convert int to C string

[Andrej Viktorovich]

Hello,

Moving from delphi to C

Got garbage on output while converting integer to C string. Have feeling that something wrong with char* on intToStr return. What is the right way of doing that?

char* intToStr(int value)
{
char buffer[33];
char* c;
c= itoa(value,buffer,10);
return buffer;
}

int _tmain(int argc, _TCHAR* argv[])
{

cout<<intToStr(55)<<"\n";

getc(stdin);

return 0;
}

Thank you

 

[Alain Ketterlin]

Moving from delphi to C

Sorry, this group is about C++. Try other, more relevant newsgroups.

Got garbage on output while converting integer to C string. Have
feeling that something wrong with char* on intToStr return. What is
the right way of doing that?

char* intToStr(int value)
{
char buffer[33];
char* c;
c= itoa(value,buffer,10);
return buffer;
}

You can't return a pointer to a local array: the storage for the array
disappears at the end of the call.

-- Alain.

 

[Andrej Viktorovich]

You can't return a pointer to a local array: the storage for the array
disappears at the end of the call.

So only way is to create char[] in main method and pas it to function that makes conversion from integer to string?

Thank you

 

[Victor Bazarov]

You can't return a pointer to a local array: the storage for the array
disappears at the end of the call.

So only way is to create char[] in main method and pas it to function that makes conversion from integer to string?

No, in C++ there are other ways. Try our FAQ, maybe section 39, and
*definitely* section 5. http://www.parashift.com/c++-faq-lite/

V

 

[BGB]

Sorry, this group is about C++. Try other, more relevant newsgroups.

noting that he was using 'cout' in the snipped portion, means it was C++
anyways...

kind of funny that some of the first responses on the C newsgroup were
"this code is C++, not C".

Got garbage on output while converting integer to C string. Have
feeling that something wrong with char* on intToStr return. What is
the right way of doing that?

char* intToStr(int value)
{
char buffer[33];
char* c;
c= itoa(value,buffer,10);
return buffer;
}

You can't return a pointer to a local array: the storage for the array
disappears at the end of the call.

yep, some other means would be needed to return the string.

there are simple ways to deal with this using the static keyword, but
many regard this as "evil", and is not thread-safe, ...

other options include specialized allocators, using heap allocated
memory, ...

or, possibly, something like std::string or similar.

 

[Kevin McCarty]

Hello,

Moving from delphi to C

Actually it would appear you're moving to C++, given the use of "cout"
in your code sample.

Got garbage on output while converting integer to C string. Have feeling that something wrong with char* on intToStr return. What is the right way of doing that?

char* intToStr(int value);

// ...

int _tmain(int argc, _TCHAR* argv[])
{

        cout<<intToStr(55)<<"\n";

  getc(stdin);

  return 0;
}

Assuming a C++ 2011 compiler, try:

#include <string>
#include <iostream>

int main()
{
using std::cout;
using std::endl;
cout << std::to_string(55) << endl;
return 0;
}

Otherwise, if you can use Boost, use

#include <boost/lexical_cast.hpp>
// ...
cout << boost::lexical_cast<std::string>(55) << endl;

Otherwise, use a stringstream:

#include <sstream>
// ..
std:stringstream s;
s << 55;
cout << s.str() << endl;


I'm assuming that the streaming of the string result to std::cout was
just for illustrative purposes. If all you need to do is actually to
print an integer to stdout (or other stream), you can just give the
literal 55 directly to the stream:

cout << 55 << endl;


- Kevin B. McCarty

 

[Nobody]

You can't return a pointer to an *automatic* array (for that reason).

So only way is to create char[] in main method and pas it to function that
makes conversion from integer to string?

You can return a pointer to a static array, e.g.:

char* intToStr(int value)
{
static char buffer[33];
char* c = itoa(value,buffer,10);
return buffer;
}

but that isn't re-entrant, and you'll need to have finished using the
returned pointer before the next call to intToStr().

You can return a pointer to dynamically-allocated memory, e.g.:

char* intToStr(int value)
{
char* buffer = malloc(33);
char* c = itoa(value,buffer,10);
return buffer;
}

but then the caller has to explicitly free() the memory.

In C, having the caller pass in a suitably-sized buffer is usually the way
to go, so long as the caller can determine what is a suitable size without
too much effort.

In C++, you'd normally use a std::string rather than a char* (you can
then use the .c_str() method to get a char* for the data), e.g.:

std::string intToStr(int value)
{
std:stringstream os;
os << value;
return out.str();
}

 

[Bo Persson]

Andrej Viktorovich skrev 2012-06-29 14:43:

Hello,

Moving from delphi to C

Got garbage on output while converting integer to C string. Have feeling that something wrong with char* on intToStr return. What is the right way of doing that?

char* intToStr(int value)
{
char buffer[33];
char* c;
c= itoa(value,buffer,10);
return buffer;
}

int _tmain(int argc, _TCHAR* argv[])
{

cout<<intToStr(55)<<"\n";

getc(stdin);

return 0;
}

If this is C++, you don't have to do anything at all. Just output the value:

int _tmain(int argc, _TCHAR* argv[])
{

cout << 55 << "\n";

getc(stdin);

return 0;
}


Too easy?


Bo Persson