fork download

copy

/* A bunch of code that compiles and runs under C89 but fails under any C++ 
 *
 *
 * Ryan Haining
 * Source may be redistributed freely for educational purposes as long as it
 * contains this notice.
 * If you're redistributing for commerical purposes, err, you may want to
 * rethink that decision.
 */
 
/* type aliases and struct names occupy separate namespaces in C, not in C++ */
struct S { int i; };
typedef int S;
 
 
struct Outer { struct Inner { int i; } in; };
/* struct Inner will be Outer::Inner in C++ due to name scope */
struct Inner inner;
 
 
/* default return type of int in C, C++ functions need explicit return types */
g() {
    return 0;
}
 
 
/* C sees this as two declarations of the same integer,
 * C++ sees it as redefinition */
int n;
int n;
 
 
/* K&R style argument type declarations */
void h(i) int i; { }
 
 
/* struct type declaration in return type */
struct S2{int a;} j(void) { struct S2 s = {1}; return s; }
 
 
/* struct type declaration in argument, stupid and useless, but valid */
/*void dumb(struct S3{int a;} s) { } */
 
 
/* enum/int assignment */
enum E{A, B};
enum E e = 1;
 
 
void k() {
    goto label; /* C allows jumping past an initialization */
    {
        int x = 0;
label:
        x = 1;
    }
}
 
 
/* () in declaration means unspecified number of arguments in C, the definition
 * can take any number of arguments,
 * but means the same as (void) in C++  (definition below main) */
void f();
 
int main (void) {
    f(1); /* doesn't match declaration in C++ */
    {
        /* new is a keyword in C++ */
        int new = 0;
    }
 
    /* no stdio.h include results in implicit definiton in C.  However,
     * as long as a matching function is found at link-time, it's fine.
     * C++ requires a declaration for all called functions */
    puts("C is not C++");
 
    {
        int *ip;
        void *vp = 0;
        ip = vp; /* cast required in C++, not in C */
    }
 
 
 
    return 0;
}
 
/* matches declaration in C, not in C++ */
void f(int i) { }

prog.cpp:13:13: error: conflicting declaration ‘typedef int S’
 typedef int S;
             ^
prog.cpp:12:8: error: ‘struct S’ has a previous declaration as ‘struct S’
 struct S { int i; };
        ^
prog.cpp:18:14: error: aggregate ‘Inner inner’ has incomplete type and cannot be defined
 struct Inner inner;
              ^
prog.cpp:22:3: error: ISO C++ forbids declaration of ‘g’ with no type [-fpermissive]
 g() {
   ^
prog.cpp:30:5: error: redefinition of ‘int n’
 int n;
     ^
prog.cpp:29:5: error: ‘int n’ previously declared here
 int n;
     ^
prog.cpp:34:9: error: variable or field ‘h’ declared void
 void h(i) int i; { }
         ^
prog.cpp:34:8: error: ‘i’ was not declared in this scope
 void h(i) int i; { }
        ^
prog.cpp:34:18: error: expected unqualified-id before ‘{’ token
 void h(i) int i; { }
                  ^
prog.cpp:38:1: error: new types may not be defined in a return type
 struct S2{int a;} j(void) { struct S2 s = {1}; return s; }
 ^
prog.cpp:38:1: note: (perhaps a semicolon is missing after the definition of ‘S2’)
prog.cpp:47:12: error: invalid conversion from ‘int’ to ‘E’ [-fpermissive]
 enum E e = 1;
            ^
prog.cpp: In function ‘void k()’:
prog.cpp:54:1: error: jump to label ‘label’ [-fpermissive]
 label:
 ^
prog.cpp:51:10: error:   from here [-fpermissive]
     goto label; /* C allows jumping past an initialization */
          ^
prog.cpp:53:13: error:   crosses initialization of ‘int x’
         int x = 0;
             ^
prog.cpp: In function ‘int main()’:
prog.cpp:66:8: error: too many arguments to function ‘void f()’
     f(1); /* doesn't match declaration in C++ */
        ^
prog.cpp:63:6: note: declared here
 void f();
      ^
prog.cpp:69:13: error: expected unqualified-id before ‘new’
         int new = 0;
             ^
prog.cpp:75:24: error: ‘puts’ was not declared in this scope
     puts("C is not C++");
                        ^
prog.cpp:80:12: error: invalid conversion from ‘void*’ to ‘int*’ [-fpermissive]
         ip = vp; /* cast required in C++, not in C */
            ^

Standard output is empty