Stacktrace Support {#stacktrace-support}
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# Stacktrace Support
When debugging a code base and an assertion is hit, it is often useful to
have a stacktrace as part of an assertion in order for you to tell where
you are in the code to know why it is buggy.  Generating a stacktrace can
be done with [Boost Stacktrace](https://www.boost.org/doc/libs/1_81_0/doc/html/stacktrace.html),
or using the [stacktrace](https://en.cppreference.com/w/cpp/header/stacktrace) header if you are using a C++23 compatible compiler.

In order to enable stacktraces when using the `LOG4CXX_ASSERT` family of macros,
simply define `LOG4CXX_ENABLE_STACKTRACE` in your buildsystem.  If you are using a
compiler that does not support C++17 and the `__has_include` macro, Boost Stacktrace
must be installed and available on your system.  If your compiler supports the
`__has_include` macro, then it will search for Boost Stacktrace, followed by searching
for `<stacktrace>`.  Both implementations will insert an
entry into the MDC named `stacktrace` that may then be inserted into log
statements.  When using the [PatternLayout](@ref log4cxx.PatternLayout), this
may be accomplished by using the `%%X{stacktrace}` conversion pattern.

## Putting the stacktrace into the MDC

If you want a stacktrace in any part of your code(not just on assertions),
the following snippet of code may be used to insert a stacktrace into the
current MDC:

~~~{.cpp}
::log4cxx::MDC mdc_("stacktrace", LOG4CXX_EOL + boost::stacktrace::to_string(boost::stacktrace::stacktrace()));
~~~

This may be inserted at any point in your application, giving you access
to the current stacktrace in any log statement, not just in assert statements.
