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In C/C++ bitwise shifting a value by a number of bits which is either a negative number or is greater than or equal to the total number of bits in this value results in undefined behavior. The safest way (regardless of compiler vendor) is to always keep the number of bits to shift (the right operand of the << and >> bitwise operators ) within ...
stdarg.h is a header in the C standard library of the C programming language that allows functions to accept an indefinite number of arguments. [1] It provides facilities for stepping through a list of function arguments of unknown number and type.
The C standard does not say that the null pointer is the same as the pointer to memory address 0, though that may be the case in practice. Dereferencing a null pointer is undefined behavior in C, [7] and a conforming implementation is allowed to assume that any pointer that is dereferenced is not null.
Forward declaration is used in languages that require declaration before use; it is necessary for mutual recursion in such languages, as it is impossible to define such functions (or data structures) without a forward reference in one definition: one of the functions (respectively, data structures) must be defined first. It is also useful to ...
A smart pointer typically uses reference counting to reclaim objects. Some other techniques include the tombstones method and the locks-and-keys method. [3] Another approach is to use the Boehm garbage collector, a conservative garbage collector that replaces standard memory allocation functions in C and C++ with a garbage collector. This ...
An undefined variable in the source code of a computer program is a variable that is accessed in the code but has not been declared by that code. [1] In some programming languages, an implicit declaration is provided the first time such a variable is encountered at compile time. In other languages such a usage is considered to be sufficiently ...
The GNU Compiler Collection and the Solaris Studio C compiler share the same syntax for annotating symbols as weak, namely a special #pragma, #pragma weak, and, alternatively, a function and variable attribute, __attribute__((weak)).
However, GCC's nested functions, unlike blocks, must not be called after the containing scope has exited, as that would result in undefined behavior. GCC-style nested functions currently use dynamic creation of executable thunks on most architectures when taking the address of the nested function. On most architectures (including X86), these ...