[Valgrind-users] using valgrind to detect array overruns

[R O <mu...@ya...>]

Hello,

I am trying to find a subtle bug that overwrites memory but which is
not detectable with valgrind. I am using ROOT based code
(http/root.cern.ch/) and when I ran under valgrind with
--tool=mememcheck, valgrind can not detect the error that causes memory
corruption. Part of the problem could be that root has its own
interpreter.

My question is:

is it possible to detect with valgrind memory overwrites where a
program writes to a memory space pass allocated space of a particular
array but while still writing to the memory that was allocated
somewhere else in the program?

For example, valgrind can not detect the memory overwrite in the
example below, which is likely to be what is happening in my case.

Thank you very much,
Rust

//------- overflow.cc -----------------------------------
// g++ -o overflow overflow.cc
//
#include <iostream>
using namespace std;
int main (int argc, char *argv[])
{
   int array1[10] = {0};  // initialize to 0
   int array2[10] = {0};  // initialize to 0
   int array3[10] = {0};  // initialize to 0

   // Bad!: Fill the 10 element array with 20 elements
   for (int ind=0; ind<20; ++ind) {
       array2[ind] = ind;
   }

   // Print out the arrays
   for (int ind=0; ind<10; ++ind) {
       cout << "array1["<<ind<<"] = " << array1[ind] << endl;
   }
   for (int ind=0; ind<10; ++ind) {
       cout << "array2["<<ind<<"] = " << array2[ind] << endl;
   }
   for (int ind=0; ind<10; ++ind) {
       cout << "array3["<<ind<<"] = " << array3[ind] << endl;
   }
   return 0;
} // end of main()
//-------------------------------------------------------



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