Use SmallRng instead of thread_rng which is not available on no_std

The RNG is seeded from the current time to yield different random values
on each invocation.

Signed-off-by: Daniel Egger <[email protected]>

Author: therealprof

macros/src/lib.rs

@@ -6,9 +6,13 @@ extern crate rand;
 extern crate quote;
 extern crate proc_macro2;
 extern crate syn;
+extern crate core;
 
+use core::mem;
 use proc_macro2::Span;
 use rand::Rng;
+use rand::SeedableRng;
+use std::time::{SystemTime, UNIX_EPOCH};
 use syn::{FnArg, Ident, Item, ItemFn, ItemStatic, ReturnType, Stmt, Type, Visibility};
 
 use proc_macro::TokenStream;
@@ -492,7 +496,9 @@ pub fn pre_init(args: TokenStream, input: TokenStream) -> TokenStream {
 
 // Creates a random identifier
 fn random_ident() -> Ident {
-    let mut rng = rand::thread_rng();
+    let seed = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs();
+    let seed = [seed, seed];
+    let mut rng = rand::rngs::SmallRng::from_seed( unsafe { mem::transmute(seed) } );
     Ident::new(
         &(0..16)
             .map(|i| {