On Thursday, 18 August 2022 at 08:41:02 UTC, LinguisticMystic
wrote:
I'm porting some C code for arena allocator to D, and somehow
the flexible array members (a feature of C99 for
dynamically-sized structs) work in D without significant
changes in the code. Here's my arena definition:
```
struct ArenaChunk {
size_t size;
ArenaChunk* next;
char[] memory; // flexible array member
}
struct Arena {
ArenaChunk* firstChunk;
ArenaChunk* currChunk;
int currInd;
}
```
And here's how I use the FAM's memory for allocating stuff:
```
void* result = cast(void*)(&ar.currChunk.memory +
ar.currInd);
```
I think the closest way to approximate this in D is to use a
zero-length static array:
```d
struct ArenaChunk {
size_t size;
ArenaChunk* next;
char[0] memory;
}
```
Then your usage example becomes
```
void* result = cast(void*)(ar.currChunk.memory.ptr +
ar.currInd);
```
Note that in D you must use `.ptr` to get a pointer to the
array's first element; it does not decay automatically like in C.
