Re: [OMPI users] Sending string causes memory errors

Gilles Gouaillardet Thu, 3 Mar 2016 00:53:25 -0500 (EST)

I was unable to reproduce this in my environment.

here is a slightly modified version of your test program.

buffers are 64 bytes aligned and the string (including the nullterminator) is 64 bytes long,

hopefully, strlen will not complain any more.


Cheers,

Gilles

On 3/3/2016 12:51 AM, Florian Lindner wrote:

Hello Gilles,

Am Mittwoch, 2. März 2016, 23:36:56 CET schrieb Gilles Gouaillardet:

Florian,

under the hood, strlen() can use vector instructions, and then read memory
above the end of the string. valgrind is extremely picky and does warn
about that.
iirc, there are some filter options not to issue these warnings, but I
forgot the details.

Ok, i'll try to research in that direction.

can you try to send "Bonjour" instead of "Halo" and see if the warning
disappear ?

They are still there. But, was this meant as a joke or didn't I understand?

Best,
Florian

Cheers,

Gilles

PS if it works, do not jump to the erroneous conclusion valgrind likes
French and dislikes German ;-)

On Wednesday, March 2, 2016, Florian Lindner <mailingli...@xgm.de> wrote:

Hello,

using OpenMPI 1.10.2 and valgrind 3.11.0 I try to use the code below to
send a c++ string.

It works fine, but running through valgrind gives a lot of memory errors,
invalid read of size...

What is going wrong there?

Valgrind output, see below.

Thanks!
Florian


// Compile with: mpicxx -std=c++11 -g -O0 -Wall -Wextra mpi.cpp
#include <mpi.h>
#include <iostream>
#include <string>

using namespace std;


void receive() {
   int length = 0;
   MPI_Status status;
   MPI_Probe(MPI_ANY_SOURCE, 0, MPI_COMM_WORLD, &status);
   MPI_Get_count(&status, MPI_CHAR, &length);
   cout << "Stringlength = " << length << endl;
   char cstr[length];
   MPI_Recv(cstr,
            length,
            MPI_CHAR,
            MPI_ANY_SOURCE,
            MPI_ANY_TAG,
            MPI_COMM_WORLD,
            MPI_STATUS_IGNORE);
   cout << cstr << endl;
}

void send(int rankReceiver) {
   std::string s = "Hallo";
   MPI_Send(s.c_str(),
            s.size()+1,
            MPI_CHAR,
            rankReceiver,
            0,
            MPI_COMM_WORLD);
}

int main(int argc, char* argv[])
{
   int rank;
   MPI_Init(&argc, &argv);

   MPI_Comm_rank(MPI_COMM_WORLD, &rank);
   if (rank == 0)
     send(1);
   else {
     receive();
   }
   MPI_Finalize();
   return 0;
}


VALGRIND OUTPUT

% mpicxx -std=c++11 -g -O0 -Wall -Wextra mpi.cpp && mpirun -n 2 ./a.out
Stringlength = 6
Hallo
florian@asaru ~/scratch (git)-[master] %
LD_PRELOAD=/usr/lib/valgrind/libmpiwrap-amd64-linux.so mpirun -n 2 valgrind
./a.out
==9290== Memcheck, a memory error detector
==9290== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==9290== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==9290== Command: ./a.out
==9290==
==9291== Memcheck, a memory error detector
==9291== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==9291== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==9291== Command: ./a.out
==9291==
valgrind MPI wrappers  9290: Active for pid 9290
valgrind MPI wrappers  9291: Active for pid 9291
valgrind MPI wrappers  9290: Try MPIWRAP_DEBUG=help for possible options
valgrind MPI wrappers  9291: Try MPIWRAP_DEBUG=help for possible options
Stringlength = 6
==9291== Invalid read of size 1
==9291==    at 0x4C2DBA2: strlen (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==9291==    by 0x56852D8: length (char_traits.h:267)
==9291==    by 0x56852D8: std::basic_ostream<char, std::char_traits<char>

& std::operator<< <std::char_traits<char> >(std::basic_ostream<char,

std::char_traits<char> >&, char const*) (ostream:562)
==9291==    by 0x408A39: receive() (mpi.cpp:22)
==9291==    by 0x408B61: main (mpi.cpp:46)
==9291==  Address 0xffefff870 is on thread 1's stack
==9291==  in frame #2, created by receive() (mpi.cpp:8)
==9291==
==9291== Invalid read of size 1
==9291==    at 0x4C2DBB4: strlen (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==9291==    by 0x56852D8: length (char_traits.h:267)
==9291==    by 0x56852D8: std::basic_ostream<char, std::char_traits<char>

& std::operator<< <std::char_traits<char> >(std::basic_ostream<char,

std::char_traits<char> >&, char const*) (ostream:562)
==9291==    by 0x408A39: receive() (mpi.cpp:22)
==9291==    by 0x408B61: main (mpi.cpp:46)
==9291==  Address 0xffefff871 is on thread 1's stack
==9291==  in frame #2, created by receive() (mpi.cpp:8)
==9291==
==9291== Invalid read of size 1
==9291==    at 0x60A0FF1: _IO_file_xsputn@@GLIBC_2.2.5 (in /usr/lib/
libc-2.23.so)
==9291==    by 0x6096D1A: fwrite (in /usr/lib/libc-2.23.so)
==9291==    by 0x5684F75: sputn (streambuf:451)
==9291==    by 0x5684F75: __ostream_write<char, std::char_traits<char> >
(ostream_insert.h:50)
==9291==    by 0x5684F75: std::basic_ostream<char, std::char_traits<char>

& std::__ostream_insert<char, std::char_traits<char>
(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)

(ostream_insert.h:101)
==9291==    by 0x56852E6: std::basic_ostream<char, std::char_traits<char>

& std::operator<< <std::char_traits<char> >(std::basic_ostream<char,

std::char_traits<char> >&, char const*) (ostream:561)
==9291==    by 0x408A39: receive() (mpi.cpp:22)
==9291==    by 0x408B61: main (mpi.cpp:46)
==9291==  Address 0xffefff874 is on thread 1's stack
==9291==  in frame #4, created by receive() (mpi.cpp:8)
==9291==
==9291== Invalid read of size 1
==9291==    at 0x60A100D: _IO_file_xsputn@@GLIBC_2.2.5 (in /usr/lib/
libc-2.23.so)
==9291==    by 0x6096D1A: fwrite (in /usr/lib/libc-2.23.so)
==9291==    by 0x5684F75: sputn (streambuf:451)
==9291==    by 0x5684F75: __ostream_write<char, std::char_traits<char> >
(ostream_insert.h:50)
==9291==    by 0x5684F75: std::basic_ostream<char, std::char_traits<char>

& std::__ostream_insert<char, std::char_traits<char>
(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)

(ostream_insert.h:101)
==9291==    by 0x56852E6: std::basic_ostream<char, std::char_traits<char>

& std::operator<< <std::char_traits<char> >(std::basic_ostream<char,

std::char_traits<char> >&, char const*) (ostream:561)
==9291==    by 0x408A39: receive() (mpi.cpp:22)
==9291==    by 0x408B61: main (mpi.cpp:46)
==9291==  Address 0xffefff873 is on thread 1's stack
==9291==  in frame #4, created by receive() (mpi.cpp:8)
==9291==
==9291== Invalid read of size 2
==9291==    at 0x4C2F9C0: __GI_memcpy (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==9291==    by 0x60A0F3A: _IO_file_xsputn@@GLIBC_2.2.5 (in /usr/lib/
libc-2.23.so)
==9291==    by 0x6096D1A: fwrite (in /usr/lib/libc-2.23.so)
==9291==    by 0x5684F75: sputn (streambuf:451)
==9291==    by 0x5684F75: __ostream_write<char, std::char_traits<char> >
(ostream_insert.h:50)
==9291==    by 0x5684F75: std::basic_ostream<char, std::char_traits<char>

& std::__ostream_insert<char, std::char_traits<char>
(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)

(ostream_insert.h:101)
==9291==    by 0x56852E6: std::basic_ostream<char, std::char_traits<char>

& std::operator<< <std::char_traits<char> >(std::basic_ostream<char,

std::char_traits<char> >&, char const*) (ostream:561)
==9291==    by 0x408A39: receive() (mpi.cpp:22)
==9291==    by 0x408B61: main (mpi.cpp:46)
==9291==  Address 0xffefff870 is on thread 1's stack
==9291==  in frame #5, created by receive() (mpi.cpp:8)
==9291==
==9291== Invalid read of size 1
==9291==    at 0x4C2F9F8: __GI_memcpy (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==9291==    by 0x60A0F3A: _IO_file_xsputn@@GLIBC_2.2.5 (in /usr/lib/
libc-2.23.so)
==9291==    by 0x6096D1A: fwrite (in /usr/lib/libc-2.23.so)
==9291==    by 0x5684F75: sputn (streambuf:451)
==9291==    by 0x5684F75: __ostream_write<char, std::char_traits<char> >
(ostream_insert.h:50)
==9291==    by 0x5684F75: std::basic_ostream<char, std::char_traits<char>

& std::__ostream_insert<char, std::char_traits<char>
(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)

(ostream_insert.h:101)
==9291==    by 0x56852E6: std::basic_ostream<char, std::char_traits<char>

& std::operator<< <std::char_traits<char> >(std::basic_ostream<char,

std::char_traits<char> >&, char const*) (ostream:561)
==9291==    by 0x408A39: receive() (mpi.cpp:22)
==9291==    by 0x408B61: main (mpi.cpp:46)
==9291==  Address 0xffefff874 is on thread 1's stack
==9291==  in frame #5, created by receive() (mpi.cpp:8)
==9291==
Hallo
==9291==
==9291== HEAP SUMMARY:
==9291==     in use at exit: 96,351 bytes in 247 blocks
==9291==   total heap usage: 15,020 allocs, 14,773 frees, 13,362,383 bytes
allocated
==9291==
==9291== LEAK SUMMARY:
==9291==    definitely lost: 9,154 bytes in 39 blocks
==9291==    indirectly lost: 4,008 bytes in 22 blocks
==9291==      possibly lost: 0 bytes in 0 blocks
==9291==    still reachable: 83,189 bytes in 186 blocks
==9291==         suppressed: 0 bytes in 0 blocks
==9291== Rerun with --leak-check=full to see details of leaked memory
==9291==
==9291== For counts of detected and suppressed errors, rerun with: -v
==9291== ERROR SUMMARY: 14 errors from 6 contexts (suppressed: 0 from 0)
==9290==
==9290== HEAP SUMMARY:
==9290==     in use at exit: 96,351 bytes in 247 blocks
==9290==   total heap usage: 15,018 allocs, 14,771 frees, 13,370,045 bytes
allocated
==9290==
==9290== LEAK SUMMARY:
==9290==    definitely lost: 9,154 bytes in 39 blocks
==9290==    indirectly lost: 4,008 bytes in 22 blocks
==9290==      possibly lost: 0 bytes in 0 blocks
==9290==    still reachable: 83,189 bytes in 186 blocks
==9290==         suppressed: 0 bytes in 0 blocks
==9290== Rerun with --leak-check=full to see details of leaked memory
==9290==
==9290== For counts of detected and suppressed errors, rerun with: -v
==9290== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

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#include <mpi.h>
#include <iostream>
#include <string>

using namespace std;


void receive() {
  int length = 0;
  MPI_Status status;
  MPI_Probe(MPI_ANY_SOURCE, 0, MPI_COMM_WORLD, &status);
  MPI_Get_count(&status, MPI_CHAR, &length);
  cout << "Stringlength = " << length << endl;
  __attribute__((aligned(64))) char cstr[length];
  MPI_Recv(cstr,
           length,
           MPI_CHAR,
           MPI_ANY_SOURCE,
           MPI_ANY_TAG,
           MPI_COMM_WORLD,
           MPI_STATUS_IGNORE);
  cout << cstr << endl;
}

void send(int rankReceiver) {
  __attribute__((aligned(64))) std::string s = 
"123456789012345678901234567890123456789012345678901234567890123";
  MPI_Send(s.c_str(),
           s.size()+1,
           MPI_CHAR,
           rankReceiver,
           0,
           MPI_COMM_WORLD);
}

int main(int argc, char* argv[])
{
  int rank;
  MPI_Init(&argc, &argv);

  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  if (rank == 0)
    send(1);
  else {
    receive();
  }
  MPI_Finalize();
  return 0;
}

Re: [OMPI users] Sending string causes memory errors

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