istream

[Frederic Tran_Minh <ftran at sophia dot inria dot fr>]

 hi,

 this is perhaps not a bug, but at least a different behavior between
 gcc 2.95 and gcc 3.0, and you perhaps can give me a hint for porting.


 the sample attached program makes 2 tests reading n bytes from
 a file ;
    test1 : file == std::cin     fails on gcc3,  succeeds on gcc2.95
    test2 : file is a std::ifstream, succeeds on both.

 Unfortunately I cannot attach you the input file since it's a 5769604
bytes confidential file, but **the same file** is used as input in **all**
cases.

 you will find as attached files

  1/ the bug diagnostic          bugrep00
  2/ the sample source file      test_istream.cc


 Fred
To: gcc-bugs@gcc.gnu.org

Subject: istream


 hi,

 this is perhaps not a bug, but at least a different behavior between
 gcc 2.95 and gcc 3.0, and you perhaps can give me a hint for porting.


 the sample attached program makes 2 tests reading n bytes from
 a file ;
    test1 : file == std::cin     fails on gcc3,  succeeds on gcc2.95
    test2 : file is a std::ifstream, succeeds on both.

 Unfortunately I cannot attach you the input file since it's a 5769604 bytes
 confidential file, but **the same file** is used as input in **all** cases.


Platform 1
----------

> uname -a
SunOS gollum 5.6 Generic_105181-26 sun4u sparc SUNW,Ultra-5_10



> g++ -v
Reading specs from /usr/local/gcc/lib/gcc-lib/sparc-sun-solaris2.6/2.95.3/specs
gcc version 2.95.3 20010315 (release)


Configuration/Compilation of gcc/g++ : unknown



Compilation command line :
> g++ -o test_istream test_istream.cc


Input file :
> ls -l $IMDIR/NewRef/orlycut_ref1m_03_60_sr.cv.ima
-rw-r--r--   1 ftran    ariana   5769604 May 22 15:35 ../Images/Images_Astrium/NewRef/orlycut_ref1m_03_60_sr.cv.ima


TEST1 (#define TEST1  #undef TEST2)

Command line :
> test_istream 5750388 < $IMDIR/NewRef/orlycut_ref1m_03_60_sr.cv.ima

Output :
Reading 5750388 chars ...
 Streampos = 0
 Read 5750388 chars
 Streampos = 5750388


Diagnostic : OK


TEST2 (#undef TEST1 #define TEST2)

Command line :
> test_istream 5750388 $IMDIR/NewRef/orlycut_ref1m_03_60_sr.cv.ima

Output
Reading 5750388 chars ...
 Streampos = 0
 Read 5750388 chars
 Streampos = 5750388


Diagnostic: OK




Platform 2
----------

> uname -a
SunOS fermi 5.6 Generic_105181-25 sun4u sparc SUNW,Ultra-80



> g++ -v
Reading specs from /lpps04/simage/ARIANA/Soft/gnu/lib/gcc-lib/sparc-sun-solaris2.6/3.0.1/specs
Configured with: /lpps04/simage/ARIANA/Soft/gnu/packages/gcc-3.0.1/configure --prefix=/lpps04/simage/ARIANA/Soft/gnu
Thread model: posix
gcc version 3.0.1


Configuration/Compilation of gcc/g++ : 
  srcdir/configure --prefix=/lpps04/simage/ARIANA/Soft/gnu
  make bootstrap

 (no modification of gcc/g++ source)


Compilation command line :
> g++ -o test_istream test_istream.cc


Input file :
> ls -l $IMDIR/NewRef/orlycut_ref1m_03_60_sr.cv.ima
-rw-r--r--   1 ftran    ariana   5769604 May 22 15:35 ../Images/Images_Astrium/NewRef/orlycut_ref1m_03_60_sr.cv.ima


TEST1 (#define TEST1  #undef TEST2)

Command line :
> test_istream 5750388 < $IMDIR/NewRef/orlycut_ref1m_03_60_sr.cv.ima

Output :
Reading 5750388 chars ...
 Streampos = 0
 Read 5748727 chars
 Streampos = -1


Diagnostic : fails before real end of file


TEST2 (#undef TEST1 #define TEST2)

Command line :
> test_istream 5750388 $IMDIR/NewRef/orlycut_ref1m_03_60_sr.cv.ima

Output
Reading 5750388 chars ...
 Streampos = 0
 Read 5750388 chars
 Streampos = 5750388


Diagnostic: OK
#include <iostream>
#include <cassert>
#include <cstdlib>

//#undef TEST1
#define TEST2

#ifdef TEST1

main(int argc, char **argv) {

  assert(argc>1);

  unsigned int n = atoi(argv[1]);
  char *X = new char[n];

  std::cerr << "Reading " << n<< " chars ..." << std::endl;
  std::cerr << " Streampos = " << std::cin.tellg() << std::endl;
  std::cin.read(X,n);
  std::cerr << " Read " << std::cin.gcount() << " chars"  << std::endl;
  std::cerr << " Streampos = " << std::cin.tellg() << std::endl;

  delete [] X;

  return 0;
}

#endif

#ifdef TEST2

#include <fstream>

main(int argc, char **argv) {

  assert(argc>2);

  unsigned int n = atoi(argv[1]);
  char *X = new char[n];

  std::ifstream stream(argv[2]);

  std::cerr << "Reading " << n<< " chars ..." << std::endl;
  std::cerr << " Streampos = " << stream.tellg() << std::endl;
  stream.read(X,n);
  std::cerr << " Read " << stream.gcount() << " chars"  << std::endl;
  std::cerr << " Streampos = " << stream.tellg() << std::endl;

  stream.close();
  delete [] X;

  return 0;
}
#endif