post-mortem scenario this extends up to the function where the failure occurred (but was not necessarily caused). Sibling calls do not appear in a stack trace.

As an example, the following Python program contains an error.