Dummy atomic support (#92)

* Dummy atomic implementation
make some crates(like bytes, log) work on ckb-vm

Cargo.toml

@@ -24,6 +24,8 @@ dlopen-c = ["libc"]
 build-with-clang = []
 libc = []
 ckb2023 = []
+# work with `target-feature=-a` Cargo flag
+dummy-atomic = []
 
 [build-dependencies]
 cc = "1.0"

README.md

@@ -15,7 +15,7 @@ This library contains several modules that help you write CKB contract with Rust
 * `debug!` macro: a `println!` like macro helps debugging
 * `entry!` macro: defines contract entry point
 * `default_alloc!` macro: defines global allocator for no-std rust
-
+* `dummy_atomic` module: dummy atomic operations
 ### Memory allocator
 
 Default allocator uses a mixed allocation strategy:

build.rs

@@ -24,6 +24,10 @@ fn main() {
         setup_compiler_flags(&mut build);
         build.compile("libc");
     }
+    if target_arch != "riscv64" && cfg!(feature = "dummy-atomic") {
+        println!("cargo:warning=This build script intentionally failed: feature `dummy-atomic` can't be used in non risc-v target");
+        std::process::exit(1);
+    }
 }
 
 fn setup_compiler_flags(build: &mut cc::Build) {

contracts/ckb-std-tests/Cargo.toml

@@ -6,5 +6,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-ckb-std = { path = "../../", features = [ "dlopen-c" ] }
+ckb-std = { path = "../../", features = [ "dlopen-c", "dummy-atomic" ] }
 blake2b-ref = { version = "0.3", default-features = false }
+bytes = { version = "1.6.0", default-features = false }
+log = { version = "0.4.17", default-features = false }