Search results
Results From The WOW.Com Content Network
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 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.
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.
Here is an example of ANSI C code that will generally cause a segmentation fault on platforms with memory protection. It attempts to modify a string literal, which is undefined behavior according to the ANSI C standard. Most compilers will not catch this at compile time, and instead compile this to executable code that will crash:
Dangling pointers arise during object destruction, when an object that has an incoming reference is deleted or deallocated, without modifying the value of the pointer, so that the pointer still points to the memory location of the deallocated memory.
A segment value of 3 would mean the offset to the data of the fourth segment load command in the Mach-O file starting from zero up (0,1,2,3 = 4th segment). Sections are also numbered from sections 1 and up. Section value zero is used in the symbol table for symbols that are not defined in any section (undefined).
In the child process, the return value appears as zero (which is an invalid process identifier). The child process prints the desired greeting message, then exits. (For technical reasons, the POSIX _exit function must be used here instead of the C standard exit function.)
The value of x cannot be negative and, given that signed integer overflow is undefined behavior in C, the compiler can assume that value < 2147483600 will always be false. Thus the if statement, including the call to the function bar , can be ignored by the compiler since the test expression in the if has no side effects and its condition will ...