3 ms·

trying to fetch from a memory address outside of your boundaries is a violation of a program's contract with the OS. It can't be "corrected" by the OS, and if y

trying to fetch from a memory address outside of your boundaries is a violation of a program's contract with the OS. It can't be "corrected" by the OS, and if you see the message, the program has not included a handler for it. If the program wishes to do something different, it can register a handler, and you won't see the message. If you see the message, there was a violation. If you don't see the message... well, there was still a violation, but it got handled.

klodolph 6y ago
The program has no such contract with the OS. The only contract is that if you access unmapped memory, you get a segmentation fault, and the relevant signal handler is invoked. The default signal handler terminates the program. Depending on the program, a segmentation fault may be routine. That’s why it doesn’t make sense to call it a violation.
- fsckboy 6y ago
  in systems with unprotected memory, you would actually access the address; even though you accessed it, it is a violation, the result is undefined. When there is protected memory, what catches the violation is outside of your process space. It is a violation; possibly I should not have said OS, it's a hardware violation. I'm not the only one who says this, look at the name, -V edit: actually, though hardware support is required for certain OS features, it's the OS that sets up the segmentation and the fault handlers so ... it is ultimately an OS contract.
  - klodolph 6y ago
    As the article notes, the -V suffix is a historical curiosity. Since no contract is being violated here, the term “violation” does not make sense. This is nothing more than a fault condition, like trying to open a file that does not exist or trying to go to a webpage that does not exist. The contract with the OS is that if you access unmapped memory, your program is sent SIGSEGV. Just like the contract with open() is that it returns -1 if the file is not found.

klodolph 6y ago

The program has no such contract with the OS. The only contract is that if you access unmapped memory, you get a segmentation fault, and the relevant signal handler is invoked. The default signal handler terminates the program. Depending on the program, a segmentation fault may be routine. That’s why it doesn’t make sense to call it a violation.

fsckboy 6y ago
in systems with unprotected memory, you would actually access the address; even though you accessed it, it is a violation, the result is undefined. When there is protected memory, what catches the violation is outside of your process space. It is a violation; possibly I should not have said OS, it's a hardware violation. I'm not the only one who says this, look at the name, -V edit: actually, though hardware support is required for certain OS features, it's the OS that sets up the segmentation and the fault handlers so ... it is ultimately an OS contract.
- klodolph 6y ago
  As the article notes, the -V suffix is a historical curiosity. Since no contract is being violated here, the term “violation” does not make sense. This is nothing more than a fault condition, like trying to open a file that does not exist or trying to go to a webpage that does not exist. The contract with the OS is that if you access unmapped memory, your program is sent SIGSEGV. Just like the contract with open() is that it returns -1 if the file is not found.