Language in C 面试题与答案
Question: What does the error "Null Pointer Assignment" mean and what causes this error?
Answer: The Null Pointer Assignment error is generated only in small and medium memory models. This error occurs in programs which attempt to change the bottom of the data segment. In Borland's C or C++ compilers, Borland places four zero bytes at the bottom of the data segment, followed by the Borland copyright notice "Borland C++ - Copyright 1991 Borland Intl.". In the small and medium memory models, a null pointer points to DS:0000. Thus assigning a value to the memory referenced by this pointer will overwrite the first zero byte in the data segment. At program termination, the four zeros and the copyright banner are checked. If either has been modified, then the Null Pointer Assignment error is generated. Note that the pointer may not truly be null, but may be a wild pointer that references these key areas in the data segment.Data Structures |
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