C++ :: Filling Memory Causes Application Crash
Jul 5, 2012
I have a question about allocating 2MB memory then filling it...
@ Platform:
=> DOS, and application is compiled/linked via Watcom C + DOS32/A (...memory model is "flat" mode)
@ phenomenon:
1. I allocate 2M memory by calloc() function. Then I got "!NULL" and it means allocating 2MB memory is ok( right ? )
2. then I tried to "fill" this 2MB memory by for loop(one byte by one byte) like below:
for( DWORD i=0; i<0x200000; i++) {
*((BYTE *)(A[0].B[0]->C) + i ) = 0x5A; // C is 4-byte address value
}
here :
* DWORD means "unsigned long(4-byte)" and 0x200000 means "2MByte"
* in actual case the value of pointer(to allocated memory) is 3019AF3C(~768MB) <- running in flat mode...
3. after filling this range of memory(2MB) the application crashed...
@ my observations:
1. if allocating 2MB and no fill(no write data to memory) => OK
2. if allocating 2MB and just fill the former 32 bytes => OK
3. if allocating 4KB and fill all => OK
my question is: why can't I filling this 2M memory totally "even memory allocation succeeds" ?
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Mar 9, 2013
I'm using C++ Form Application in Visual Studio 2010. I defined a new two dimentional array. like this "static int dizi[26][26];" I want to change the value when I clicked the button1. For example, I can change as dizi[2][3]=1. But I couldn't change like in this code. dizi[a][b]=1 didn't happen.
Error is... "access violation exception was unhandled. attempted to read or write protected memory. this is often an indication that other memory is corrupt."
for(int i=1;i<=26;i++){
uzunluk=0;
for(int uzun=1;uzun<=26;uzun++){
if(ogrenci[i].ders[uzun]!=0)
uzunluk+=1;
else break;
[Code] ....
I don't use zeroth variable here.So, It started from 1. My problem is variable can't be changed.I can't assign a value to variable. I have to use 'ogrenci[i].ders[j]'s index for dizi array in this code. It's really weird.
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Aug 18, 2014
I have a question concerning shared memory (in linux-environment). In our company we currently have an application that is restarted once in a while. There are multiple instances running of this application (on different physical machines), and all access the same centralized database. Because of IO and Network bottleneck the start gets very slow, and takes about 10 Minutes. Besides some new data, most of the data stays the same, so reading from the database again is quite redundant. An idea is to write all relevant object to a shared memory segment, when the application is shut down. A second dummy process attaches to the same shared memory (just so that some process is still attached). If the application is restarted, it is attached again to its shared memory, and reads it to its own adress range again. There might occur a difference regarding the data so it might me necessary to load some new data afterwards, but that is different problem.
The current idea is to serialize all Objects (could be about 1-2 Gigabyte) with Apache Thrift, and write them into shared memory. With Thrift the data is more or less ordered, so creating the objects anew is possibly easier (not sure here).
My Question is:
- Does it even make sense to consider shared memory in this scenario. I've read a lot stuff about in the last few days, and for now I don't see big disadvantages (except if the application crashes, in this case I've to read from database again). On the other hand I don't know how to really implement this functionality (as I'm no experienced Developer)
- Should I aim for Boost::Interproces, considering even memory mappable files, or stay with the traditional shmat (and stuff..)?
- I guess 1-2 Gigabyte shared memory will be necessary. This amount is only needed in the gap between application shutdown and restart. Will the sheer amount of needed shared memory be a problem (all examples I found just used a few Bytes or Kilobytes)
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Dec 15, 2012
The application that I ported from 32 bit linux to 64 bit linux is crashing due to unknown memory corruption Also some time teh address is printed in 32 bit only as below
this=0x6787e0
any reason why this is happening?
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Jan 16, 2014
whats wrong with this code, I'm trying to parse a .js file and replace all the ";" with "; " i.e add a new line after each ";". So I load the file into a char[] buffer then assign a string to this contents of this buffer. Then loop char by char through using an iterator and check for a ";", if found use replace. So int i gets to about 85898 then crashes with unknown error, 'i' should reach about 175653. It does work up till it crashes. And, is this not a simpler way to load a file into a buffer, there is in C.
Code:
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#include <fstream>
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int main()
[code]....
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Jul 16, 2013
Notes: Im Using SDL, Im using Codeblocks to code
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fatal signal segmentation fault (sdl parachute deployed)
Inside my code, I created a malloce function that checks malloc for me ( so i dont have to do it )
( general.h )
void* malloce ( size_t size )
{
printf ( "start malloce %i
", size );
[Code]....
funny thing is that i called this malloce function about 20 times before it hits this part of the code, it is unknown behavior to me!
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Nov 6, 2012
I have a function such that one of its parameters is a 2D array of type int. The parameter is defined as follows:
[code]
int topoGraph [][MAX_VERTICES]
[code]
However, the following code snippet from the body of the function crashes at the specified line:
Code :
if( counter >= 4 && !adjMatrixAlreadySet) {
if( edgeCost == 10 ) {
topoGraph[srcVertex][dstVertex] = 1; <<<<<---------- The point of crash
}
else if( edgeCost == 100000 )//restricted link {
topoGraph[srcVertex][dstVertex] = edgeCost;
[code]....
It seems like there is an undefined behaviour at the specified point of crash since it crashes with different values of srcVertex and dstVertex each time I run it.
What might be the reason for this crash ?
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Nov 26, 2012
Why I get a crash when initializing the indices array below (bottom)-
Code:
struct TerrainGroupData {
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[Code] ...
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Oct 24, 2014
This function is apparently causing infinite recursion, but I have no clue what's causing it:
Code:
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Feb 17, 2014
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May 10, 2013
I am new to C. I've been trying to use C to code some statistical functions originally coded in R. I've encountered an interesting phenomenon. In the function foo1, I declared the array v1v2b using an actual value 1999000. The function runs fine when I call it in R.
Code:
void foo1(double *x, double *y, int *nsamp){
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Code:
void foo2(double *x, double *y, int *nsamp){
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[Code] .....
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Dec 13, 2013
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Oct 30, 2014
while(!secList.empty()){
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[code]....
my program crash when it try to assign the return value of the function to the local value. extract function does return correct value, but it just crash when done executing.
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Oct 18, 2014
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Code:
int main() {
WSADATA wsaData;
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[Code] ....
Debug crash code:
Code:
First-chance exception at 0x00161831 in ConsoleApplication1.exe: 0xC0000005: Access violation reading location 0x0000000C.
Unhandled exception at 0x00161831 in ConsoleApplication1.exe: 0xC0000005: Access violation reading location 0x0000000C.
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Nov 29, 2014
What happens if I make a server application using tcp protocol and then establish connection with a client application but the server crash and then the client send data. Will the data be lost or the system will continue trying to send it?
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May 9, 2012
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Mar 24, 2013
So here is the C code:
Code:
#include <stdio.h>
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[code]....
The array is not filled incorrectly for some reason, more specifically the first row.The first two cycles of the for loop seem to work correctly. One if the bugs seems to occur on the third. when array[0][2] is filled with number 7, for some reason array[1][0] changes it value to 7 as well.
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Jul 2, 2014
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Mar 21, 2013
I'm writing a program with a class containing a private std::vector<bool>. I chose bool because the vector represents a 2D array (think grid) and I only need 2 states per cell. I kept it one-dimensional as this hardly complicates things.
My problem is that I don't know how to initialize the vector, i.e. fill it with 0's.
The grid's resolution is not known at compile time, so I imagine I have to set the size (and content) of the vector in the class constructor.
Here's what I have tried among several things:
Code: World::World(const u_short worldsize)
{
grid.reserve(worldsize * worldsize); // grid is the private vector; square dimensions.
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std::cout << grid.size();
} The output is 0. Only std::vector::push_back seems to have an effect on size(), but judging by its description, it doesn't look like the right candidate to populate a vector with zeros. Correct me if I'm wrong.
Frankly I expected line 3 to set the vector's size.
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Jun 25, 2013
I have this snippet :
Code:
#include<stdio.h>
#define LEN 3
int main(void)
{
int a[LEN] = {0} , b[LEN] = {0} , i = 0;
[Code] ....
/* OUTPUT :
a[0] = 2 , b[0] = 1
a[1] = 0 , b[1] = 3
a[2] = 0 , b[2] = 0 */
The problem is some elements of the array would be remained zero and unused. Is there any solution about this wasting of memory?
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Mar 24, 2013
Assuming that we have :
Code:
int arr2d[rows][columns] ; // Not valid syntax of course ... let be arr2d rows * columns size
for(int i=0; i<rows; i++)
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Oct 6, 2013
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Code:
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Feb 1, 2013
How to fill a vector with structs that are read in from a separate file. Each line in the file would read for example "Doe John M 26" for the name of the person, gender and age. I just need to get pointed in the right direction so I can get this started.
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Jun 20, 2013
I am having a trivial trouble on how to create three different arrays from a text file. I am a beginner in C++. I have a .txt file containing a string of 'float' values as below:
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0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
//----------------------
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p2[] has elements from line: 2, 5, 8, .., and
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My original file has a huge amount of data, so I would have to use a loop, but I cannot think of a way to fill my arrays as described.
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May 22, 2014
I have a vector that I want to use to source another vector, something like copy_if, but without the need to allocate space first:
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std::vector< int > numbers = { 1, 2, 3, 4, 5, 6 };
std::vector< int > odd_numbers;
std::sweet_function( numbers.begin(), numbers.end(), odd_numbers, is_odd );
// odd_numbers is { 1, 3, 5 }
Even better might be a std::transform_if
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