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Language Extensions
Example 3-2 Linkage specification
extern const int z; /* in read-only segment, cannot */
/* be dynamically initialized */
extern "C++:read/write" const int y; /* in read/write segment */
/* can be dynamically initialized */
extern "C++:read/write"
{
const int i=5; /* placed in read-only segment, */
/* not extern because implicitly static */
extern const T x=6; /* placed in read/write segment */
struct S
{
static const T T x; /* placed in read/write segment */
};
}
Constant objects must not be redeclared with another linkage. The code in Example 3-3
produces a compile error.
Example 3-3 Compiler error
extern "C++" const T x;
extern "C++:read/write" const T x; /* error */
Note
Because C does not have the linkage specifications, you cannot use a const object
declared in C++ as extern "C++:read/write" from C.
See also
• --apcs=qualifer...qualifier on page 2-4.
3.5.5 Scalar type constants
Constants of scalar type can be defined within classes. This is an old form. The modern
form uses an initialized static data member.
Errors
A warning is issued if you define a member of constant integral type within a class.
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