IJ08152: BAD CAST CAUSING INCORRECT AIX _LARGE_FILES TELLG() VALUE

XL C for AIX, V13.1.3.5 Fix Pack (July 2018)
XL C/C++ for AIX, V13.1.3.5 Fix Pack (July 2018)
XL C for AIX, V13.1.3.6 Fix Pack (May 2019)
XL C/C++ for AIX, V13.1.3.6 Fix Pack (May 2019)

APAR status

• Closed as program error.

Error description

• When compiling with large file support, a bad cast within the
  C++ runtime is causing bad values from the fstream tellg()
  function.
  
  With large file support, 'long long' types are the main datatype
  for managing the large size of the file.  When tellg() is called
  it relies on a macro called _FPOSOFF in <yvals.h> that does a
  cast to long, instead of long long.  This bad cast cascades back
  to the 'pos_type'/''streampos' returned by tellg(), which gives
  an incorrect value.
  
  
  
     === TEST CASE ===
  
  #include<iostream>
  #include<fstream>
  
  std::fstream fs("file", std::ios_base::in);
   // Where 'file' is a large file
  
  int main()
  {
   using namespace std;
  
   fs.seekg(0, std::ios_base::end);
   cout << "tellg() =            " << fs.tellg() << endl;
   cout << "(uint32_t)tellg() =  " << (uint32_t)fs.tellg() <<endl;
  };
  
  
  OUPUT:
  $ xlC -qlonglong -D_LARGE_FILES apar.cpp
  $ ./a.out
  tellg() =            -562486541
  (uint32_t)tellg() =  3732480755
  $
  
  EXPECTED OUTPUT:
  $ xlC -qlonglong -D_LARGE_FILES apar.cpp
  $ ./a.out
  tellg() =            3732480755
  (uint32_t)tellg() =  3732480755
  $
  

Local fix

• Cast return value of tellg() to uint32_t
  

Problem summary

• PROBLEM DESCRIPTION:
  When compiling with large file support on AIX, a bad cast
  within the C++ runtime is causing bad values from the fstream
  tellg() function.
  
  USERS AFFECTED:
  User who use the file-based stream library (fstream) with large
  file support.
  

Problem conclusion

• Please apply the fix if you are using large file support along
  with the file-based stream library.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

  IV95280

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  XL C FOR AIX

• Fixed component ID

  5725C7100

Applicable component levels

• RD13 PSN IV95280

     UP06/09/13