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[18] [19] The following example will cause undefined behavior in both C and C++. int f ( int i ) { return i ++ + i ++ ; /* undefined behavior: two unsequenced modifications to i */ } When modifying an object between two sequence points, reading the value of the object for any other purpose than determining the value to be stored is also ...
The final value of k is undefined. The answer that it must be 10 assumes that it started at zero, which may or may not be true. Note that in the example, the variable i is initialized to zero by the first clause of the for statement. Another example can be when dealing with structs.
This can be understood as taking a null pointer of type structure st, and then obtaining the address of member m within said structure. While this implementation works correctly in many compilers, it has generated some debate regarding whether this is undefined behavior according to the C standard, [2] since it appears to involve a dereference of a null pointer (although, according to the ...
The detailed semantics of "the" ternary operator as well as its syntax differs significantly from language to language. A top level distinction from one language to another is whether the expressions permit side effects (as in most procedural languages) and whether the language provides short-circuit evaluation semantics, whereby only the selected expression is evaluated (most standard ...
The BIT data type, which can only store integers 0 and 1 apart from NULL, is commonly used as a workaround to store Boolean values, but workarounds need to be used such as UPDATE t SET flag = IIF (col IS NOT NULL, 1, 0) WHERE flag = 0 to convert between the integer and Boolean expression.
The constants 1 and 0 are sometimes used to represent the Boolean values true and false in programming languages without a Boolean type, such as older versions of C. Most modern programming languages provide a boolean or bool primitive type and so the use of 0 and 1 is ill-advised. This can be more confusing since 0 sometimes means programmatic ...
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 ...
An undefined value must not be confused with empty string, Boolean "false" or other "empty" (but defined) values. Depending on circumstances, evaluation to an undefined value may lead to exception or undefined behaviour, but in some programming languages undefined values can occur during a normal, predictable course of program execution.