Maintain compatibility with Rust 1.25

.travis.yml

@@ -43,6 +43,10 @@ matrix:
     - rust: nightly
       script: *test_all
 
+    # Make sure the default crate builds with 1.25.0
+    - rust: 1.25.0
+      script: cargo test
+
     # Upload docs on nightly
     - rust: nightly
       script:

Cargo.toml

@@ -41,6 +41,9 @@ winapi = { version = "0.3.3", features = ["dbghelp", "processthreadsapi", "winnt
 [target.'cfg(all(unix, not(target_os = "fuchsia"), not(target_os = "emscripten"), not(target_os = "macos"), not(target_os = "ios")))'.dependencies]
 backtrace-sys = { path = "backtrace-sys", version = "0.1.17", optional = true }
 
+[build-dependencies]
+autocfg = "0.1"
+
 # Each feature controls the two phases of finding a backtrace: getting a
 # backtrace and then resolving instruction pointers to symbols. The default
 # feature enables all the necessary features for each platform this library

build.rs

@@ -0,0 +1,13 @@
+extern crate autocfg;
+
+fn main() {
+    let ac = autocfg::new();
+
+    // ffi types moved from `std` to `core` in Rust 1.30, so we need to adjust imports based on
+    // this.
+    //
+    // <https://github.com/rust-lang/rust/pull/53910>
+    ac.emit_rustc_version(1, 30);
+
+    println!("cargo:rerun-if-changed=build.rs");
+}

src/symbolize/dbghelp.rs

@@ -10,9 +10,18 @@
 
 #![allow(bad_style)]
 
+// This is a hack for compatibility with rustc 1.25.0. The no_std mode of this
+// crate is not supported pre-1.30.0, but in std mode the `char` module here
+// moved in rustc 1.26.0 (ish). As a result, in std mode we use `std::char` to
+// retain compatibility with rustc 1.25.0, but in `no_std` mode (which is
+// 1.30.0+ already) we use `core::char`.
+#[cfg(feature = "std")]
+use std::char;
+#[cfg(not(feature = "std"))]
+use core::char;
+
 use core::mem;
 use core::slice;
-use core::char;
 
 use winapi::ctypes::*;
 use winapi::shared::basetsd::*;

src/types.rs

@@ -7,8 +7,10 @@ cfg_if! {
         use std::fmt;
         use std::path::PathBuf;
         use std::prelude::v1::*;
-    } else {
+    } else if #[cfg(rustc_1_30)] {
         pub use core::ffi::c_void;
+    } else {
+        compile_error!("`backtrace` requires Rust >=1.30.0 to support `no_std`.");
     }
 }
 
@@ -31,8 +33,8 @@ impl<'a> BytesOrWideString<'a> {
         use self::BytesOrWideString::*;
 
         match self {
-            Bytes(slice) => String::from_utf8_lossy(slice),
-            Wide(wide) => Cow::Owned(String::from_utf16_lossy(wide)),
+            &Bytes(slice) => String::from_utf8_lossy(slice),
+            &Wide(wide) => Cow::Owned(String::from_utf16_lossy(wide)),
         }
     }