Print a stacktrace on Linux with GNU libc

gnu-libc-print-stacktrace.c

// this code fragment shows how to print a stack trace (to stderr)
// on Linux using the functions provided by the GNU libc

#include <execinfo.h>

#define MAX_STACK_LEVELS 50

// helper-function to print the current stack trace
void print_stacktrace()
{
  void *buffer[MAX_STACK_LEVELS];
  int levels = backtrace(buffer, MAX_STACK_LEVELS);

  // print to stderr (fd = 2), and remove this function from the trace
  backtrace_symbols_fd(buffer + 1, levels - 1, 2);
}

The constant definition should be as follows:
#define MAX_STACK_LEVELS 50

Oops. Of course. How did that get in there?