On Saturday, 14 October 2017 at 09:32:32 UTC, Timon Gehr wrote:
Also, UB can and does sometimes mean that the program can execute arbitrary code. It's called "arbitrary code execution": https://en.wikipedia.org/wiki/Arbitrary_code_execution
This confuses different levels of reasoning. In C/C++ "undefined behavior" is a property of the SOURCE code with respect to the specification. It states: The spec does not not apply, it does not define the semantic.
This issue is totally different from the question what a given program containing undefined behavior actually does after is compiles and the after the linker produces an executable. This is reasoning about generated MACHINE code.
A result of this confusion has been that some clever people tried to "detect" certain kinds of undefined behavior "after" they "happended". E.g. <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=30475> This is the danger of undefined behavior: The MACHINE code may also work as the programmer expected. At least for some time.
