Chris Angelico <ros...@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++.
Then we have syntactic problems:
========================================================================
int main()
{
void *s = "hello";
char *t = s;
return 0;
}
========================================================================
which, as a C program, makes gcc perfectly happy, but a C++ compilation
complains:
test.C: In function ‘int main()’:
test.C:5:15: error: invalid conversion from ‘const void*’ to ‘void*’ \
[-fpermissive]
void *s = "hello";
^~~~~~~
test.C:6:15: error: invalid conversion from ‘void*’ to ‘char*’ [-fper\
missive]
char *t = s;
^
(The first one should trigger an error message even in C compilation,
but string literals were standardized to be "semiconstant" in C.)
Marko
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