Кто изобрел бросок/попытку/выгоду [/наконец] вид обработки ошибок?
Моими вопросами является больше исторической природы, чем практичный:
- Кто изобрел его?
- Какой язык использовал его сначала (и до какой степени)?
- Какова была исходная идея, базовое понятие (какие фактические проблемы должны были быть решены в эти дни, приветствующиеся бумаги)?
- Действительно ли система условия LISP является предком текущей обработки исключений?
3 ответа
Today's Common Lisp condition system is a relative newcomer. The design was based on previous systems, but wasn't included as part of the Common Lisp language until the late 80's around the time of CLTL2
I believe the conditions chapter in that book has a fair amount commentary on the history and background of the design, and references to related research and prior implementations of similar systems.
The VAX CPUs had a stack-based exception handling system. In every call frame, one 32-bit cell was allocated and filled with a zero. If the subroutine being called wanted to handle exceptions, all it had to do was fill in that cell with the address of the exception-handling routine.
When an exception took place, a stack search would occur. This was easy, since the stack frames were all chained together. The first stack frame with a non-zero entry would cause an stack unwind to that point, and the exception handler would be called.
I remember this as being one of the features of the processor which were aimed at higher-level languages, but I don't know that there was a higher-level language that took advantage of the feature. I believe it was used by library code, which would likely have been written in assembler.
Doesn't it go back to the setjmp, longjmp functions in C? Richie, Kernighan, et al?