If a `HashMap` from `sgx_tstd` is created using `new` (or a `with_capacity`
with a low value) it can only be inserted to a few times, after which it will
segfault.
This is deeply concerning, and surprising (`HashMap` should survive this). As
an immediate consequence, for instance, the provided `tlsserver` example only
supports a few concurrent TLS sessions (because they are stored in a HashMap).
If it is created with `with_capacity`, some small values fail in the same
fashion, after which it seems to be OK. However the minimum value to make this
work seems to be contextual (!). This means that it may vary depending on the
surrounding code (!).
Here's an example:
```rust
#![crate_name = "hashmap"]
#![crate_type = "staticlib"]
#![cfg_attr(not(target_env = "sgx"), no_std)]
#![cfg_attr(target_env = "sgx", feature(rustc_private))]
#[cfg(not(target_env = "sgx"))]
#[macro_use]
extern crate sgx_tstd as std;
use std::collections::HashMap;
#[no_mangle]
pub extern "C"
fn e_do() {
let mut local_map = HashMap::with_capacity(2); // This could also be
HashMap::new()
for i in 0..1000 {
local_map.insert(i, 42);
eprintln!("l: inserted {}", i);
}
}
```
On my machine, if the initial capacity is 8, it seems fine (but in some
contexts, that capacity was lowered to 4, for some reason). It usually
segfaults in a few (<20) insertions, but this is probably machine-dependant.
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