Author: Dann Corbit
Date: 20:09:13 02/28/03
Go up one level in this thread
On February 28, 2003 at 10:48:19, Matt Taylor wrote:
>On February 27, 2003 at 09:55:35, Tom Likens wrote:
>
>>On February 26, 2003 at 17:07:45, Bo Persson wrote:
>>
>>[--snip--]
>>
>>
>>>>I see that I did not include data.h in data.c but it caused me no problem
>>>>with c files
>>>
>>>You have found an actual difference between the languages!
>>>
>>>In C++, const variables are considered local unless declared otherwise. In C,
>>>all global (file level) variables are extern by default.
>>>
>>>Bo Persson
>>>bop2@telia.com
>>
>>
>>No, no- C++ is just a superset of C. There is *absolutely*
>>no differences between them :-) :-) :-) :-) :-) ;-)
>>
>>regards,
>>--tom
>
>Actually there are many subtle differences. Here's an example:
>
>C:
>int *array;
>array = malloc(size);
>
>C++:
>int *array;
>array = malloc(size); // error
>array = (int *) malloc(size);
>array = new int[size]; // preferred
>
>Also, I have a fair amount of code that looks like this:
>
>char *byteptr;
>
>// some stuff
>if (blah)
> x = *((int *) byteptr)++;
>else
> x = (int) *byteptr++;
>
>This does not work in C++. This example actually came from an x86 disassembler I
>wrote where it was extremely convenient to break type rules again & again. The
>only solution I have found in C++ is to use a union with pointers of varying
>type.
>
>You are right that most of C and C++ is the same, but some acceptable C programs
>will not compile as C++ for various reasons.
I think the smileys are a clue that he knew.
size_t s = sizeof('a'); // different answers for C and C++
const int n = 5; int a[n]; // Fails in C, works in C++
int new = 5; // fine in C, but keyword collision in C++
int main()
{
int i;
i = 5;
int j; /* Legal in C++, Illegal in C */
return 0;
}
An example from Daniel Hudson:
#include <stdio.h>
#include <stdlib.h>
int *array1, array2[10];
const int age = 24; /* static in C++, but extern in C */
struct a {
struct b { int c; }
int d;
}
struct f { int a1; };
typedef double f; /* legal C, illegal C++ */
int *array1; /* duplicate defintion error in C++ */
int main(void)
{
static struct array2 {int x;}; /* storage class specifier *
* illegal in C++, ignored in C */
struct b B; /* legal C, illegal it is local to type struct a *
* in C++. */
char str[5] = "abcdef"; /* valid C, not valid C++, array overflow */
array1 = malloc(10); /* implicit cast in C, illegal in C++ */
printf("sizeof(array2) = %s\n" sizeof(array2));
/* in C struct array2 will NOT hide previous definition of array2,
in C++ it will. */
return 0;
}
etc.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.