+ adding compiler features for no_std environments other than wasm (i…

….e. SGX) (paritytech#2421)

core/sr-io/Cargo.toml

@@ -35,3 +35,5 @@ std = [
 nightly = []
 strict = []
 wasm-nice-panic-message = []
+no_panic_handler = []
+no_oom = []

core/sr-io/without_std.rs

@@ -22,6 +22,7 @@ use core::{intrinsics, panic::PanicInfo};
 use rstd::{vec::Vec, cell::Cell};
 use primitives::Blake2Hasher;
 
+#[cfg(not(feature = "no_panic_handler"))]
 #[panic_handler]
 #[no_mangle]
 pub fn panic(info: &PanicInfo) -> ! {
@@ -43,6 +44,7 @@ pub fn panic(info: &PanicInfo) -> ! {
 	}
 }
 
+#[cfg(not(feature = "no_oom"))]
 #[alloc_error_handler]
 pub extern fn oom(_: ::core::alloc::Layout) -> ! {
 	static OOM_MSG: &str = "Runtime memory exhausted. Aborting";

core/sr-std/Cargo.toml

@@ -13,3 +13,4 @@ default = ["std"]
 std = []
 nightly = []
 strict = []
+no_global_allocator = []

core/sr-std/without_std.rs

@@ -26,6 +26,7 @@ extern "C" {
 /// Wasm allocator
 pub struct WasmAllocator;
 
+#[cfg(not(feature = "no_global_allocator"))]
 #[global_allocator]
 static ALLOCATOR: WasmAllocator = WasmAllocator;