Stack trace

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In computing, a stack trace (also called stack backtrace or stack traceback) is a report of the active stack frames at a certain point in time during the execution of a program.

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 function calls do not appear in a stack trace.

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

def a():
    b()
 
def b():
    c()
 
def c():
    error()
 
a()

Running the program under the standard Python interpreter produces the following error message.

Traceback (most recent call last):
  File "tb.py", line 10, in <module>
    a()
  File "tb.py", line 2, in a
    b()
  File "tb.py", line 5, in b
    c()
  File "tb.py", line 8, in c
    error()
NameError: global name 'error' is not defined

The stack trace shows where the error occurs, namely in the c function. It also shows that the c function was called by b, which was called by a, which was in turn called by the code on line 10 (the last line) of the program.

Language support[edit]

Most programming languages, including Java and C#, have built-in support for retrieving the current stack trace via system calls. C++ has no built-in support for doing this, but C++ users can retrieve stack traces with (for example) the stacktrace library.

See also[edit]