Add to_string and to_string_alt, along with alloc and std features

Fixes rust-lang#20

.github/workflows/main.yml

@@ -14,6 +14,27 @@ jobs:
       run: rustup update ${{ matrix.rust }} && rustup default ${{ matrix.rust }}
     - run: cargo build --all
     - run: cargo test --all
+    - run: cargo build --all --features=alloc
+    - run: cargo test --all --features=alloc
+    - run: cargo build --all --features=std
+    - run: cargo test --all --features=std
+    - run: cargo build --all --features=alloc,std
+    - run: cargo test --all --features=alloc,std
+
+  test-old:
+    name: Test on old releases of Rust
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust: [1.31.1]
+    steps:
+    - uses: actions/checkout@master
+    - name: Install Rust
+      run: rustup update ${{ matrix.rust }} && rustup default ${{ matrix.rust }}
+    - run: cargo build --all
+    - run: cargo test --all
+    - run: cargo build --all --features=std
+    - run: cargo test --all --features=std
 
   rustfmt:
     name: Rustfmt
@@ -32,7 +53,7 @@ jobs:
       - name: Install Rust
         run: rustup update stable && rustup default stable
       - name: Build documentation
-        run: cargo doc --no-deps
+        run: cargo doc --no-deps --features alloc
       - name: Publish documentation
         run: |
           cd target/doc

Cargo.toml

@@ -20,6 +20,14 @@ compiler_builtins = { version = '0.1.2', optional = true }
 
 [features]
 rustc-dep-of-std = ['core', 'compiler_builtins']
+alloc = []
+std = []
 
 [profile.release]
 lto = true
+
+[package.metadata.docs.rs]
+features = ["alloc"]
+
+[package.metadata.playground]
+features = ["alloc"]

README.md

@@ -10,12 +10,24 @@ You can add this as a dependency via your `Cargo.toml`
 
 ```toml
 [dependencies]
-rustc-demangle = "0.1"
+rustc-demangle = { version = "0.1", features = ["alloc"] }
 ```
 
 and then be sure to check out the [crate
 documentation](https://docs.rs/rustc-demangle) for usage.
 
+### Features
+
+The `alloc` feature enables the functionality that requires a memory allocator
+(the [`alloc`] crate).
+
+The `std` feature enables the functionality that requires the [`std`] crate
+(currently doesn't enable any more than the `alloc` feature, but works on old
+versions of Rust from before the [`alloc`] crate was stabilized).
+
+[`alloc`]: https://doc.rust-lang.org/alloc/index.html
+[`std`]: https://doc.rust-lang.org/std/index.html
+
 ## Usage from non-Rust languages
 
 You can also use this crate from other languages via the C API wrapper in the

src/lib.rs

@@ -26,14 +26,22 @@
 #![no_std]
 #![deny(missing_docs)]
 
-#[cfg(test)]
+#[cfg(any(test, feature = "std"))]
 #[macro_use]
 extern crate std;
 
+#[cfg(all(feature = "alloc", not(feature = "std"), not(test)))]
+#[macro_use]
+extern crate alloc;
+
 mod legacy;
 mod v0;
 
+#[cfg(all(feature = "alloc", not(feature = "std"), not(test)))]
+use alloc::string::{String, ToString};
 use core::fmt;
+#[cfg(any(feature = "std", test))]
+use std::string::{String, ToString};
 
 /// Representation of a demangled symbol name.
 pub struct Demangle<'a> {
@@ -147,6 +155,20 @@ impl<'a> Demangle<'a> {
     pub fn as_str(&self) -> &'a str {
         self.original
     }
+    /// Returns the demangled symbol as a `String`.
+    ///
+    /// The same as `ToString::to_string(self)`
+    #[cfg(any(feature = "alloc", feature = "std", test))]
+    pub fn to_string(&self) -> String {
+        ToString::to_string(self)
+    }
+    /// Returns the demangled symbol as a `String`, in alternate format.
+    ///
+    /// The same as `format!("{:#}", self)`
+    #[cfg(any(feature = "alloc", feature = "std", test))]
+    pub fn to_string_alt(&self) -> String {
+        format!("{:#}", self)
+    }
 }
 
 fn is_symbol_like(s: &str) -> bool {
@@ -211,7 +233,7 @@ mod tests {
 
     macro_rules! t_nohash {
         ($a:expr, $b:expr) => {{
-            assert_eq!(format!("{:#}", super::demangle($a)), $b);
+            assert_eq!(super::demangle($a).to_string_alt(), $b);
         }};
     }