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What is the difference between undefined and unspecified?
Undefined behavior is simply behavior that is not defined by the C++ specification. In case of unspecified behavior, the C++ standard provides multiple possible paths doesn’t require the implementation to document or guarantee anything.
What is implementation dependent?
Implementation dependent means that a certain construct differs from platform to platform but in a defined, well-specified manner. ( e.g. the va_arg family of macros in C varies between posix and windows) Undefined behaviour means that anything (literally) could happen.
Does C++ have undefined behavior?
C and C++ have undefined behaviors because it allows compilers to avoid lots of checks. It also helps in wrap-around then compile-time checks which would not be possible without the greater knowledge of the undefined behavior in the C/C++ compiler.
Which is an example of an undefined behavior?
undefined behavior – there are no restrictions on the behavior of the program. Examples of undefined behavior are memory accesses outside of array bounds, signed integer overflow, null pointer dereference, modification of the same scalar more than once in an expression without sequence points, access to an object through a pointer…
When does division by zero result in undefined behavior?
Integer division by zero results in undefined behavior: Certain pointer operations may result in undefined behavior: In C and C++, the comparison of pointers to objects is only strictly defined if the pointers point to members of the same object, or elements of the same array.
When does undefined behavior lead to security vulnerabilities?
In scenarios where security is critical, undefined behavior can lead to security vulnerabilities in software. When GCC ‘s developers changed their compiler in 2008 such that it omitted certain overflow checks that relied on undefined behavior, CERT issued a warning against the newer versions of the compiler.
When to use shall, shall not, undefined behavior?
The text of the standard uses shall, shall not, and ill-formed to indicate these requirements. ill-formed, no diagnostic required – the program has semantic errors which may not be diagnosable in general case (e.g. violations of the ODR or other errors that are only detectable at link time). The behavior is undefined if such program is executed.