SealDebug.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/

 
 
#include "CxxUtils/SealCommon.h"               // wlav
#include "CxxUtils/SealDebug.h"                // wlav
#include "CxxUtils/SealSignal.h"               // wlav
#include "CxxUtils/UnwindBacktrace.h"          // sss
#include "CxxUtils/checker_macros.h"
 
// wlav copied from SealBase/sysapi/DebugAids.h
#include <cstring>
# include <cctype>
# include <cstdio>
# include <cstdlib>
# include <iostream>
# include <iomanip>
# include <sstream>                            // wlav
# include <climits>                            // wlav
 
# ifdef _WIN32
#  include <windows.h>
#  include <winnt.h>
#  include <imagehlp.h>
//#  include <io.h>
# else
#  include <unistd.h>
#  include <sys/wait.h>
#  include <sys/resource.h>         // fwinkl
#  if HAVE_BACKTRACE_SYMBOLS_FD     // GNU
#   include <execinfo.h>
#   include <sys/uio.h>
#   include <cxxabi.h>
#  endif
#  if HAVE_DLADDR           // Linux, Solaris
#   include <dlfcn.h>
#  endif
# if HAVE_EXCEPTION_H
    // This is yucky.  KCC's <exception.h> that has nothing to do with the
    // header we are looking for (it redirect to <exception>).  This ugly
    // workaround allows us to find the (IRIX) header we are looking for.
#   if defined __KCC && defined __sgi
#     include </usr/include/exception.h>
#    elif defined __sgi
#     include <exception.h>
#    endif
#  endif
#  if HAVE_EXCPT_H          // IRIX
#   include <excpt.h>
#   undef try     // Defined on SGI to structured exception handling goop
#   undef catch   // Defined on SGI to structured exception handling goop
#  endif
#  if HAVE_RLD_INTERFACE_H      // Tru64 (IRIX)
#   include <rld_interface.h>
#  endif
#  if HAVE_PDSC_H           // Tru64
#   include <pdsc.h>
#  endif
#  if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) // GCC 3.4+ C++ ABI
#   include <sys/uio.h>
#  endif
# endif
 
// Windows doesn't have this, so fake a suitable substitute
# ifdef _WIN32
#  define STDERR_HANDLE GetStdHandle (STD_ERROR_HANDLE)
# else
#  define STDERR_HANDLE STDERR_FILENO
# endif
 
// Define a suitable wrapper to write to system file descriptors.
// This is needed because on Windows we are using HANDLEs, not the
// compiler's crippled posixy interface.
# ifdef _WIN32
#  define MYWRITE(fd,data,n)    do { DWORD written; WriteFile(fd,data,n,\
                    &written,0); } while (0)
# else
#  define MYWRITE(fd,data,n)    write(fd,data,n)
# endif
 
// Helper to write literals
# define MYWRITELIT(fd,str) MYWRITE(fd,str,sizeof(str)-1)
 
//<<<<<< PUBLIC CONSTANTS                                               >>>>>>
//<<<<<< PUBLIC TYPES                                                   >>>>>>
//<<<<<< PUBLIC VARIABLES                                               >>>>>>
 
#if HAVE_BACKTRACE_SYMBOLS_FD
static const int MAX_BACKTRACE_DEPTH = 128;
#endif
 
 
#if HAVE_BACKTRACE_SYMBOLS_FD && HAVE_DLADDR
// sss
#include <unistd.h>
#include <errno.h>
namespace {
 
 
std::string addr2LinePath = "/usr/bin/eu-addr2line";
 
 
struct ATLAS_NOT_THREAD_SAFE BacktraceInit
{
  BacktraceInit()
  {
    // backtrace() has a one-time initialization that uses malloc().
    // so call it once now.
    void* trace[1];
    backtrace (trace, 1);
 
    if (access (addr2LinePath.c_str(), F_OK) == 0) {
      return;
    }
 
    // Search PATH for addr2line / eu-addr2line.
    std::string path = getenv ("PATH");
    while (!path.empty()) {
      std::string::size_type pos = path.find (':');
      std::string dir = path.substr (0, pos);
      if (pos != std::string::npos) ++pos;
      path.erase (0, pos);
 
      {
        std::string p1 = dir + "/eu-addr2line";
        if (access (p1.c_str(), F_OK) == 0) {
          addr2LinePath = std::move (p1);
          break;
        }
      }
 
      {
        std::string p2 = dir + "/addr2line";
        if (access (p2.c_str(), F_OK) == 0) {
          addr2LinePath = std::move (p2);
          break;
        }
      }
    }
  }
};
BacktraceInit backtraceInit;
 
 
// This is like popen, except that it returns a fd rather
// than a FILE*.  The PID is returned in pid.
// This is to avoid memory allocation.
int stacktracePopenFD (const char* cmd, pid_t& child_pid)
{
  int stat;
  int fds[2];
 
  // The glibc popen() uses pipe2() here with O_CLOEXEC.
  // pipe2() is linux-specific, though, so avoid it here.
  stat = pipe (fds);
  if (stat < 0) return stat;
 
  int parent_end = fds[0];
  int child_end = fds[1];
 
#ifdef __linux__
  // Use vfork rather than fork to avoid running pthread_atfork handlers.
  // Openblas, for example, registers one unconditionally, but that can
  // segfault if called with the program in a bad state.
  // What we're doing here doesn't really comply with the restrictions
  // in the vfork man page, which says that in the child after the vfork
  // you can do only exec or _exit.  This does in fact seem to work
  // on linux, but put this within an ifdef.
  child_pid = vfork();
#else
  child_pid = fork();
#endif
  if (child_pid == 0) {
    int child_std_end = 1;
    close (parent_end);
    if (child_end != child_std_end) {
      dup2 (child_end, child_std_end);
      close (child_end);
    }
 
    /* POSIX.2:  "popen() shall ensure that any streams from previous
       popen() calls that remain open in the parent process are closed
       in the new child process."
 
       For our specific case here, we ignore this. */
    
    execl ("/bin/sh", "sh", "-c", cmd, (char *) 0);
    _exit (127);
  }
 
  close (child_end);
  if (child_pid < 0) {
    close (parent_end);
    return child_pid;
  }
 
  return parent_end;
}
 
 
int stacktracePcloseFD (int fd, pid_t child_pid)
{
  int stat = close (fd);
  if (stat < 0) return stat;
 
  /* POSIX.2 Rationale:  "Some historical implementations either block
     or ignore the signals SIGINT, SIGQUIT, and SIGHUP while waiting
     for the child process to terminate.  Since this behavior is not
     described in POSIX.2, such implementations are not conforming." */
  pid_t wait_pid;
  int wstatus;
  do {
    wait_pid = waitpid (child_pid, &wstatus, 0);
  } while (wait_pid == -1 && errno == EINTR);
 
  if (wait_pid == -1)
    return -1;
  return wstatus;
}
 
 
int stacktraceReadline (int fd, char* buf, int buflen)
{
  int len = 0;
  while (len < buflen-1) {
    int stat = read (fd, buf, 1);
    if (stat < 0) return stat;
    if (stat == 0) break;
    if (*buf == '\n') break;
    ++len;
    ++buf;
  }
  *buf = '\0';
  return len;
}
 
 
} // anonymous namespace
// sss
#endif
 
 
namespace Athena {                             // wlav
 

std::atomic<IOFD>  DebugAids::s_stackTraceFd = IOFD_INVALID;
 
 
#ifdef _WIN32
// /** WIN32 function to grab the current PC address from the SEH context.
//     We need this to grab the exception context so we can walk the stack
//     in #Debug::stacktrace().  We use SEH (as compiler-independently as
//     we can) as only XP 64-bit has RtlGetContext() function.  */
// static LONG CALLBACK
// GrabExceptionContext (PEXCEPTION_POINTERS info)
// {
//     *((CONTEXT *) info->ExceptionRecord->ExceptionInformation[0])
//  = *info->ContextRecord;
//     return EXCEPTION_EXECUTE_HANDLER;
// }

bool
GetLogicalAddress (PVOID addr, PTSTR name, DWORD length,
           DWORD &section, DWORD &offset)
{
    MEMORY_BASIC_INFORMATION info;
 
    if (! VirtualQuery (addr, &info, sizeof (info)))
    return false;
 
    DWORD module = (DWORD) info.AllocationBase;
    if (! GetModuleFileName ((HMODULE) module, name, length))
    return false;
 
    PIMAGE_DOS_HEADER       dosheader = (PIMAGE_DOS_HEADER) module;
    PIMAGE_NT_HEADERS       ntheader
    = (PIMAGE_NT_HEADERS) (module + dosheader->e_lfanew);
    PIMAGE_SECTION_HEADER   sect = IMAGE_FIRST_SECTION (ntheader);
    DWORD           rva = (DWORD) addr - module;
 
    for (unsigned i = 0; i < ntheader->FileHeader.NumberOfSections; ++i,++sect)
    {
    DWORD sect_start = sect->VirtualAddress;
    DWORD sect_end = sect_start + std::max (sect->SizeOfRawData,
                            sect->Misc.VirtualSize);
 
    if ((rva >= sect_start) && (rva <= sect_end))
    {
        section = i+1;
        offset = rva - sect_start;
        return true;
    }
    }
 
    assert (false);
    return false;
}
#endif

void DebugAids::stacktraceLine ATLAS_NOT_THREAD_SAFE (IOFD fd,
                                                      unsigned long addr)
{
  iovec     bufs [7];
  int       nbufs = 0;
  const int     addrbuf_size = 5 + BitTraits<unsigned long>::HexDigits;
  char      addrbuf [addrbuf_size];
 
#if HAVE_BACKTRACE_SYMBOLS_FD && HAVE_DLADDR
  const int     diffbuf_size = 15 + BitTraits<unsigned long>::HexDigits;
  char      diffbuf [diffbuf_size];
  static const char trailer [] = "]\n";
  Dl_info       info;
 
  char dembuf[ LINE_MAX ];
  char line[ LINE_MAX ];
  const int     relbuf_size = 7 + BitTraits<unsigned long>::HexDigits;
  char    relbuf [relbuf_size];
 
  if (dladdr ((void*)addr, &info) && info.dli_fname && info.dli_fname[0])
  {
    const char *libname = info.dli_fname;
           
    unsigned long   symaddr = (unsigned long) info.dli_saddr;
    bool        gte = (addr >= symaddr);
    unsigned long   diff = (gte ? addr - symaddr : symaddr - addr);
 
    // RS start
    int length = 0;
    
    // difference of two pointers
    unsigned long libaddr = (unsigned long) info.dli_fbase;
    unsigned long relative_address = (addr >= libaddr) ? addr - libaddr : libaddr - addr;
    // ELF executables are usually not relocatable, and on 64-bit platforms
    // are usually loaded starting at 0x400000.  In that case, we should _not_
    // subtract the base address.  But clang15 by default appears to produce
    // position-independent executables (PIE) by default.  In that case,
    // we do need to subtract the offset.
    // I'm not sure how to reliably tell the difference short of parsing
    // the object headers.  For now, just assume that something
    // that doesn't have .so in the name and is loaded at 0x400000
    // is not relocatable.  This is not really portable, though.
    if (strstr (info.dli_fname, ".so") == 0 && libaddr == 0x400000)
      relative_address = addr;
 
    // need popen for addr2line ...
    int pfd;
    pid_t child_pid;
    const char* symname = dembuf;
    size_t demlen = 0;
 
    // did we find valid entry ?
    size_t len = strlen(info.dli_fname);
    if ( len > 0 && len + 80 < LINE_MAX)
    {
      if (getenv ("LD_PRELOAD"))
        unsetenv ("LD_PRELOAD");
 
      if ( addr2LinePath == "/usr/bin/eu-addr2line" )
    {
      snprintf (line, LINE_MAX, "%s -f -e %s %p | /usr/bin/c++filt | /usr/bin/tr \\\\012 \\\\040 ",
            addr2LinePath.c_str(),
            info.dli_fname,
            (void*)relative_address); 
    }
      else
    {
      snprintf (line, LINE_MAX, "%s -f -C -e %s %p",
            addr2LinePath.c_str(),
            info.dli_fname,
            (void*)relative_address);
    }
 
      pfd = stacktracePopenFD( line, child_pid );
 
      length = 1;
      line[0] = ' ';
 
      // did we succeed to open the pipe?
      if ( pfd >= 0 )
      {
        demlen = stacktraceReadline (pfd, dembuf, sizeof(dembuf));
 
        length = stacktraceReadline (pfd, line+1, sizeof(line)-1);
        if (length >= 0) ++length;
 
        int stat = stacktracePcloseFD (pfd, child_pid);
 
        // don't print anything, if nothing is found
        if ( stat || line[1] == '?' || length < 0)
        {
          line[1] = '\0';
          length = 0;
        }
 
    if ( stat || demlen <= 0 || dembuf[0] == '?') {
          symname = info.dli_sname;
          if (!symname) symname = "???";
          demlen = strlen (symname);
        }
 
      }
    }
    // RS end
 
    bufs [nbufs].iov_base = addrbuf;
    bufs [nbufs].iov_len  = snprintf (addrbuf, addrbuf_size, " 0x%08lx ", addr);
    ++nbufs;
 
    bufs [nbufs].iov_base = (void *) symname; // discard const
    bufs [nbufs].iov_len  = demlen;
    ++nbufs;
 
    // RS start
    bufs [nbufs].iov_base = line;
    bufs [nbufs].iov_len  = length;
    ++nbufs;
    // RS end
 
    bufs [nbufs].iov_base = diffbuf;
    bufs [nbufs].iov_len  = snprintf (diffbuf, diffbuf_size, " %c 0x%lx [",
                                      gte ? '+' : '-', diff);
    ++nbufs;
 
    bufs [nbufs].iov_base = (void *) libname; // discard const
    bufs [nbufs].iov_len  = strlen (libname);
    ++nbufs;
 
    // RS start
    bufs [nbufs].iov_base = relbuf;
    bufs [nbufs].iov_len  = snprintf( relbuf, relbuf_size, " D[%p]", (void*)relative_address );
    ++nbufs;
    // RS end
 
    bufs [nbufs].iov_base = (void *) trailer; // discard const
    bufs [nbufs].iov_len  = 2;
    ++nbufs;
 
  }
  else
#endif
  {
    bufs [nbufs].iov_base = addrbuf;
    bufs [nbufs].iov_len  = snprintf (addrbuf, addrbuf_size, " 0x%08lx ", addr);
    ++nbufs;
    
    bufs [nbufs].iov_base = (void *) "<unknown function>\n"; //no const
    bufs [nbufs].iov_len  = 19;
    ++nbufs;
  }
 
  writev (fd, bufs, nbufs);
}
 
 
#if !(HAVE_BACKTRACE_SYMBOLS_FD && HAVE_DLADDR) && __GNUC__ >=4 
extern "C" {
    typedef unsigned _Unwind_Ptr __attribute__((__mode__(__pointer__)));
    struct _Unwind_Context;
    typedef enum
    {
      _URC_NO_REASON = 0,
      _URC_FOREIGN_EXCEPTION_CAUGHT = 1,
      _URC_FATAL_PHASE2_ERROR = 2,
      _URC_FATAL_PHASE1_ERROR = 3,
      _URC_NORMAL_STOP = 4,
      _URC_END_OF_STACK = 5,
      _URC_HANDLER_FOUND = 6,
      _URC_INSTALL_CONTEXT = 7,
      _URC_CONTINUE_UNWIND = 8
    } _Unwind_Reason_Code;
    typedef _Unwind_Reason_Code (*_Unwind_Trace_Fn) (_Unwind_Context *, void *);
    extern _Unwind_Reason_Code _Unwind_Backtrace (_Unwind_Trace_Fn, void *);
    extern _Unwind_Ptr _Unwind_GetIP (_Unwind_Context *);
    extern _Unwind_Ptr _Unwind_GetRegionStart (_Unwind_Context *);
}

_Unwind_Reason_Code
unwindWalkStack (_Unwind_Context *ctx, void *data)
{
    IOFD        fd = *(IOFD *) data;
    iovec       bufs [5];
    int         nbufs = 0;
    const int       addrbuf_size = 5 + BitTraits<unsigned long>::HexDigits;
    char        addrbuf [addrbuf_size];
    const int       diffbuf_size = 10 + 2 * BitTraits<unsigned long>::HexDigits;
    char        diffbuf [diffbuf_size];
    static const char   trailer [] = "]\n";
    unsigned long   ip = _Unwind_GetIP (ctx);
    unsigned long   ir = _Unwind_GetRegionStart (ctx);
 
# if HAVE_DLADDR
    Dl_info     info;
    if (dladdr ((void *) ir, &info) && info.dli_fname && info.dli_fname[0])
    {
    const char  *libname = info.dli_fname;
    const char  *symname = (info.dli_sname && info.dli_sname[0]
                    ? info.dli_sname : "?");
    unsigned long   symaddr = (unsigned long) info.dli_saddr;
    bool        gte = (ip >= symaddr);
    unsigned long   diff = (gte ? ip - symaddr : symaddr - ip);
 
    bufs [nbufs].iov_base = addrbuf;
    bufs [nbufs].iov_len  = snprintf (addrbuf, addrbuf_size, " 0x%08lx ", ip);
    ++nbufs;
 
    bufs [nbufs].iov_base = (char *) symname; // discard const
    bufs [nbufs].iov_len  = strlen (symname);
    ++nbufs;
 
    bufs [nbufs].iov_base = diffbuf;
    bufs [nbufs].iov_len  = snprintf (diffbuf, diffbuf_size, " %s 0x%lx [",
                      gte ? "+" : "-", diff);
    ++nbufs;
 
    bufs [nbufs].iov_base = (char *) libname; // discard const
    bufs [nbufs].iov_len  = strlen (libname);
    ++nbufs;
 
    bufs [nbufs].iov_base = (char *) trailer; // discard const
    bufs [nbufs].iov_len  = 2;
    ++nbufs;
    }
    else
# endif // HAVE_DLADDR
    {
    bufs [nbufs].iov_base = addrbuf;
    bufs [nbufs].iov_len  = snprintf (addrbuf, addrbuf_size, " 0x%08lx ", ip);
    ++nbufs;
 
    bufs [nbufs].iov_base = diffbuf;
    bufs [nbufs].iov_len  = snprintf (diffbuf, diffbuf_size, " <?%08lx> + 0x%lx\n",
                      ir, ip - ir);
        ++nbufs;
    }
 
    writev (fd, bufs, nbufs);
    return _URC_NO_REASON;
}
#endif // GCC 3.4+
 
//<<<<<< PUBLIC FUNCTION DEFINITIONS                                    >>>>>>
 
// Change the path of the binary used for symbolization.
void DebugAids::setStackTraceAddr2Line ATLAS_NOT_THREAD_SAFE (const char* path)
{
  addr2LinePath = path;
}
 
 
#if HAVE_U_STACK_TRACE
// HP-UX stack walker (http://devresource.hp.com/STK/partner/unwind.pdf)
extern "C" void U_STACK_TRACE (void);
#endif
 
#if HAVE_XL_TRBK
// AIX stack walker (from xlf FORTRAN 90 runtime).
extern "C" void xl__trbk (void);
#endif
 
//<<<<<< MEMBER FUNCTION DEFINITIONS                                    >>>>>>

IOFD
DebugAids::stacktraceFd (IOFD fd /* = IOFD_INVALID */)
{
  IOFD old = s_stackTraceFd;
  if (fd == IOFD_INVALID) {
    if (old == IOFD_INVALID) {
      s_stackTraceFd.compare_exchange_strong (old, STDERR_HANDLE);
      return s_stackTraceFd;
    }
  }
  else {
    s_stackTraceFd.compare_exchange_strong (old, fd);
  }
  return old;
}

void
DebugAids::stacktrace ATLAS_NOT_THREAD_SAFE (IOFD fd /* = IOFD_INVALID */)
{
    if (fd == IOFD_INVALID)
      fd = stacktraceFd();
 
    std::cerr.flush ();
    fflush (stderr);
 
#ifdef _WIN32
    // FIXME: Autoload all these functions so users don't need to
    // link in imagehlp.dll.
    if (! SymInitialize (GetCurrentProcess (), NULL, TRUE))
    {
    MYWRITELIT (fd, ("failed to dump stack trace:"
             " cannot get symbolic information\n"));
    return;
    }
 
    union SYMBUFFER {
    IMAGEHLP_SYMBOL sym;
    BYTE        buffer [ sizeof (IMAGEHLP_SYMBOL) + 512 ];
    };
 
    unsigned        level = 0;
    CONTEXT     context;
    STACKFRAME      frame;
    SYMBUFFER       symbol;
    IMAGEHLP_MODULE module;
    char        modulename [MAX_PATH];
    DWORD       section;
    DWORD       offset;
    const int       buf_size = 2*40+6;   // ample for two 128+ bit numbers
    char        buf [buf_size];
    // DWORD        exceptargs [] = { (DWORD) &context };
 
    // FIXME: XP 64-bit adds: RtlCaptureContext (&context);
    // This is documented to *not* work, but apparently it does.
    context.ContextFlags = CONTEXT_FULL;
    if (! GetThreadContext (GetCurrentThread (), &context))
    return;
 
    // LPTOP_LEVEL_EXCEPTION_FILTER oldseh
    //  = SetUnhandledExceptionFilter (&GrabExceptionContext);
    // RaiseException (0, 0, 1, exceptargs);
    // SetUnhandledExceptionFilter (oldseh);
 
    memset (&module, 0, sizeof (module));
    memset (&frame, 0, sizeof (frame));
 
    module.SizeOfStruct     = sizeof (module);
 
    frame.AddrPC.Offset     = context.Eip;
    frame.AddrPC.Mode       = AddrModeFlat;
    frame.AddrStack.Offset  = context.Esp;
    frame.AddrStack.Mode    = AddrModeFlat;
    frame.AddrFrame.Offset  = context.Ebp;
    frame.AddrFrame.Mode    = AddrModeFlat;
 
    while (true)
    {
    if (! StackWalk (IMAGE_FILE_MACHINE_I386,
             GetCurrentProcess (),
             GetCurrentThread (),
             &frame,
             &context,
             NULL,
             SymFunctionTableAccess,
             SymGetModuleBase,
             NULL)
        || frame.AddrFrame.Offset == 0)
        break;
 
    // FIXME: Throw away everything above stacktrace?  Keep looping
    // below until the name includes something we understand?
 
    // Print stack frame too?  If we know how many arguments there
    // are (from demangling function name -- see below, could count
    // commas), args are: *((ULONG *)frame.AddrFrame.Offset+2+ARG).
    MYWRITE (fd, buf, snprintf (buf, buf_size, "(%2u) 0x%08lx 0x%08lx   ",
                    level, frame.AddrPC.Offset,
                    frame.AddrFrame.Offset));
 
    memset (&symbol, 0, sizeof (symbol));
    symbol.sym.SizeOfStruct = sizeof (symbol);
    symbol.sym.MaxNameLength = sizeof (symbol) - sizeof (symbol.sym);
 
    offset = 0;
    if (SymGetSymFromAddr (GetCurrentProcess (), frame.AddrPC.Offset,
                   &offset, &symbol.sym))
    {
        // FIXME: Demangle name with:
        //   UnDecorateSymbolName (name, undecname, sizeof (undecname),
        //              UNDNAME_COMPLETE
        //              | UNDNAME_NO_THISTYPE
        //              | UNDNAME_NO_SPECIAL_SYMS
        //              | UNDNAME_NO_MEMBER_TYPE
        //              | UNDNAME_NO_MS_KEYWORDS
        //              | UNDNAME_NO_ACCESS_SPECIFIERS);
        MYWRITE (fd, symbol.sym.Name, STDC::strlen (symbol.sym.Name));
        MYWRITE (fd, buf, snprintf (buf, buf_size, " + %lx", offset));
 
        if (SymGetModuleInfo (GetCurrentProcess(), frame.AddrPC.Offset,
                  &module))
        {
        MYWRITELIT (fd, " [");
        MYWRITE (fd, module.ImageName,
             STDC::strlen (module.ImageName));
        MYWRITELIT (fd, "]");
        }
    }
    else
    {
        GetLogicalAddress ((PVOID) frame.AddrPC.Offset,
                   modulename, sizeof (modulename),
                   section, offset);
        MYWRITE (fd, buf, snprintf (buf, buf_size, "%04lx:%08lx [", section, offset));
        MYWRITE (fd, modulename, STDC::strlen (modulename));
        MYWRITELIT (fd, "]");
    }
    MYWRITELIT (fd, "\n");
    ++level;
    }
    SymCleanup (GetCurrentProcess ());
 
#elif (HAVE_U_STACK_TRACE || HAVE_XL_TRBK)      // hp-ux, aix
    // FIXME: deal with inability to duplicate the file handle
    int stderrfd = dup (STDERR_FILENO);
    if (stderrfd == -1)
    return;
 
    int newfd    = dup2 (fd, STDERR_FILENO);
    if (newfd == -1)
    {
    close (stderrfd);
    return;
    }
 
# if HAVE_U_STACK_TRACE     // hp-ux
    U_STACK_TRACE ();
# elif HAVE_XL_TRBK     // aix
    xl__trbk ();
# else
#  error "oops, you shouldn't have gotten here!"
# endif
 
    fflush (stderr);
    dup2 (stderrfd, STDERR_FILENO);
    close (newfd);
#elif HAVE_LINUX_UNWIND_BACKTRACE
    CxxUtils::backtraceByUnwind (stacktraceLine, fd);
 
#elif HAVE_BACKTRACE_SYMBOLS_FD && HAVE_DLADDR      // linux
    // we could have used backtrace_symbols_fd, except its output
    // format is pretty bad, so recode that here :-(
    void        *trace [MAX_BACKTRACE_DEPTH];
    int         depth = backtrace (trace, MAX_BACKTRACE_DEPTH);
 
    for (int n = 0; n < depth; ++n/*, nbufs = 0*/)
    {
    unsigned long   addr = (unsigned long) trace [n];
        stacktraceLine (fd, addr);
    }
 
#elif HAVE_EXCPT_H && HAVE_PDSC_H && HAVE_RLD_INTERFACE_H // tru64
    // Tru64 stack walk.  Uses the exception handling library and the
    // run-time linker's core functions (loader(5)).  FIXME: Tru64
    // should have _RLD_DLADDR like IRIX below.  Verify and update.
 
    const int   buffer_size = 100 + BitTraits<unsigned long>::HexDigits * 2 + 11;
    char    buffer [buffer_size];
    sigcontext  context;
    int     rc = 0;
 
    exc_capture_context (&context);
    while (!rc && context.sc_pc)
    {
    // FIXME: Elf32?
    pdsc_crd *func, *base, *crd
      = exc_remote_lookup_function_entry(0, 0, context.sc_pc, 0, &func, &base);
    Elf32_Addr addr = PDSC_CRD_BEGIN_ADDRESS(base, func);
    // const char *name = _rld_address_to_name(addr);
    const char *name = "<unknown function>";
    snprintf (buffer, buffer_size, " 0x%012lx %.100s + 0x%lx\n",
          context.sc_pc, name, context.sc_pc - addr);
    write (fd, buffer, STDC::strlen(buffer));
    rc = exc_virtual_unwind(0, &context);
    }
 
#elif HAVE_EXCEPTION_H && defined __sgi         // irix
    // IRIX stack walk -- like Tru64 but with a little different names.
    // NB: The guard above is to protect against unrelated <exception.h>
    //   provided by some compilers (e.g. KCC 4.0f).
    // NB: libexc.h has trace_back_stack and trace_back_stack_and_print
    //   but their output isn't pretty and nowhere as complete as ours.
    char       buffer [340];
    sigcontext context;
 
    exc_setjmp (&context);
    while (context.sc_pc >= 4)
    {
    // Do two lookups, one using exception handling tables and
    // another using _RLD_DLADDR, and use the one with a smaller
    // offset.  For signal handlers we seem to get things wrong:
    // _sigtramp's exception range is huge while based on Dl_info
    // the offset is small -- but both supposedly describe the
    // same thing.  Go figure.
    char            *name = 0;
    const char      *libname = 0;
    const char      *symname = 0;
    Elf32_Addr      offset = ~0L;
 
    // Do the exception/dwarf lookup
    Elf32_Addr      pc = context.sc_pc;
    Dwarf_Fde       fde = find_fde_name (&pc, &name);
    Dwarf_Addr      low_pc = context.sc_pc;
    Dwarf_Unsigned  udummy;
    Dwarf_Signed    sdummy;
    Dwarf_Ptr       pdummy;
    Dwarf_Off       odummy;
    Dwarf_Error     err;
 
    symname = name;
 
    // Determine offset using exception descriptor range information.
    if (dwarf_get_fde_range (fde, &low_pc, &udummy, &pdummy, &udummy,
                 &odummy, &sdummy, &odummy, &err) == DW_DLV_OK)
        offset = context.sc_pc - low_pc;
 
       // Now do a dladdr() lookup.  If the found symbol has the same
       // address, trust the more accurate offset from dladdr();
       // ignore the looked up mangled symbol name and prefer the
       // demangled name produced by find_fde_name().  If we find a
       // smaller offset, trust the dynamic symbol as well.  Always
       // trust the library name even if we can't match it with an
       // exact symbol.
    Elf32_Addr      addr = context.sc_pc;
    Dl_info         info;
 
    if (_rld_new_interface (_RLD_DLADDR, addr, &info))
    {
        if (info.dli_fname && info.dli_fname [0])
        libname = info.dli_fname;
 
        Elf32_Addr symaddr = (Elf32_Addr) info.dli_saddr;
        if (symaddr == low_pc)
        offset = addr - symaddr;
        else if (info.dli_sname
             && info.dli_sname [0]
             && addr - symaddr < offset)
        {
        offset = addr - symaddr;
        symname = info.dli_sname;
        }
    }
 
    // Print out the result
    if (libname && symname)
            write (fd, buffer, snprintf
           (buffer, buffer_size, " 0x%012lx %.100s + 0x%lx [%.200s]\n",
            addr, symname, offset, libname));
    else if (symname)
        write (fd, buffer, snprintf
           (buffer, buffer_size, " 0x%012lx %.100s + 0x%lx\n",
            addr, symname, offset));
    else
        write (fd, buffer, snprintf
           (buffer, buffer_size, " 0x%012lx <unknown function>\n", addr));
 
    // Free name from find_fde_name().
    free (name);
 
    // Check for termination.  exc_unwind() sets context.sc_pc to
    // 0 or an error (< 4).  However it seems we can't unwind
    // through signal stack frames though this is not mentioned in
    // the docs; it seems that for those we need to check for
    // changed pc after find_fde_name().  That seems to indicate
    // end of the post-signal stack frame.  (FIXME: Figure out how
    // to unwind through signal stack frame, e.g. perhaps using
    // sigcontext_t's old pc?  Or perhaps we can keep on going
    // down without doing the symbol lookup?)
    if (pc != context.sc_pc)
        break;
 
    exc_unwind (&context, fde);
    }
 
#elif defined PROG_PSTACK               // solaris
# ifdef PROG_CXXFILT
#  define CXXFILTER " | " PROG_CXXFILT
# else
#  define CXXFILTER
# endif
    // 64 should more than plenty for a space and a pid.
    const int buffer_size = sizeof(PROG_PSTACK) + 1 + BitTraits<unsigned long>::Digits
                 + 3 + sizeof(PROG_CXXFILT) + BitTraits<int>::Digits + 1;
    char buffer [buffer_size];
    snprintf (buffer, buffer_size, "%s %lu%s 1>&%d", PROG_PSTACK, (unsigned long) getpid (),
         "" CXXFILTER, fd);
    system (buffer);
# undef CXXFILTER
 
#elif __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
    // FIXME: Check for _Unwind*, compilers other than GCC support this API
    _Unwind_Backtrace (unwindWalkStack, &fd);
#endif
 
    // FIXME: mpatrol has some generic unix unwind code.
    // FIXME: from unix faq: ask debugger to dump stack trace
    // with something like:
    //   - gdb: echo "thread apply all where\nwhere\ndetach" | gdb $prog $pid
    //   - dbx: echo "where\ndetach" | dbx -a $program_path $pid
    //   - dbx (aix): echo "where\ndetach" | dbx -p $program_path $pid
}

void
DebugAids::coredump (int sig, ...)
{
#ifndef _WIN32
    // FIXME: Forking vs. threads -- need to sort out what is safe.
    // FIXME: Provide a resource limits interface so that core
    // resource limits can be raised?
 
    pid_t  corepid;
    int     status;
 
    ::unlink ("core");
    if ((corepid = ::fork ()) == 0)
    {
    // In child: re-raise the signal, thus killing the process and
    // producing a core dump.  Make sure 1) the signal is not
    // blocked so that we won't return to the caller, 2) we have a
    // signal that is fatal, 3) the signal falls to its default
    // handler to produce the dump.
 
#ifdef SIGUSR1
    // SIGUSR1 does not cause a core dump; use abort() instead
    if (sig == SIGUSR1)
        sig = SIGABRT;  // Could be SIGIOT if SIGABRT is not defined
#endif
    Signal::handle (sig, (Signal::HandlerType) (void*)SIG_DFL);
    Signal::block (sig, false);
    Signal::raise (sig);
 
    // Yikes, this shouldn't happen.  ASSERT isn't right here.  If
    // raise() failed to deliver the signal, abort() is unlikely
    // to work any better, but try it anyway.  Then make sure we
    // die so that we won't return to the caller from the child.
    abort ();
        // cppcheck-suppress unreachableCode
    _exit (255);
    }
    else if (corepid > 0) {
      pid_t wait_pid;
      do {
    wait_pid = ::waitpid (corepid, &status, 0);
      } while (wait_pid == -1 && errno == EINTR);
    }
#endif // !_WIN32
}
 

unsigned long
DebugAids::enableCoreFiles()
{
  struct rlimit core_limit;
  getrlimit(RLIMIT_CORE, &core_limit);
 
  unsigned long old_limit = core_limit.rlim_cur;
  core_limit.rlim_cur = core_limit.rlim_max;
  if ( setrlimit(RLIMIT_CORE, &core_limit) == 0 ) {
    return core_limit.rlim_cur;
  }
  else {
    return old_limit;
  }
}

void DebugAids::disableCoreFiles()
{
  struct rlimit core_limit;
  core_limit.rlim_cur = 0;
  core_limit.rlim_max = 0;
  setrlimit(RLIMIT_CORE, &core_limit);
}
 
 
} // namespace Athena                             wlav