pointers, structures, and malloc

**lugnut** · 10-08-2008

I switched compilers on a lark. I've gotten rid of my error messages. I have this code:

Code:

  struct sdata_2 {
      char d21;
      char d22;
      char d23;
      char d24;
      char d2x[20];

     struct sdata_2 sdata2 = { 'a',  'b', 'c', 'd', 'Mike' }

The compiler is very upset over Mike. It does not like multi-byte initial values. Since d2x is defined as a string of bytes, how do I get an initial value?

TIA

**matsp** · 10-08-2008

try using a string rather than a multibyte character (which possibly would match an integer type, but certainly not a string):

Code:

struct sdata_2 sdata2 = { 'a',  'b', 'c', 'd', "Mike" }

--
Mats

**tabstop** · 10-08-2008

char is a single character, so 'use these'. char[20] is a bunch of characters, so "use these". The added advantage of the string is that it is properly null-terminated for you.

**~~master5001~~** · 10-08-2008

I assume that the missing '}' in the above is just a copy and paste error, too.

**Elysia** · 10-09-2008

Originally Posted by lugnut

The compiler is very upset over Mike. It does not like multi-byte initial values. Since d2x is defined as a string of bytes, how do I get an initial value?

TIA

The problem is that 'Mike' is an integer, aka int. 'Mike' is 'M' + 'i' + 'k' + 'e' (or some variant, not sure), which certainly does not fit into a char.
Double quotes, on the other hand, is an array of chars, so it fits where single quotes does not.

**zacs7** · 10-09-2008

> The problem is that 'Mike' is an integer, aka int. 'Mike' is 'M' + 'i' + 'k' + 'e' (or some variant, not sure), which certainly does not fit into a char.
Simpler than that. It's syntactically invalid

> Double quotes, on the other hand, is an array of chars
is a nul-terminated array of chars
Very, Very, Very, Important

Just remember, anything within single quotes must evalute to a single byte. Which of course has an integer value.

**Elysia** · 10-09-2008

Originally Posted by zacs7

> The problem is that 'Mike' is an integer, aka int. 'Mike' is 'M' + 'i' + 'k' + 'e' (or some variant, not sure), which certainly does not fit into a char.
Simpler than that. It's syntactically invalid

Are you sure?

Code:

#include <iostream>

using namespace std;

int __cdecl main()
{
	unsigned int x = '1234';
	cout << "0x" << hex << x << endl;
}

0x31323334

**zacs7** · 10-09-2008

Code:

[zac@neux ~]$ cat ln.c 
#include <stdio.h>

int main(void)
{
   unsigned int a = '1234';
   unsigned int b = '1' + '2' + '3' + '4';

   printf("&#37;X & %u\n", a, a);
   printf("%X & %u\n", b, b);
   return 0;
}
[zac@neux ~]$ gcc -Wall -pedantic -std=c89 ln.c -o ln
ln.c:5:12: warning: multi-character character constant
[zac@neux ~]$ ./ln 
31323334 & 825373492
CA & 202

Turns out I was wrong :P. I wonder what it means then?

**robwhit** · 10-09-2008

Undefined behavior!!!! %X with an int! should be an unsigned int!! woop! *siren sounds*

I'm gonna go do something else for a while.

**tabstop** · 10-09-2008

Originally Posted by zacs7

Code:

[zac@neux ~]$ cat ln.c 
#include <stdio.h>

int main(void)
{
   unsigned int a = '1234';
   unsigned int b = '1' + '2' + '3' + '4';

   printf("%X & %u\n", a, a);
   printf("%X & %u\n", b, b);
   return 0;
}
[zac@neux ~]$ gcc -Wall -pedantic -std=c89 ln.c -o ln
ln.c:5:12: warning: multi-character character constant
[zac@neux ~]$ ./ln 
31323334 & 825373492
CA & 202

Turns out I was wrong :P. I wonder what it means then?

Conveniently, '1' is 0x31, '2' is 0x32, '3' is 0x33, and '4' is 0x34

Thread: pointers, structures, and malloc

Thread Tools

Search Thread

Display

Switch to Bloodshed

Similar Threads

malloc, structures, arrays and sudoku!!

Structures, arrays, pointers, malloc.

pointers and structures

returning an array of pointers to structures

Freeing pointers in structures