why does it crash?

**Victor Bazarov** · Jul 19 '05, 07:07 PM

Re: why does it crash?

"Developwebsite s" <developwebsite s@aol.combatSPA M> wrote...[color=blue]
> this program compiles, but crashes when run.
> whats wrong with it?
>
> #include<iostre am.h>
> #include<iomani p.h>
>
> int numb_cities=0;
> const int MAX = 120;
>
> class Cities {
> private:
> char cityname[MAX][MAX];//an array of 120 cities.
> int temp[MAX];
>
> public:
> void input();
> void output();
> void sort();
> };
>
>
> void Cities::input()
> {
> char y_n;
> do{
> cout<<"\n\n";
> cout<<"Please enter name of city#"<<numb_ci ties+1<<": ";
> cin>>cityname[numb_cities];
> cout<<"\nPlease enter "<<cityname[numb_cities]<<"'s temp: ";
> cin>>temp[numb_cities];
> numb_cities++;
> cout<<"\nAnothe r city?(Y/N)";
> cin>>y_n;
> }while(y_n =='y' || y_n =='Y');
> cout<<"\n\n";
> }
>
> void Cities::output( )
> {
> cout<<"\n"<<"na me of city"
> <<" temperature"
> <<"\n";
> for(int t=0;t<numb_citi es;t++)
> {
> cout<<setw(5)<< cityname[t]<<setw(15)<<tem p[t]<<"\n";
> }
> }//close output
>
> void Cities::sort()
> {
> char citynametemp[MAX][MAX];[/color]

When declaring an array of MAX by MAX size, you have to remember
that indices of the elements of the array only go from 0 to MAX-1.

[color=blue]
> int tempt;
> for(int a=0;a<numb_citi es;a++) {
> for(int b=a+1; b<numb_cities;b ++) {
> if (temp[a]<temp[b]) {
> tempt = temp[a];
> temp[a] = temp[b];
> temp[b] = tempt;
> citynametemp[MAX][MAX] = cityname[a][MAX];[/color]

There is no element with index [MAX][MAX] in the array 'citynametemp',
as there isn't an element with any index [MAX] in any array of size
'MAX'. The index spans from 0 to MAX-1.

Now, you're trying to copy the contents of 'cityname[a]' to
'citynametemp[a]'. You should probably use memcpy() for that:

memcpy(cityname temp[a], cityname[a], MAX);

and not the assignment.

[color=blue]
> cityname[a][MAX] = cityname[b][MAX];
> cityname[b][MAX] = citynametemp[MAX][MAX];
> }//close if
> }//close b loop
> }//close a loop
> }//close sort
>
>
> int main()
> {
> Cities info;
>
> info.input();
> info.output();
> info.sort();
> info.output();
> return 0;
> }
> --------------------------------------------------
> remove *batSPAM* to e-mail me
> --------------------------------------------------[/color]

HTH

Victor

**Moonlit** · Jul 19 '05, 07:07 PM

Re: why does it crash?

Hi,

Could you be more specific at which line it crashes, I compiled it and it
runs for me (that doesn't say it is correct though).

BTW Using vectors and STL stuff would have reduced your code to a few lines.
To get some ideas:

#include <algorithm>
#include <string>

using namespace std;

class CCityInfo
{
string CityName;
int Temp;
// Constructor stuff and init etc public keywords Get and Put functions
etc..
bool operator <( const CCityInfo& City1 ) const
{
return Temp < City1.Temp;
}
};
vector<CCityInf o> Cities;

sort( Cities.begin(), Cities.end() );

-------------------------------------------------------
[root@moonlit root]# ./r

Please enter name of city#1: 1

Please enter 1's temp: 2

Another city?(Y/N)y

Please enter name of city#2: 3

Please enter 3's temp: 2

Another city?(Y/N)n

name of city temperature
1 2
3 2

name of city temperature
1 2
3 2
------------------------------------------------------------

"Developwebsite s" <developwebsite s@aol.combatSPA M> wrote in message
news:2003101015 0519.17356.0000 0063@mb-m03.aol.com...[color=blue]
> this program compiles, but crashes when run.
> whats wrong with it?
>
> #include<iostre am.h>
> #include<iomani p.h>
>
> int numb_cities=0;
> const int MAX = 120;
>
> class Cities {
> private:
> char cityname[MAX][MAX];//an array of 120 cities.
> int temp[MAX];
>
> public:
> void input();
> void output();
> void sort();
> };
>
>
> void Cities::input()
> {
> char y_n;
> do{
> cout<<"\n\n";
> cout<<"Please enter name of city#"<<numb_ci ties+1<<": ";
> cin>>cityname[numb_cities];
> cout<<"\nPlease enter "<<cityname[numb_cities]<<"'s temp: ";
> cin>>temp[numb_cities];
> numb_cities++;
> cout<<"\nAnothe r city?(Y/N)";
> cin>>y_n;
> }while(y_n =='y' || y_n =='Y');
> cout<<"\n\n";
> }
>
> void Cities::output( )
> {
> cout<<"\n"<<"na me of city"
> <<" temperature"
> <<"\n";
> for(int t=0;t<numb_citi es;t++)
> {
> cout<<setw(5)<< cityname[t]<<setw(15)<<tem p[t]<<"\n";
> }
> }//close output
>
> void Cities::sort()
> {
> char citynametemp[MAX][MAX];
> int tempt;
> for(int a=0;a<numb_citi es;a++) {
> for(int b=a+1; b<numb_cities;b ++) {
> if (temp[a]<temp[b]) {
> tempt = temp[a];
> temp[a] = temp[b];
> temp[b] = tempt;
> citynametemp[MAX][MAX] = cityname[a][MAX];
> cityname[a][MAX] = cityname[b][MAX];
> cityname[b][MAX] = citynametemp[MAX][MAX];
> }//close if
> }//close b loop
> }//close a loop
> }//close sort
>
>
> int main()
> {
> Cities info;
>
> info.input();
> info.output();
> info.sort();
> info.output();
> return 0;
> }
> --------------------------------------------------
> remove *batSPAM* to e-mail me
> --------------------------------------------------[/color]

**Xenos** · Jul 19 '05, 07:07 PM

Re: why does it crash?

"Developwebsite s" <developwebsite s@aol.combatSPA M> wrote in message
news:2003101015 0519.17356.0000 0063@mb-m03.aol.com...[color=blue]
> this program compiles, but crashes when run.
> whats wrong with it?
>
> #include<iostre am.h>
> #include<iomani p.h>
>
> int numb_cities=0;
> const int MAX = 120;
>
> class Cities {
> private:
> char cityname[MAX][MAX];//an array of 120 cities.
> int temp[MAX];[/color]

Why do people still insist on writing code that can buffer overrun???
One (maybe two?) word: std::string
[color=blue]
>
> public:
> void input();
> void output();
> void sort();
> };
>
>
> void Cities::input()
> {
> char y_n;
> do{
> cout<<"\n\n";
> cout<<"Please enter name of city#"<<numb_ci ties+1<<": ";
> cin>>cityname[numb_cities];
> cout<<"\nPlease enter "<<cityname[numb_cities]<<"'s temp: ";
> cin>>temp[numb_cities];
> numb_cities++;
> cout<<"\nAnothe r city?(Y/N)";
> cin>>y_n;
> }while(y_n =='y' || y_n =='Y');
> cout<<"\n\n";
> }[/color]

see above

[color=blue]
>
> void Cities::output( )
> {
> cout<<"\n"<<"na me of city"
> <<" temperature"
> <<"\n";
> for(int t=0;t<numb_citi es;t++)
> {
> cout<<setw(5)<< cityname[t]<<setw(15)<<tem p[t]<<"\n";
> }
> }//close output
>
> void Cities::sort()
> {
> char citynametemp[MAX][MAX];
> int tempt;
> for(int a=0;a<numb_citi es;a++) {
> for(int b=a+1; b<numb_cities;b ++) {
> if (temp[a]<temp[b]) {
> tempt = temp[a];
> temp[a] = temp[b];
> temp[b] = tempt;
> citynametemp[MAX][MAX] = cityname[a][MAX];
> cityname[a][MAX] = cityname[b][MAX];
> cityname[b][MAX] = citynametemp[MAX][MAX];[/color]

you cannot move char array strings around using the assignment operator.

[color=blue]
> }//close if
> }//close b loop
> }//close a loop
> }//close sort
>
>
> int main()
> {
> Cities info;
>
> info.input();
> info.output();
> info.sort();
> info.output();
> return 0;
> }
> --------------------------------------------------
> remove *batSPAM* to e-mail me
> --------------------------------------------------[/color]

**Default User** · Jul 19 '05, 07:07 PM

Re: why does it crash?

Xenos wrote:
[color=blue]
> Why do people still insist on writing code that can buffer overrun???
> One (maybe two?) word: std::string[/color]

The idiot has been told this many times. He reacted so poorly to past
advice that he landed in my killfile.

Brian Rodenborn

**Developwebsites** · Jul 19 '05, 07:07 PM

Re: why does it crash?

>> Why do people still insist on writing code that can buffer overrun???[color=blue][color=green]
>> One (maybe two?) word: std::string[/color]
>
>
>The idiot has been told this many times. He reacted so poorly to past
>advice that he landed in my killfile.
>[/color]

you are the one who is an idiot. I have said on numerous occassions that we
havent covered std:: or vectors yet in class, therefore I cannot and will not
use them eventhough I know how to.

read people's posts next time and answer the question asked, instead of making
yourself look smart in this ng.

--------------------------------------------------
remove *batSPAM* to e-mail me
--------------------------------------------------

**Jerry Coffin** · Jul 19 '05, 07:08 PM

Re: why does it crash?

In article <20031010150519 .17356.00000063 @mb-m03.aol.com>,
developwebsites @aol.combatSPAM says...[color=blue]
> this program compiles, but crashes when run.
> whats wrong with it?[/color]

Quite a bit, if you'll pardon my being a bit blunt about it.
[color=blue]
> #include<iostre am.h>
> #include<iomani p.h>[/color]

For standard code, you want <iostream> and <iomanip>. I'd suggest
adding <vector> and <string> as well.
[color=blue]
> int numb_cities=0;[/color]

I don't think this should be a global.
[color=blue]
> const int MAX = 120;[/color]

And I don't think you should have this here at all.
[color=blue]
>
> class Cities {
> private:
> char cityname[MAX][MAX];//an array of 120 cities.
> int temp[MAX];
>
> public:
> void input();
> void output();
> void sort();
> };[/color]

I think you should break things down a bit differently -- Cities isn't a
very good class, IMO. I'd think about having City as a class, and then
creating an array (or better yet, a vector) of City objects, with
(perhaps) a bit of extra code to manage the collection as a whole. If
City is well defined, however, the latter often becomes quite trivial.
[color=blue]
> void Cities::input()
> {
> char y_n;
> do{
> cout<<"\n\n";
> cout<<"Please enter name of city#"<<numb_ci ties+1<<": ";
> cin>>cityname[numb_cities];[/color]

When you declare cityname[numb_cities], that means the valid subscripts
run from 0 through (numb_cities-1). Right here you're trying to read
data into cityname[numb_cities], which results in undefined behavior.
[color=blue]
> cout<<"\nPlease enter "<<cityname[numb_cities]<<"'s temp: ";
> cin>>temp[numb_cities];[/color]

Here you're doing pretty much the same thing. What it looks to me like
you want to do is something like:

for (i=0;i<numb_cit ies;i++)
// leaving out the prompts and such for now...
cin >> cityname[i];
cin >> temp[i];
}

As I said before, however, I'd define City as a class, so you'd have
something like this:

class City {
std::string name;
int temp;

public:

void read() {
std::cout << "Please enter city name: ";
std::readline(s td::cin, name);
std::cout << "Please enter temperature: ";
std::cin >> temp;
}
};

class cities {
std::vector<Cit y> citynames;
public:

void read() {
do {
City x;
x.read();
citynames.push_ back(x);
std::cout << "Another City?(Y/N)";
std::cin >> y_n;
while (std::tolower(y _n) == 'y');
}
};

Now cities only deals with storing data for as many cities as the user
enters, and leaves it to each individual City to read its own data.
[color=blue]
> void Cities::output( )
> {
> cout<<"\n"<<"na me of city"
> <<" temperature"
> <<"\n";
> for(int t=0;t<numb_citi es;t++)
> {
> cout<<setw(5)<< cityname[t]<<setw(15)<<tem p[t]<<"\n";
> }
> }//close output[/color]

Again, each City should know how to display its own data, and the cities
collection should only deal with having each City in the collection
display itself.
[color=blue]
> void Cities::sort()[/color]

std::vector (as well as all the other standard collections) can be
sorted without your writing a lousy sort routine for the ten billionth
time.

--
Later,
Jerry.

The universe is a figment of its own imagination.

why does it crash?

why does it crash?

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