mrw-cxx/mrw/stacktrace.hpp

/** @file

    $Id$

    $Date$
    $Author$

    @copy © Marc Wäckerlin
    @license LGPL, see file <a href="license.html">COPYING</a>

    $Log$
    Revision 1.5  2004/10/07 09:32:45  marc
    correction in parameter (const&)

    Revision 1.4  2004/08/28 16:21:25  marc
    mrw-c++-0.92 (mrw)
    - new file: version.cpp
    - new file header for all sources
    - work around warning in mrw::auto<T>
    - possibility to compile without log4cxx
    - work around bugs in demangle.h and libiberty.h
    - corrections in documentation
    - added simple tracing mechanism
    - more warnings
    - small corrections in Auto<>::Free and a new test for it
    - possibility to compile without stack trace

*/
#ifndef __MRW_STACKTRACE_HPP__
#define __MRW_STACKTRACE_HPP__
#include <mrw/auto.hpp>
#include <vector>
#include <map>
#include <string>
#include <memory>
#include <sys/mman.h>
#include <bfd.h>

#ifdef __REENTRANT
#warning "mrw::StackTrace is not thread safe yet!"
#warning "It should work, but is at least untested..."
#endif

namespace mrw {

  /** @defgroup StackTrace Collect and Format a Stack Trace

      Somewhere in a program, there is a fatal error, e.g. an
      unexpected exception is thrown. How is it possible to debug the
      problem in such a case? Sometimes you can start a debugger and
      trace the execution of your program. But what if it occurs only
      once a week, or if you cannot set a breakpoint, because you
      don't know where the problem is located, or because only the
      1000th run of a method causes a problem, or what if the problem
      occurs only at your customers installation?

      One way to solve these problems is to do logging, or even
      function tracing, so you can narrow down the lines of code,
      where the problem occurs. But sometimes this is not enough,
      especially with exceptions. One of the worst things with
      exceptions is, you can catch an exception somewhere, but you
      don't know where it was thrown. Here it is very handy, to be
      able to write a stacktrace to a logging device.

      For logging, I recommend log4cxx on page:
       - http://logging.apache.org/log4cxx

      These classes are for collecting a stack trace and later for
      formatting with source code file name, line number and the
      method name.

      For collecting the stack trace (the addresses):
       - either the GNU gcc compiler is required
       - or the GNU glibc library function @c backtrace

      For extracting information from an address, the ELF library is required.

      @note For all features and full operation, this class requires:
       - either a GNU glibc bases system (LINUX), or the GNU gcc compiler
       - a system with ELF binaries (LINUX, Solaris, ...)
       - debug information, compile option @c -g
       - it must be linked with @c -libery and @c -lbfd
  */
  //@{

  /** @brief store and print a stack trace of the actual position in code
      @pre #include <mrw/stacktrace.hpp>

      In the constructor, a stack trace is stored, but not yet
      evaluated. Therefore storing a stack trace is relatively
      fast. The evaluation is done when the stack trace is printed on
      a stream or converted to a string. "Evaluation" means, that the
      addresses are mapped to the correspoding symbols, the method
      names, sorce file names and line numbers are evaluated.

      @note Method StackTrace::createSymtable must be called exactely
      once, before evaluating the first stack trace.Best place is the
      first line of the @c main function.

      @note This class requires libbfd an libiberty. Debug information
      is required for compiling. You nee the compile option @c -g, or
      even better @c -ggdb3. To link, you need @c -lmrw, @c -lbfd and
      @c -liberty.

      @note The stack trace is known to work perfectly on Linux and
      Solaris both with GNU gcc compiler. But it should work with the
      GNU compiler on all systems, or wherever there is a glibc
      library.

      @note Symbol evaluation requires the ELF library and an ELF system.
      
      <h3>Technology</h3>

      On GNU glibc based systems (Linux), the stack trace is collected
      with GNU glibc's function @c backtrace(). On other systems
      (Solaris) it is collected using the GNU gcc's internal function @c
      __builtin_return_address(). With both functions, at most 50 steps
      back are collected.

      The evaluation is not done with the glibc library function @c
      backtrace_symbols(), because this function is unable to print
      the source file name and line number information. Instead of
      this, the executable binary is loaded into the memory and
      evaluated using the bdf library functions. For this the stack
      tracer needs to know how to find out which executable is
      running. It is possible to get this information automatically on
      Linux and Solaris. On other systems, I don't have this
      information, but you can either tell me, and I integrate support
      for your system (when I have time to do it), or provide the
      executable file name as an argument to @c
      mrw::StackTrace::createSymtable().

      <h3>Draw Backs</h3>

      Unfortunately it is not possible to extract the source file name
      and line number information if the executable was not compiled
      with debug option @c -g. But what's worse, it is not possible to
      ger symbolic information from libraries linked to the
      executable. Perhaps it could be possible, if I'd add a
      possibility to read and evaluate these libraries, but that's for
      a future release.

      @todo Add support to read debugging information from libraries
      that are linked to the executable.

      @todo Add support for alternative symbol evaluation using @c
      backtrace_symbols.
  */
  class StackTrace {
  public:
      //............................................................... typedefs
      typedef std::vector<void*> AddressTrace; ///< container for the adresses
      /// structure to store all evaluated information
      struct CodePos {
          CodePos(void* a, std::string fn, std::string fi, unsigned int l)
            throw(std::bad_exception):
            address(a), function(fn), file(fi), line(l) {
          }
          void* address;        ///< the address pointer
          std::string function; ///< function/method name
          std::string file;     ///< code file name
          unsigned int line;    ///< code line number
      };
      //................................................................ methods
      /// the constructor stores the actual stack trace
      StackTrace() throw(std::bad_exception);
      /// evaluates the symbol table and returns the formatted stack trace
      operator std::string() const throw(std::bad_exception);
      /** @return list of raw stack addresses */
      operator const AddressTrace&() const throw(std::bad_exception) {
        return _trace;
      }
      /// evaluate the stack trace and print it to a stream
      const StackTrace& print(std::ostream& os) const throw(std::bad_exception);
      /// evaluates and returns all information from a raw address
      static CodePos translate(void* addr) throw(std::bad_exception);
    
      /** @brief read the symbol table from the executable file

          @param fname The file name of the executable. On Linux
          and Solaris, this can be evaluated automatically, so the
          parameter is optional.

          @return @c true in case of success. If @c false is returned,
          the symbol table was not read and the evaluation cannot be
          done. Printing then only prints the raw addresses, without
          file, line nmber information and method names.

          @note This method must be executed once before a stack trace
          is printed the very first time. For storing a stack trace
          (that means for the creation of a mrw::StackTrace object) a
          call to this method is not yet needed.

          @note If this method is called more than once, the symbols
          are created only the first time, so you don't loose too much
          time.
       */
      static bool createSymtable(const std::string& fname="") throw(std::bad_exception);
    private:
      //............................................................... typedefs
      typedef std::map<bfd_vma, std::pair<bfd_vma, asection*> >
        Translator;
      //.............................................................. variables
      AddressTrace _trace;
      static std::auto_ptr<Translator> _dic;
      static std::vector<Translator::key_type> _addrs;
      static AutoBfd _bfd;
      static std::auto_ptr<asymbol*> _syms;
      //................................................................ methods
      static std::string filename() throw(std::bad_exception);
      static void buildSectionMap(bfd*, asection*, void*)
        throw(std::bad_exception);
  };

  /// evaluate a stack trace and shift it on a stream
  inline std::ostream& operator<<(std::ostream& os, const StackTrace& st)
    throw(std::bad_exception) {
    return os<<(std::string)st;
  }

  //@}
}
#endif