Add a test that without debuginfo symbols still resolve

Almost all platforms should still have some degree of symbolication
without debug symbols being present (aka the dynamic symbol table and
such), so add a test asserting that symbols do indeed come out in these
scenarios.

This test will likely need to be blacklisted for platforms over time,
but that's ok.

ci/azure-test-all.yml

@@ -41,5 +41,7 @@ steps:
     displayName: "Test backtrace (-default + dbghelp + std + verify-winapi)"
   - bash: cd ./crates/cpp_smoke_test && cargo test
     displayName: "Test cpp_smoke_test"
-  - bash: cd ./crates/without_debuginfo && cargo test
-    displayName: "Test without debuginfo"
+  - bash: cd ./crates/without_debuginfo && cargo test --features libbacktrace
+    displayName: "Test without debuginfo (libbacktrace)"
+  - bash: cd ./crates/without_debuginfo && cargo test --features 'libbacktrace coresymbolication'
+    displayName: "Test without debuginfo (coresymbolication)"

crates/without_debuginfo/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "without_debuginfo"
+version = "0.1.0"
+authors = ["Alex Crichton <[email protected]>"]
+edition = "2018"
+
+[dependencies.backtrace]
+path = "../.."
+default-features = false
+features = [
+  # make sure a trace can be acquired
+  'libunwind',
+  'dbghelp',
+
+  # Allow fallback to dladdr
+  'dladdr',
+
+  # Yes, we have `std`
+  'std',
+]
+
+[profile.dev]
+debug = false
+
+[profile.test]
+debug = false
+
+[features]
+libbacktrace = ['backtrace/libbacktrace']
+coresymbolication = ['backtrace/coresymbolication']

crates/without_debuginfo/src/lib.rs

@@ -0,0 +1 @@
+// intentionally blank

crates/without_debuginfo/tests/smoke.rs

@@ -0,0 +1,19 @@
+#[test]
+fn all_frames_have_symbols() {
+    println!("{:?}", backtrace::Backtrace::new());
+
+    let mut all_have_symbols = true;
+    backtrace::trace(|frame| {
+        let mut any = false;
+        backtrace::resolve_frame(frame, |sym| {
+            if sym.name().is_some() {
+                any = true;
+            }
+        });
+        if !any && !frame.ip().is_null() {
+            all_have_symbols = false;
+        }
+        true
+    });
+    assert!(all_have_symbols);
+}