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We could use these 4 bits to mark the table entry with extra information. For example, bit 0 might mean read only, bit 1 might mean dirty (the table entry needs to be updated), and so on. If pointers are 16-bit values, then: 0x3421 is a read-only pointer to the table_entry at address 0x3420; 0xf472 is a pointer to a dirty table_entry at address ...
Whereas the former example relied only on guarantees made by the C programming language about structure layout and pointer convertibility, the latter example relies on assumptions about a particular system's hardware. Some situations, such as time-critical code that the compiler otherwise fails to optimize, may require
As such, the compiler must also generate "hidden" code in the constructors of each class to initialize a new object's virtual table pointer to the address of its class's virtual method table. Many compilers place the virtual table pointer as the last member of the object; other compilers place it as the first; portable source code works either ...
There are no practical limits to the precision except the ones implied by the available memory (operands may be of up to 2 32 −1 bits on 32-bit machines and 2 37 bits on 64-bit machines). [ 4 ] [ 5 ] GMP has a rich set of functions, and the functions have a regular interface.
A basic example is in the argv argument to the main function in C (and C++), which is given in the prototype as char **argv—this is because the variable argv itself is a pointer to an array of strings (an array of arrays), so *argv is a pointer to the 0th string (by convention the name of the program), and **argv is the 0th character of the ...
For this purpose, the C++11 standard library defines the smart pointer classes std::unique_ptr for single-owned objects and std::shared_ptr for objects with shared ownership. Similar classes are also available through std::auto_ptr in C++98, and boost::shared_ptr in the Boost libraries. Also, messages can be sent to network resources using RAII.
The lazy initialization technique allows us to do this in just O(m) operations, rather than spending O(m+n) operations to first initialize all array cells. The technique is simply to allocate a table V storing the pairs ( k i , v i ) in some arbitrary order, and to write for each i in the cell T [ k i ] the position in V where key k i is stored ...
In 1989, C++ 2.0 was released, followed by the updated second edition of The C++ Programming Language in 1991. [32] New features in 2.0 included multiple inheritance, abstract classes, static member functions, const member functions, and protected members. In 1990, The Annotated C++ Reference Manual was published. This work became the basis for ...