Rollup merge of rust-lang#39193 - pepyakin:emcc-strip-panic-rt, r=ale…

…xcrichton

Tell emscripten to remove exception handling code when panic=abort

Fixes rust-lang#36900

src/librustc_back/target/asmjs_unknown_emscripten.rs

@@ -22,6 +22,7 @@ pub fn target() -> Result<Target, String> {
         linker_is_gnu: true,
         allow_asm: false,
         obj_is_bitcode: true,
+        is_like_emscripten: true,
         max_atomic_width: Some(32),
         post_link_args: vec!["-s".to_string(), "ERROR_ON_UNDEFINED_SYMBOLS=1".to_string()],
         target_family: Some("unix".to_string()),

src/librustc_back/target/mod.rs

@@ -330,6 +330,10 @@ pub struct TargetOptions {
     /// Whether the target toolchain is like Android's. Only useful for compiling against Android.
     /// Defaults to false.
     pub is_like_android: bool,
+    /// Whether the target toolchain is like Emscripten's. Only useful for compiling with
+    /// Emscripten toolchain.
+    /// Defaults to false.
+    pub is_like_emscripten: bool,
     /// Whether the linker support GNU-like arguments such as -O. Defaults to false.
     pub linker_is_gnu: bool,
     /// The MinGW toolchain has a known issue that prevents it from correctly
@@ -428,6 +432,7 @@ impl Default for TargetOptions {
             is_like_solaris: false,
             is_like_windows: false,
             is_like_android: false,
+            is_like_emscripten: false,
             is_like_msvc: false,
             linker_is_gnu: false,
             allows_weak_linkage: true,
@@ -603,6 +608,7 @@ impl Target {
         key!(is_like_solaris, bool);
         key!(is_like_windows, bool);
         key!(is_like_msvc, bool);
+        key!(is_like_emscripten, bool);
         key!(is_like_android, bool);
         key!(linker_is_gnu, bool);
         key!(allows_weak_linkage, bool);
@@ -767,6 +773,7 @@ impl ToJson for Target {
         target_option_val!(is_like_solaris);
         target_option_val!(is_like_windows);
         target_option_val!(is_like_msvc);
+        target_option_val!(is_like_emscripten);
         target_option_val!(is_like_android);
         target_option_val!(linker_is_gnu);
         target_option_val!(allows_weak_linkage);

src/librustc_back/target/wasm32_unknown_emscripten.rs

@@ -24,6 +24,7 @@ pub fn target() -> Result<Target, String> {
         linker_is_gnu: true,
         allow_asm: false,
         obj_is_bitcode: true,
+        is_like_emscripten: true,
         max_atomic_width: Some(32),
         post_link_args: vec!["-s".to_string(), "BINARYEN=1".to_string(),
                              "-s".to_string(), "ERROR_ON_UNDEFINED_SYMBOLS=1".to_string()],

src/librustc_trans/back/link.rs

@@ -29,6 +29,7 @@ use rustc::dep_graph::DepNode;
 use rustc::hir::def_id::CrateNum;
 use rustc::hir::svh::Svh;
 use rustc_back::tempdir::TempDir;
+use rustc_back::PanicStrategy;
 use rustc_incremental::IncrementalHashesMap;
 
 use std::ascii;
@@ -714,6 +715,11 @@ fn link_natively(sess: &Session,
         cmd.arg(root.join(obj));
     }
 
+    if sess.target.target.options.is_like_emscripten &&
+       sess.panic_strategy() == PanicStrategy::Abort {
+        cmd.args(&["-s", "DISABLE_EXCEPTION_CATCHING=1"]);
+    }
+
     {
         let mut linker = trans.linker_info.to_linker(&mut cmd, &sess);
         link_args(&mut *linker, sess, crate_type, tmpdir,