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Lies in education [was Re: The "loop and a half"]


On Thu, 12 Oct 2017 02:43 am, Marko Rauhamaa wrote:

> Chris Angelico <rosuav at gmail.com>:
> 
>> The places where C++ is not a superset of C are mostly things you
>> wouldn't want to be doing anyway. You can generally take C code and
>> compile it with a C++ compiler, and it'll have the same semantics.
> 
> Here's a C/C++ program:
> 
> ========================================================================
> #include <stdio.h>
> 
> int main()
> {
>     struct {} s;
>     printf("%d\n", (int) sizeof 'a');
>     printf("%d\n", (int) sizeof s);
>     return 0;
> }
> ========================================================================
> 
> When compiled (with gcc) as a C program, the output is:
> 
>     4
>     0
> 
> When the same program is compiled (with gcc) as a C++ program, the
> output is:
> 
>     1
>     1
> 
> That is not immediately all that significant but points to subtle
> incompatibilities between the data models of C and C++.

I don't think anyone should expect that platform specific details like the
size of a char should be precisely the same between C and C++. Even two
different C compilers could return different values.



> Then we have syntactic problems:
[...]

I don't believe that anyone meant to imply that C++ is an exact superset of C.
I know I didn't, although I acknowledge that my terminology was lazy.

C++ is broadly-speaking compatible with C, with just enough differences to act
as landmines to the unwary. Good enough?




-- 
Steve
?Cheer up,? they said, ?things could be worse.? So I cheered up, and sure
enough, things got worse.