How can one grab a stack trace in C

Question

I know there s no standard C function to do this   I was wondering what are the techniques to to this on Windows and  nix    Windows XP is my most important OS to do this on right now

User · Answer

You should be using the unwind library    unw cursor t cursor  unw context t uc  unw word t ip  sp  unw getcontext  amp uc   unw init local  amp cursor   amp uc   unsigned long a 100   int ctr   0   while  unw step  amp cursor   gt  0      unw get reg  amp cursor  UNW REG IP   amp ip     unw get reg  amp cursor  UNW REG SP   amp sp     if  ctr  gt   10  break    a ctr      ip      Your approach also would work fine unless you make a call from a shared library   You can use the addr2line command on Linux to get the source function   line number of the corresponding PC

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There s backtrace    and backtrace symbols    From the man page   include  lt execinfo h gt   include  lt stdio h gt      void  callstack 128   int i  frames   backtrace callstack  128   char   strs   backtrace symbols callstack  frames   for  i   0  i  lt  frames    i        printf  quot  s n quot   strs i      free strs        One way to use this in a more convenient OOP way is to save the result of backtrace symbols   in an exception class constructor  Thus  whenever you throw that type of exception you have the stack trace  Then  just provide a function for printing it out  For example  class MyException   public std  exception        char    strs      MyException  const std  string  amp  message              int i  frames   backtrace callstack  128            strs   backtrace symbols callstack  frames              void printStackTrace             for  i   0  i  lt  frames    i                printf  quot  s n quot   strs i                      free strs                 try      throw MyException  quot Oops  quot      catch   MyException e         e printStackTrace       Ta da  Note  enabling optimization flags may make the resulting stack trace inaccurate  Ideally  one would use this capability with debug flags on and optimization flags off

User · Answer

For Windows check the StackWalk64   API  also on 32bit Windows   For UNIX you should use the OS  native way to do it  or fallback to glibc s backtrace    if availabe   Note however that taking a Stacktrace in native code is rarely a good idea - not because it is not possible  but because you re usally trying to achieve the wrong thing   Most of the time people try to get a stacktrace in  say  an exceptional circumstance  like when an exception is caught  an assert fails or - worst and most wrong of them all - when you get a fatal  exception  or signal like a segmentation violation   Considering the last issue  most of the APIs will require you to explicitly allocate memory or may do it internally  Doing so in the fragile state in which your program may be currently in  may acutally make things even worse   For example  the crash report  or coredump  will not reflect the actual cause of the problem  but your failed attempt to handle it    I assume you re trying to achive that fatal-error-handling thing  as most people seem to try that when it comes to getting a stacktrace   If so  I would rely on the debugger  during development  and letting the process coredump in production  or mini-dump on windows    Together with proper symbol-management  you should have no trouble figuring the causing instruction post-mortem

User · Answer

There is no platform independent way to do it    The nearest thing you can do is to run the code without optimizations  That way you can attach to the process  using the visual c   debugger or GDB  and get a usable stack trace

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For Windows  CaptureStackBackTrace   is also an option  which requires less preparation code on the user s end than StackWalk64   does    Also  for a similar scenario I had  CaptureStackBackTrace   ended up working better  more reliably  than StackWalk64

User · Answer

glibc provides backtrace   function  http   www gnu org software libc manual html node Backtraces html

User · Answer

You can do it by walking the stack backwards   In reality  though  it s frequently easier to add an identifier onto a call stack at the beginning of each function and pop it at the end  then just walk that printing the contents   It s a bit of a PITA  but it works well and will save you time in the end

User · Answer

For the past few years I have been using Ian Lance Taylor s libbacktrace  It is much cleaner than the functions in the GNU C library which require exporting all the symbols  It provides more utility for the generation of backtraces than libunwind  And last but not least  it is not defeated by ASLR as are approaches requiring external tools such as addr2line   Libbacktrace was initially part of the GCC distribution  but it is now made available by the author as a standalone library under a BSD license   https   github com ianlancetaylor libbacktrace  At the time of writing  I would not use anything else unless I need to generate backtraces on a platform which is not supported by libbacktrace

User · Answer

Solaris has the pstack command  which was also copied into Linux

[c] How can one grab a stack trace in C?

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