Made Capstone an optional dependency (fixes #382) (#383)

* Made Capstone an optional dependency (fixes #382).

* Introduced feature 'disas' for disassembly (related to #382).

* Made 'disas' a default feature in cretonne-tools.

* Fixed errors in src/compile.rs introduced by get_disassembler changes.

- Moves `use` statements before the function declaration.
- Returns an error if the disassembler cannot be found created.

cranelift/Cargo.toml

@@ -29,12 +29,13 @@ docopt = "1"
 serde = "1.0.8"
 serde_derive = "1.0.8"
 term = "0.5.1"
-capstone = "0.4"
+capstone = { version = "0.4", optional = true }
 wabt = { version = "0.3", optional = true }
 target-lexicon = "0.0.2"
 
 [features]
-default = ["wasm"]
+default = ["disas", "wasm"]
+disas = ["capstone"]
 wasm = ["wabt", "cretonne-wasm"]
 
 [workspace]

cranelift/src/compile.rs

@@ -1,6 +1,5 @@
 //! CLI tool to read Cretonne IR files and compile them into native code.
 
-use capstone::prelude::*;
 use cretonne_codegen::isa::TargetIsa;
 use cretonne_codegen::print_errors::pretty_error;
 use cretonne_codegen::settings::FlagsOrIsa;
@@ -9,7 +8,6 @@ use cretonne_codegen::{binemit, ir};
 use cretonne_reader::parse_test;
 use std::path::Path;
 use std::path::PathBuf;
-use target_lexicon::Architecture;
 use utils::{parse_sets_and_triple, read_to_string};
 
 struct PrintRelocs {
@@ -121,22 +119,21 @@ fn handle_module(
                 }
                 print!("{}", byte);
             }
+
             println!();
-
-            let mut cs = get_disassembler(isa)?;
-
-            println!("\nDisassembly:");
-            let insns = cs.disasm_all(&mem, 0x0).unwrap();
-            for i in insns.iter() {
-                println!("{}", i);
-            }
+            print_disassembly(isa, &mem)?;
         }
     }
 
     Ok(())
 }
 
-fn get_disassembler(isa: &TargetIsa) -> Result<Capstone, String> {
+cfg_if! {
+    if #[cfg(feature = "disas")] {
+        use capstone::prelude::*;
+        use target_lexicon::Architecture;
+
+        fn get_disassembler(isa: &TargetIsa) -> Result<Capstone, String> {
             let cs = match isa.triple().architecture {
                 Architecture::Riscv32 | Architecture::Riscv64 => {
                     return Err(String::from("No disassembler for RiscV"))
@@ -166,4 +163,22 @@ fn get_disassembler(isa: &TargetIsa) -> Result<Capstone, String> {
             };
 
             cs.map_err(|err| err.to_string())
+        }
+
+        fn print_disassembly(isa: &TargetIsa, mem: &[u8]) -> Result<(), String> {
+            let mut cs = get_disassembler(isa)?;
+
+            println!("\nDisassembly:");
+            let insns = cs.disasm_all(&mem, 0x0).unwrap();
+            for i in insns.iter() {
+                println!("{}", i);
+            }
+            Ok(())
+        }
+    } else {
+        fn print_disassembly(_: &TargetIsa, _: &[u8]) -> Result<(), String> {
+            println!("\nNo disassembly available.");
+            Ok(())
+        }
+    }
 }

cranelift/src/cton-util.rs

@@ -17,6 +17,7 @@ extern crate docopt;
 extern crate filecheck;
 #[macro_use]
 extern crate serde_derive;
+#[cfg(feature = "disas")]
 extern crate capstone;
 extern crate term;