Re-enable Emscripten's exception handling support

Passes LLVM codegen and Emscripten link-time flags for exception
handling if and only if the panic strategy is `unwind`. Sets the
default panic strategy for Emscripten targets to `unwind`. Re-enables
tests that depend on unwinding support for Emscripten, including
`should_panic` tests.

src/bootstrap/native.rs

@@ -534,6 +534,10 @@ impl Step for TestHelpers {
         builder.info("Building test helpers");
         t!(fs::create_dir_all(&dst));
         let mut cfg = cc::Build::new();
+        // FIXME: Workaround for https://github.com/emscripten-core/emscripten/issues/9013
+        if target.contains("emscripten") {
+            cfg.pic(false);
+        }
 
         // We may have found various cross-compilers a little differently due to our
         // extra configuration, so inform gcc of these compilers. Note, though, that

src/librustc_codegen_llvm/llvm_util.rs

@@ -3,7 +3,7 @@ use crate::llvm;
 use syntax_pos::symbol::Symbol;
 use rustc::session::Session;
 use rustc::session::config::PrintRequest;
-use rustc_target::spec::MergeFunctions;
+use rustc_target::spec::{MergeFunctions, PanicStrategy};
 use libc::c_int;
 use std::ffi::CString;
 use syntax::feature_gate::UnstableFeatures;
@@ -73,6 +73,10 @@ unsafe fn configure_llvm(sess: &Session) {
             }
         }
 
+        if sess.target.target.target_os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
+            add("-enable-emscripten-cxx-exceptions");
+        }
+
         // HACK(eddyb) LLVM inserts `llvm.assume` calls to preserve align attributes
         // during inlining. Unfortunately these may block other optimizations.
         add("-preserve-alignment-assumptions-during-inlining=false");

src/librustc_codegen_ssa/back/symbol_export.rs

@@ -364,8 +364,9 @@ fn symbol_export_level(tcx: TyCtxt<'_>, sym_def_id: DefId) -> SymbolExportLevel
         codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL);
 
     if is_extern && !std_internal {
-        // Emscripten cannot export statics, so reduce their export level here
-        if tcx.sess.target.target.options.is_like_emscripten {
+        let target = &tcx.sess.target.target.llvm_target;
+        // WebAssembly cannot export data symbols, so reduce their export level
+        if target.contains("wasm32") || target.contains("emscripten") {
             if let Some(Node::Item(&hir::Item {
                 kind: hir::ItemKind::Static(..),
                 ..

src/librustc_target/spec/wasm32_unknown_emscripten.rs

@@ -9,12 +9,8 @@ pub fn target() -> Result<Target, String> {
                                "-s".to_string(),
                                "ASSERTIONS=1".to_string(),
                                "-s".to_string(),
-                               "DISABLE_EXCEPTION_CATCHING=1".to_string(),
-                               "-s".to_string(),
                                "ABORTING_MALLOC=0".to_string(),
-                               // FIXME(tlively): Enable this linker option once libc type errors
-                               // are resolved. See https://github.com/rust-lang/libc/pull/1478.
-                               // "-Wl,--fatal-warnings".to_string(),
+                               "-Wl,--fatal-warnings".to_string(),
                                ]);
 
     let opts = TargetOptions {
@@ -24,10 +20,7 @@ pub fn target() -> Result<Target, String> {
         linker: None,
         linker_is_gnu: true,
         is_like_emscripten: true,
-        // FIXME(tlively): Emscripten supports unwinding, but we would have to pass
-        // -enable-emscripten-cxx-exceptions to LLVM at codegen time and merge
-        // https://reviews.llvm.org/rG5c3cdef84b82464756bb571c13c31cf7773860c3to use it.
-        panic_strategy: PanicStrategy::Abort,
+        panic_strategy: PanicStrategy::Unwind,
         post_link_args,
         target_family: Some("unix".to_string()),
         .. wasm32_base::options()

src/libtest/lib.rs

@@ -441,9 +441,9 @@ pub fn run_test(
 ) {
     let TestDescAndFn { desc, testfn } = test;
 
-    // FIXME: Re-enable emscripten once it can catch panics again
+    // Emscripten can catch panics but other wasm targets cannot
     let ignore_because_no_process_support = desc.should_panic != ShouldPanic::No
-        && (cfg!(target_arch = "wasm32") || cfg!(target_os = "emscripten"));
+        && cfg!(target_arch = "wasm32") && !cfg!(target_os = "emscripten");
 
     if force_ignore || desc.ignore || ignore_because_no_process_support {
         let message = CompletedTest::new(desc, TrIgnored, None, Vec::new());

src/test/codegen/c-variadic.rs

@@ -1,4 +1,4 @@
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: -C no-prepopulate-passes
 // ignore-tidy-linelength
 

src/test/codegen/drop.rs

@@ -1,4 +1,4 @@
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: -C no-prepopulate-passes
 
 #![crate_type = "lib"]

src/test/codegen/personality_lifetimes.rs

@@ -1,5 +1,5 @@
 // ignore-msvc
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 // compile-flags: -O -C no-prepopulate-passes
 

src/test/codegen/unwind-extern-exports.rs

@@ -1,5 +1,5 @@
 // compile-flags: -C opt-level=0
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![crate_type = "lib"]
 #![feature(unwind_attributes)]

src/test/codegen/unwind-extern-imports.rs

@@ -1,5 +1,5 @@
 // compile-flags: -C no-prepopulate-passes
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![crate_type = "lib"]
 #![feature(unwind_attributes)]

src/test/incremental/change_crate_dep_kind.rs

@@ -1,7 +1,7 @@
 // Test that we detect changes to the `dep_kind` query. If the change is not
 // detected then -Zincremental-verify-ich will trigger an assertion.
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // revisions:cfail1 cfail2
 // compile-flags: -Z query-dep-graph -Cpanic=unwind
 // build-pass (FIXME(62277): could be check-pass?)

src/test/mir-opt/box_expr.rs

@@ -1,4 +1,4 @@
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(box_syntax)]
 

src/test/mir-opt/generator-storage-dead-unwind.rs

@@ -1,4 +1,4 @@
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 // Test that we generate StorageDead on unwind paths for generators.
 //

src/test/mir-opt/issue-41110.rs

@@ -1,4 +1,4 @@
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 // check that we don't emit multiple drop flags when they are not needed.
 

src/test/mir-opt/issue-62289.rs

@@ -1,7 +1,7 @@
 // check that we don't forget to drop the Box if we early return before
 // initializing it
 // ignore-tidy-linelength
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(box_syntax)]
 

src/test/mir-opt/no-spurious-drop-after-call.rs

@@ -1,4 +1,4 @@
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 // Test that after the call to `std::mem::drop` we do not generate a
 // MIR drop of the argument. (We used to have a `DROP(_2)` in the code

src/test/mir-opt/packed-struct-drop-aligned.rs

@@ -1,4 +1,4 @@
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 fn main() {
     let mut x = Packed(Aligned(Droppy(0)));

src/test/mir-opt/remove_fake_borrows.rs

@@ -1,6 +1,6 @@
 // Test that the fake borrows for matches are removed after borrow checking.
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 fn match_guard(x: Option<&&i32>, c: bool) -> i32 {
     match x {

src/test/mir-opt/retag.rs

@@ -1,4 +1,4 @@
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // ignore-tidy-linelength
 // compile-flags: -Z mir-emit-retag -Z mir-opt-level=0 -Z span_free_formats
 

src/test/ui/abi/statics/static-mut-foreign.rs

@@ -5,10 +5,6 @@
 
 // ignore-wasm32-bare no libc to test ffi with
 
-// FIXME: This will work on emscripten once libc is updated to include
-// rust-lang/libc/#1478
-// ignore-emscripten libc type mismatch
-
 #![feature(rustc_private)]
 
 extern crate libc;

src/test/ui/binding/fn-arg-incomplete-pattern-drop-order.rs

@@ -2,7 +2,7 @@
 // Check that partially moved from function parameters are dropped after the
 // named bindings that move from them.
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 use std::{panic, cell::RefCell};
 

src/test/ui/builtin-clone-unwind.rs

@@ -2,7 +2,7 @@
 
 #![allow(unused_variables)]
 #![allow(unused_imports)]
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 // Test that builtin implementations of `Clone` cleanup everything
 // in case of unwinding.

src/test/ui/catch-unwind-bang.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 fn worker() -> ! {
     panic!()

src/test/ui/drop/dynamic-drop-async.rs

@@ -5,7 +5,7 @@
 
 // run-pass
 // edition:2018
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(slice_patterns)]
 #![allow(unused)]

src/test/ui/drop/dynamic-drop.rs

@@ -2,7 +2,7 @@
 #![allow(unused_assignments)]
 #![allow(unused_variables)]
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(generators, generator_trait, untagged_unions)]
 #![feature(slice_patterns)]

src/test/ui/feature-gates/feature-gate-unwind-attributes.rs

@@ -1,4 +1,4 @@
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: -C no-prepopulate-passes -Cpasses=name-anon-globals
 
 #![crate_type = "lib"]

src/test/ui/generator/panic-drops.rs

@@ -1,6 +1,6 @@
 // run-pass
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(generators, generator_trait)]
 

src/test/ui/generator/panic-safe.rs

@@ -1,6 +1,6 @@
 // run-pass
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(generators, generator_trait)]
 

src/test/ui/generator/resume-after-return.rs

@@ -1,6 +1,6 @@
 // run-pass
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(generators, generator_trait)]
 

src/test/ui/issues/issue-14875.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 // Check that values are not leaked when a dtor panics (#14875)
 

src/test/ui/issues/issue-29948.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 use std::panic;
 

src/test/ui/issues/issue-43853.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 use std::panic;
 

src/test/ui/issues/issue-46519.rs

@@ -1,7 +1,7 @@
 // run-pass
 // compile-flags:--test -O
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #[test]
 #[should_panic(expected = "creating inhabited type")]

src/test/ui/iterators/iter-count-overflow-debug.rs

@@ -1,6 +1,6 @@
 // run-pass
 // only-32bit too impatient for 2⁶⁴ items
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: -C debug_assertions=yes -C opt-level=3
 
 use std::panic;

src/test/ui/iterators/iter-position-overflow-debug.rs

@@ -1,6 +1,6 @@
 // run-pass
 // only-32bit too impatient for 2⁶⁴ items
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: -C debug_assertions=yes -C opt-level=3
 
 use std::panic;

src/test/ui/iterators/iter-step-overflow-debug.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: -C debug_assertions=yes
 
 use std::panic;

src/test/ui/iterators/iter-sum-overflow-debug.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: -C debug_assertions=yes
 
 use std::panic;

src/test/ui/iterators/iter-sum-overflow-overflow-checks.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: -C overflow-checks
 
 use std::panic;

src/test/ui/macros/macro-comma-behavior-rpass.rs

@@ -13,7 +13,7 @@
 // compile-flags: --test -C debug_assertions=yes
 // revisions: std core
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![cfg_attr(core, no_std)]
 

src/test/ui/mir/mir_calls_to_shims.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(fn_traits)]
 #![feature(never_type)]

src/test/ui/mir/mir_drop_order.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 use std::cell::RefCell;
 use std::panic;

src/test/ui/never_type/panic-uninitialized-zeroed.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // This test checks that instantiating an uninhabited type via `mem::{uninitialized,zeroed}` results
 // in a runtime panic.
 

src/test/ui/numbers-arithmetic/next-power-of-two-overflow-debug.rs

@@ -1,6 +1,6 @@
 // run-pass
 // compile-flags: -C debug_assertions=yes
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // ignore-emscripten dies with an LLVM error
 
 use std::panic;

src/test/ui/panic-runtime/transitive-link-a-bunch.rs

@@ -4,7 +4,7 @@
 // aux-build:wants-panic-runtime-abort.rs
 // aux-build:panic-runtime-lang-items.rs
 // error-pattern: is not compiled with this crate's panic strategy `unwind`
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![no_std]
 #![no_main]

src/test/ui/panic-runtime/want-unwind-got-abort.rs

@@ -1,7 +1,7 @@
 // error-pattern:is incompatible with this crate's strategy of `unwind`
 // aux-build:panic-runtime-abort.rs
 // aux-build:panic-runtime-lang-items.rs
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![no_std]
 #![no_main]

src/test/ui/panic-runtime/want-unwind-got-abort2.rs

@@ -2,7 +2,7 @@
 // aux-build:panic-runtime-abort.rs
 // aux-build:wants-panic-runtime-abort.rs
 // aux-build:panic-runtime-lang-items.rs
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![no_std]
 #![no_main]

src/test/ui/proc-macro/expand-with-a-macro.rs

@@ -1,7 +1,7 @@
 // run-pass
 // aux-build:expand-with-a-macro.rs
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![deny(warnings)]
 

src/test/ui/reachable-unnameable-items.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // aux-build:reachable-unnameable-items.rs
 
 extern crate reachable_unnameable_items;

src/test/ui/rfc-1937-termination-trait/termination-trait-in-test.rs

@@ -1,7 +1,7 @@
 // compile-flags: --test
 // run-pass
 
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![feature(test)]
 

src/test/ui/rfcs/rfc1857-drop-order.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 
 #![allow(dead_code, unreachable_code)]
 

src/test/ui/test-attrs/test-allow-fail-attr.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: --test
 #![feature(allow_fail)]
 

src/test/ui/test-attrs/test-should-fail-good-message.rs

@@ -1,5 +1,5 @@
 // run-pass
-// ignore-emscripten compiled with panic=abort by default
+// ignore-wasm32-bare compiled with panic=abort by default
 // compile-flags: --test
 #[test]
 #[should_panic(expected = "foo")]

src/tools/compiletest/src/header.rs

@@ -141,10 +141,6 @@ impl EarlyProps {
                 if config.target == "wasm32-unknown-unknown" && config.parse_check_run_results(ln) {
                     props.ignore = Ignore::Ignore;
                 }
-                // FIXME: Re-enable run-fail once panics are handled correctly
-                if config.target.contains("emscripten") && config.mode == common::RunFail {
-                    props.ignore = Ignore::Ignore;
-                }
             }
 
             if (config.mode == common::DebugInfoGdb || config.mode == common::DebugInfoGdbLldb) &&