[Mono.Android] CoreCLR: file/line in stack traces with FastDev

[jonathanpeppers]

Why

On CoreCLR with FastDev, runtime-rendered managed stack traces (Environment.StackTrace, Exception.StackTrace) print method names only, even though portable PDBs are deployed alongside the assemblies in files/.__override__/<arch>/. No in File.cs:line N.

Root cause: we resolve FastDev assemblies through host_runtime_contract.external_assembly_probe, which reads the .dll into a heap buffer and hands the bytes to the runtime. The CLR never opens the file itself, so Assembly.Location is empty and StackTraceSymbols has no anchor for finding the sibling .pdb.

dotnet/macios does not have this problem because it lists assemblies in TRUSTED_PLATFORM_ASSEMBLIES with full paths, so the CLR opens them from disk and Assembly.Location is populated.

Approach

In Debug startup, append TRUSTED_PLATFORM_ASSEMBLIES to the properties passed to coreclr_initialize, listing the full on-disk path of every assembly from the build-time typemap (type_map_unique_assemblies) that is also present in the override directory. The CLR then mmap's those files itself via PEImage::OpenImage, which records m_path, populates Assembly.Location, and lets StackTraceSymbols.TryOpenAssociatedPortablePdb find the matching .pdb via simple sibling-file lookup.

• No DebugType change, no opt-in property, no impact on Release builds.
• TPA list is bounded by the build-time typemap, so we never pass arbitrary files from the override directory.
• BCL/framework assemblies (not in the typemap, never pushed via FastDev) keep flowing through the existing external_assembly_probe / AssemblyStore path unchanged.
• Storage for the TPA string and the augmented const char** arrays uses function-local static to satisfy CoreCLR's requirement that the pointers outlive coreclr_initialize.

Test

Adds StackTraceContainsLineNumbers to InstallAndRunTests (CoreCLR, Debug, FastDev): runs an app emitting Environment.StackTrace and asserts logcat contains a frame matching at ...MainActivity.OnCreate... in ...MainActivity.cs:line N.

Related to dotnet/runtime#124087 — this is the dotnet/android-side workaround that does not require changes to the CLR's StackFrameHelper code path.

Checklist

• Useful description of why the change is necessary.
• Links to issues fixed
• Unit tests

[Copilot]

Pull request overview

Improves CoreCLR Debug + FastDev developer experience by enabling portable PDB lookup for runtime-rendered managed stack traces (so Environment.StackTrace / Exception.StackTrace include in File.cs:line N) when assemblies are loaded from the FastDev override directory.

Changes:

• Appends a TRUSTED_PLATFORM_ASSEMBLIES (TPA) list during CoreCLR initialization in Debug+FastDev so CoreCLR opens override assemblies from disk and populates Assembly.Location.
• Adds FastDevAssemblies::build_tpa_list() to construct a bounded TPA list from typemap-known assemblies present in .__override__/<abi>/.
• Adds a device integration test asserting file/line info appears in stack traces under CoreCLR Debug FastDev.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
tests/MSBuildDeviceIntegration/Tests/InstallAndRunTests.cs	Adds a CoreCLR Debug FastDev device test that validates stack traces contain File.cs:line N.
src/native/clr/include/host/fastdev-assemblies.hh	Declares FastDevAssemblies::build_tpa_list() (Debug) with a Release stub.
src/native/clr/host/host.cc	Extends CoreCLR init properties (Debug) to include TPA when FastDev override assemblies are present.
src/native/clr/host/fastdev-assemblies.cc	Implements build_tpa_list() by enumerating typemap-known assemblies and including those found on disk in the override directory.

[jonathanpeppers]

/review

[github-actions]

✅ Android PR Reviewer completed successfully!

[github-actions]

🤖 Android PR Reviewer — ⚠️ Needs Changes

The production change is correct and nicely scoped. A few things I verified that look good:

• build_tpa_list is compiled only in DEBUG_BUILD (src/native/clr/host/CMakeLists.txt), so the type_map* symbols it dereferences are always present — no Release link/ODR hazard.
• Augmentation is gated behind if constexpr (Constants::is_debug_build), and TRUSTED_PLATFORM_ASSEMBLIES is a reserved runtime property (Microsoft.Android.Sdk.RuntimeConfig.targets), so it's filtered out of the generated property list → no duplicate key passed to coreclr_initialize.
• The static storage for the TPA string and the augmented const char** arrays correctly outlives coreclr_initialize; lifetime reasoning is sound.
• TPA is bounded by the build-time typemap and name_length excludes the trailing NUL, so <name> + ".dll" is right.
• Both earlier review notes — asserting #STACKTRACE-END# and checking dirfd() failure — are already addressed in the current diff. 👍

My one blocking concern is device-test determinism (the test reads logcat.log after a capture that stops at Displayed, which races the async stdout→logcat flush of the trace), plus a minor regex-specificity suggestion. Both are inline.

Severity	Count
❌ error	0
⚠️ warning	1
💡 suggestion	1

CI: the Azure DevOps build (dotnet-android) is still in progress at review time — not yet green — so the PR isn't mergeable regardless of the above.

👍 Clear root-cause writeup linking Assembly.Location → StackTraceSymbols portable-PDB sibling lookup, and good instinct to bound the TPA list by the typemap rather than trusting arbitrary files in the override directory.

Generated by Android PR Reviewer for issue #11702 · 1.1K AIC · ⌖ 45.9 AIC · ⊞ 37.8K
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[jonathanpeppers]

/review

[github-actions]

✅ Android PR Reviewer completed successfully!

[github-actions]

🤖 Code Review — CoreCLR: file/line in stack traces with FastDev

Nice, well-scoped change. The design is sound and security-conscious: build_tpa_list derives the TPA set from the trusted build-time typemap (type_map_unique_assemblies) intersected with what's actually present in the per-ABI .__override__ dir, rather than blindly enumerating the override directory — so there's no path-traversal / arbitrary-file surface. Things I verified and liked:

• Correctly gated to Debug. fastdev-assemblies.cc is DEBUG_BUILD-only (CMake) with inline non-DEBUG stubs in the header, and host.cc wraps the new prop-array logic in if constexpr (Constants::is_debug_build). No ODR/link surprises.
• No duplicate runtime property. TRUSTED_PLATFORM_ASSEMBLIES is listed in _RuntimeConfigReservedProperties, so appending it once in host.cc won't collide with a property already passed to coreclr_initialize.
• Resource-clean. build_tpa_list closedirs on every return path; the function-local static prop storage in host.cc is intentional (it must outlive coreclr_initialize) and thread-safe to initialize.
• Small cleanup. Tightened a C-style cast to static_cast<int>(...) along the way.
• Good regression test. StackTraceContainsLineNumbers forces FastDev (EmbedAssembliesIntoApk=false) and asserts a real ...MainActivity.cs:line <N> frame from logcat.

Two minor 💡 suggestions posted inline (no blockers):

1. Document that the feature no-ops when the native typemap is empty (managed/trimmable typemap), since it depends on type_map_unique_assemblies.
2. Use a raw string literal for the injected source, to match the sibling tests in the same file.

Verdict: No blocking issues from me. I'm holding off on a ✅ LGTM only because the internal Azure DevOps PR builds were still in progress at review time (no failures observed) — and this is a device test that needs CI to actually exercise it. Please confirm those go green before merging.

— Issues: 0 ❌ · 0 ⚠️ · 2 💡

Generated by Android PR Reviewer for issue #11702 · 2.4K AIC · ⌖ 47.2 AIC · ⊞ 37.8K
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