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Differences between C and C++ linkage and calling conventions can also have subtle implications for code that uses function pointers. Some compilers will produce non-working code if a function pointer declared extern "C" points to a C++ function that is not declared extern "C". [22] For example, the following code:
Additionally, most standard library procedures provide v-prefixed alternative versions which accept a reference to the unnamed argument list (i.e. an initialized va_list variable) instead of the unnamed argument list itself. For example, vfprintf() is an alternate version of fprintf() expecting a va_list instead of the actual unnamed argument list.
Download as PDF; Printable version; In other projects ... unfortunately the only fix in this situation is to not use list-defined references for entries that ...
In the C++ programming language, a reference is a simple reference datatype that is less powerful but safer than the pointer type inherited from C.The name C++ reference may cause confusion, as in computer science a reference is a general concept datatype, with pointers and C++ references being specific reference datatype implementations.
In some programming language environments (at least one proprietary Lisp implementation, for example), [citation needed] the value used as the null pointer (called nil in Lisp) may actually be a pointer to a block of internal data useful to the implementation (but not explicitly reachable from user programs), thus allowing the same register to be used as a useful constant and a quick way of ...
But a reference (pointer) to it can be passed to another function, allowing it to read and modify the contents of the variable (again without referring to it by name). External variables are allocated and initialized when the program starts, and the memory is only released when the program ends. Their lifetime is the same as the program's.
This is also valid in C++. (C++ 98/03 deprecated this usage in favor of anonymous namespaces, but is no longer deprecated in C++ 11.) Also, C++ implicitly treats any const namespace-scope variable as having internal linkage unless it is explicitly declared extern, unlike C. A name's linkage is related to, but distinct from, its scope. The scope ...
In the C and C++ languages, such non-portable constructs are generally grouped into three categories: Implementation-defined, unspecified, and undefined behavior. [3] The exact definition of unspecified behavior varies. In C++, it is defined as "behavior, for a well-formed program construct and correct data, that depends on the implementation."