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sizeof is a unary operator in the programming languages C and C++. It generates the storage size of an expression or a data type , measured in the number of char -sized units. Consequently, the construct sizeof (char) is guaranteed to be 1 .
The std::string class is the standard representation for a text string since C++98. The class provides some typical string operations like comparison, concatenation, find and replace, and a function for obtaining substrings. An std::string can be constructed from a C-style string, and a C-style string can also be obtained from one. [7]
The operator sizeof yields a value of the type size_t. The maximum size of size_t is provided via SIZE_MAX, a macro constant which is defined in the <stdint.h> header (cstdint header in C++). size_t is guaranteed to be at least 16 bits wide. Additionally, POSIX includes ssize_t, which is a signed integer type of the same width as size_t.
All logical operators exist in C and C++ and can be overloaded in C++, albeit the overloading of the logical AND and logical OR is discouraged, because as overloaded operators they behave as ordinary function calls, which means that both of their operands are evaluated, so they lose their well-used and expected short-circuit evaluation property ...
This was recognized as a defect in the standard and fixed in C++.) [4] C++11 and C11 add two types with explicit widths char16_t and char32_t. [5] Variable-width encodings can be used in both byte strings and wide strings. String length and offsets are measured in bytes or wchar_t, not in "characters", which can be confusing to beginning ...
The sizeof operator on such a struct gives the size of the structure as if the flexible array member were empty. This may include padding added to accommodate the flexible member; the compiler is also free to re-use such padding as part of the array itself.
A long double (eight bytes with Visual C++, sixteen bytes with GCC) will be 8-byte aligned with Visual C++ and 16-byte aligned with GCC. Any pointer (eight bytes) will be 8-byte aligned. Some data types are dependent on the implementation. Here is a structure with members of various types, totaling 8 bytes before compilation:
The C and C++ syntax given above is the canonical one used in all the textbooks - but it's difficult to read and explain. Even the above typedef examples use this syntax. However, every C and C++ compiler supports a more clear and concise mechanism to declare function pointers: use typedef , but don't store the pointer as part of the definition.