Search results
Results From The WOW.Com Content Network
Fix templates are typically predefined changes for fixing specific classes of bugs. [15] Examples of fix templates include inserting a conditional statement to check whether the value of a variable is null to fix null pointer exception, or changing an integer constant by one to fix off-by-one errors. [15]
To expose dangling pointer errors, one common programming technique is to set pointers to the null pointer or to an invalid address once the storage they point to has been released. When the null pointer is dereferenced (in most languages) the program will immediately terminate—there is no potential for data corruption or unpredictable behavior.
Null pointer dereference – A null pointer dereference will often cause an exception or program termination in most environments, but can cause corruption in operating system kernels or systems without memory protection or when use of the null pointer involves a large or negative offset.
Depending on the operating system, the CPU can automatically detect such an invalid access (e.g. for the null value: a null pointer dereference error). This supports in analyzing the actual reason, a programming error, in debugging , and it can also be used to abort the program in production use, to prevent it from continuing with invalid data ...
Dereferencing a null pointer and then assigning to it (writing a value to a non-existent target) also usually causes a segmentation fault: int * ptr = NULL ; * ptr = 1 ; The following code includes a null pointer dereference, but when compiled will often not result in a segmentation fault, as the value is unused and thus the dereference will ...
In some programming language environments (at least one proprietary Lisp implementation, for example), [citation needed] the value used as the null pointer (called nil in Lisp) may actually be a pointer to a block of internal data useful to the implementation (but not explicitly reachable from user programs), thus allowing the same register to be used as a useful constant and a quick way of ...
The language does not provide any explicit pointer manipulation operators. It is still possible for code to attempt to dereference a null reference (null pointer), however, which results in a run-time exception being thrown. The space occupied by unreferenced memory objects is recovered automatically by garbage collection at run-time. [20]
If the types are not compatible, an exception will be thrown (when dealing with references) or a null pointer will be returned (when dealing with pointers). A Java typecast behaves similarly; if the object being cast is not actually an instance of the target type, and cannot be converted to one by a language-defined method, an instance of java ...