On: Linear Address Spaces: Unsafe at any speed

[gpderetta]

Yes, notoriously you can't implement malloc in portable C.

In C++, I think they added enough magic in that you should now be able to do it (placement new, std::launder and numerous other hacks).

[rkangel → gpderetta]

I've implemented a pools allocator for embedded devices a couple of times. Allocating memory for callers out of a block of static memory. I thought it was portable C. Which detail of the standard did I not realise I was running into?

[gpderetta → rkangel]

I assume the block of static memory was a large static char array.

My understanding that reusing the storage would violate the aliasing rules[1] and the rules against overlapping object lifetimes.

[1] while char ptrs can be used to access everything, the reverse is not allowed.

[teddyh → gpderetta]

Reportedly you can implement malloc in C, using mmap().

[gpderetta → teddyh]

well mmap is posix, not standard portable C.