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Memory corruption occurs in a computer program when the contents of a memory location are modified due to programmatic behavior that exceeds the intention of the original programmer or program/language constructs; this is termed as violation of memory safety. The most likely causes of memory corruption are programming errors (software bugs ...
Uninitialized variables are a particular problem in languages such as assembly language, C, and C++, which were designed for systems programming. The development of these languages involved a design philosophy in which conflicts between performance and safety were generally resolved in favor of performance.
This most often occurs due to jumping over the initialization, not by omitting it. Most compilers are able to warn about this. int f ( int i ) { char * dp ; /* dp is a wild pointer */ static char * scp ; /* scp is not a wild pointer: * static variables are initialized to 0 * at start and retain their values from * the last call afterwards.
In C++, because dereferencing a null pointer is undefined behavior, compiler optimizations may cause other checks to be removed, leading to vulnerabilities elsewhere in the code. [ 29 ] [ 30 ] Some lists may also include race conditions (concurrent reads/writes to shared memory) as being part of memory safety (e.g., for access control).
Dereferencing any of these variables could cause a segmentation fault: dereferencing the null pointer generally will cause a segfault, while reading from the wild pointer may instead result in random data but no segfault, and reading from the dangling pointer may result in valid data for a while, and then random data as it is overwritten.
Used by Microsoft's C++ debugging runtime library and many DOS environments to mark uninitialized stack memory. CC is the opcode of the INT 3 debug breakpoint interrupt on x86 processors. [30] CDCDCDCD: Used by Microsoft's C/C++ debug malloc() function to mark uninitialized heap memory, usually returned from HeapAlloc() [26] 0D15EA5E
C++26 is the informal name for the version of the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) 14882 standard for the C++ programming language that follows C++23. The current working draft of this version is N4981.
This shows the typical layout of a simple computer's program memory with the text, various data, and stack and heap sections. Historically, BSS (from Block Started by Symbol) is a pseudo-operation in UA-SAP (United Aircraft Symbolic Assembly Program), the assembler developed in the mid-1950s for the IBM 704 by Roy Nutt, Walter Ramshaw, and others at United Aircraft Corporation.