Is there something that I can do in C and not in C++?

[renu434]

Is there something that I can do in C and not in C++?

[AdrianH]

Is there something that I can do in C and not in C++?

Spell its name with a single character. :D

C++ is a superset of C (more or less, less now that C99 is out). C99 has a bunch of things that C++ cannot do, such as specifying initialisation elements:

struct A {
  int a;
  char b;
  int c;
};
 
struct A obj = { b = 'd' };
 

That is valid using the new C standard (called C99). It is not valid in C++.

Variable arguments for macros is another one.

Those are two of the most prominent difference I've found. There are undoubtedly others. Check out the difference by looking up C99 on the web. If I'm not mistaken, C++ is a true superset of C89. I could be wrong though.


Adrian

[Motoma]

Haha, when I read this I could not believe it. I had to fire up g++ and test out for myself that this would not work in C++. Thanks for the post AdrianH!

Spell its name with a single character. :D

C++ is a superset of C (more or less, less now that C99 is out). C99 has a bunch of things that C++ cannot do, such as specifying initialisation elements:

struct A {
  int a;
  char b;
  int c;
};
 
struct A obj = { b = 'd' };
 

That is valid using the new C standard (called C99). It is not valid in C++.

Variable arguments for macros is another one.

Those are two of the most prominent difference I've found. There are undoubtedly others. Check out the difference by looking up C99 on the web. If I'm not mistaken, C++ is a true superset of C89. I could be wrong though.


Adrian

[AdrianH]

Haha, when I read this I could not believe it. I had to fire up g++ and test out for myself that this would not work in C++. Thanks for the post AdrianH!

What? You didn't know that C could spell its own name with a single letter? :D

Actually I think it should have been:

      struct A {
        int a;
        char b;
        int c;
      };
 
      struct A obj = { .b = 'd', .c = 5 };

Note the '.' before b = 'd'. Also seperation between is using a comma, not a semicolon.


Adrian

[JosAH]

C++ is a true superset of C89. I could be wrong though.

No it isn't. The widening promotions are different in C (both C89 and C99). e.g.
a char will be an int when passed as a parameter to a function that takes a
variable number of arguments in C; it will be a char in C++ though ...

but I agree: the differences are minor (but essential).

kind regards,

Jos

[AdrianH]

No it isn't. The widening promotions are different in C (both C89 and C99). e.g.
a char will be an int when passed as a parameter to a function that takes a
variable number of arguments in C; it will be a char in C++ though ...

but I agree: the differences are minor (but essential).

kind regards,

Jos

True. Forgot about that one.


Adrian

[weaknessforcats]

struct A obj = { obj.b = 'd' };
 

works in C++.

[AdrianH]

struct A obj = { obj.b = 'd' };
 

works in C++.

WOW, it is surprising that it compiles (without warnings I might add with full warnings enabled). What is not as surprising is that it doesn't work. ;)

Try this code:

#include <stdio.h>
int main() {
      struct A {
        int a;
        char b;
        int c;
      };
 
      struct A obj = { obj.b = 'd', obj.c = 5 };
 
      printf("%d, %c, %d\n", obj.a, obj.b, obj.c);
      return 0;
}

No compile error, but doesn't work either (at least not under g++ with only -Wall switch).


Adrian

[weaknessforcats]

Yeah. No warnings but it doesn't work in Visual Studio.NET.2005 either. Previously, I just reported on th basis of no compiler messages.