Build with `-Cpanic=unwind` by default

This doesn't enable unwinding as cg_clif doesn't support it yet. It does
allow for linking to a cg_llvm compiled libstd.so, which uses
`-Cpanic=unwind`.

2 files changed, 15 insertions, 2 deletions

diff --git a/src/bin/cg_clif.rs b/src/bin/cg_clif.rs
index 983839d48d2..0d73834f165 100644
--- a/src/bin/cg_clif.rs
+++ b/src/bin/cg_clif.rs
@@ -24,7 +24,16 @@ impl rustc_driver::Callbacks for CraneliftPassesCallbacks {
         self.time_passes = config.opts.prints.is_empty()
             && (config.opts.debugging_opts.time_passes || config.opts.debugging_opts.time);
 
-        config.opts.cg.panic = Some(PanicStrategy::Abort);
+        if config.opts.test {
+            // Unwinding is not yet supported by cg_clif. `-Cpanic=abort` in combination with
+            // `-Zpanic-abort-tests` ensures that tests are run in a subprocess. This avoids
+            // crashing the test driver on panics, thereby allowing it to report the error and
+            // continue with other tests.
+            config.opts.cg.panic = Some(PanicStrategy::Abort);
+            // Avoid `-Cprefer-dynamic` in case of `-Cpanic=abort` as that will cause a dynamically
+            // linked libstd with `-Cpanic=unwind` to be linked in, which isn't allowed.
+            config.opts.cg.prefer_dynamic = false;
+        }
         config.opts.debugging_opts.panic_abort_tests = true;
         config.opts.maybe_sysroot = Some(config.opts.maybe_sysroot.clone().unwrap_or_else(|| {
             std::env::current_exe().unwrap().parent().unwrap().parent().unwrap().to_owned()
diff --git a/src/bin/cg_clif_build_sysroot.rs b/src/bin/cg_clif_build_sysroot.rs
index e7cd5edbbf6..70e41f9997e 100644
--- a/src/bin/cg_clif_build_sysroot.rs
+++ b/src/bin/cg_clif_build_sysroot.rs
@@ -44,7 +44,11 @@ impl rustc_driver::Callbacks for CraneliftPassesCallbacks {
             return;
         }
 
-        config.opts.cg.panic = Some(PanicStrategy::Abort);
+        if config.opts.crate_name.as_deref() == Some("panic_abort") {
+            // panic_abort must always be built with `-Cpanic=abort`
+            config.opts.cg.panic = Some(PanicStrategy::Abort);
+        }
+
         config.opts.debugging_opts.panic_abort_tests = true;
         config.opts.maybe_sysroot =
             Some(std::env::current_exe().unwrap().parent().unwrap().parent().unwrap().to_owned());