[fpc-pascal] Pointer to temporary string

[Jonas Maebe]

On 11 Mar 2012, at 15:46, cobines wrote:

> Is storing and using pointers to temporary strings safe?

No.

> Like in the
> following program. I think I remember reading on the mailing list that
> it is not, but I cannot find it. How can I prove one way or the other?

The only thing you can prove is finding code that crashes. You can't prove that it's safe, because it's impossible to prove a negative (namely that no code sequence exists that will crash).

> I could not get the program to crash, even if I used 20 variables, it
> didn't show any wrong result. Valgrind and Dr. Memory didn't show any
> problems.

Nevertheless it's not safe. It depends on management of temporary variables of the compiler, which in itself depends on the performed optimizations and compiler version. Just don't do it.


Jonas