Is this right to do so

Question

4.20/5 (5 votes)

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I am quite puzzled by the code below:

char *pchar=new char[2];
pchar[0]=4;
...
int t=pchar[0];

for(int i=0;i<t;t;i++)>
  do sth.
...

pchar[0] is a char, can it be compared with an integer without any previous
action? Is it safe to do so?

Posted 24-Apr-11 2:02am

solesonglei

Updated 25-Apr-11 2:01am

thatraja

v2

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Comments

Albert Holguin 24-Apr-11 19:00pm

not sure why this was voted down, its a legitimate question, my 5

solesonglei 24-Apr-11 23:47pm

thanks for Albert,I'll pay more attention on my question

3 solutions

Solution 1

No, this is not safe or even reasonable code. If you wanted an array of int's, you should have said new int[2] instead of new char[2].

However, having said that, you can convert a char to an int, although the compiler might complain; it would be better to cast the char to an int.

Posted 24-Apr-11 2:47am

Hans Dietrich

Updated 24-Apr-11 4:01am

v2

Comments

solesonglei 24-Apr-11 9:36am

I see ,thx.

Albert Holguin 24-Apr-11 18:59pm

there's a big difference in new int[2] versus new char[2], 6 bytes worth... people commonly use char's to handle 8bit data, may not be the best practice, but it is common

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CPallini · Accepted Answer · 2011-04-24T06:34:00

Solution 3

Yes, you may assign a char to an int (a char is a signed int 8-bit wide, the promotion to a wider integer type, like int, happens automatically and without complains). It is a bit unusual (and you don't really need it, in the posted example), but there's nothing wrong in that.
:-)

Posted 24-Apr-11 6:34am

CPallini

Comments

Albert Holguin 25-Apr-11 10:25am

Not that unusual actually... my 5

CPallini 26-Apr-11 3:18am

Yes, we 'embedded' people, after all, exist.

mbue · Accepted Answer · 2011-04-24T03:04:00

Solution 2

This depends on the action you want to do:
char type is signed therefore you get negative int, for example "©"==-87.
better you cast:

int t=(int)(unsigned char)pchar[0];

Regards.

Posted 24-Apr-11 3:04am

mbue