Add SYSTEM_CORELIB_DIRECTORY host property for explicit CoreLib location#128734
Merged
Conversation
Adds a new well-known host runtime property, SYSTEM_CORELIB_DIRECTORY, that lets a host explicitly specify the directory containing System.Private.CoreLib.dll. When set, the runtime loads CoreLib from this directory instead of the default lookup beside coreclr, and the single-file bundle-extraction fallback is also skipped. This restores a path-discovery mechanism for hosts (notably mobile platforms like iOS) where CoreCLR is statically linked into the host executable and CoreLib is not located beside it. PR dotnet#128278 removed the previous TPA-scanning fallback in BindToSystem; this replaces it with an explicit, opt-in contract rather than implicit scanning. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Add a Loader test that exercises the new SYSTEM_CORELIB_DIRECTORY host runtime property: copy System.Private.CoreLib.dll into a subdirectory, point the property at that directory, and assert typeof(object).Assembly.Location resolves to the configured directory (and is not the default location beside coreclr). To make corerun usable for testing host-contract-driven features, also extend its host_runtime_contract::get_runtime_property implementation to look up user-defined properties passed via -p/--property. Previously those only flowed to coreclr_initialize (visible via AppContext) but were not exposed through the host runtime contract, so calls to HostInformation::GetProperty from native code returned no value. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Contributor
There was a problem hiding this comment.
Pull request overview
This PR introduces an explicit SYSTEM_CORELIB_DIRECTORY host runtime property so CoreCLR hosts can direct the runtime to load System.Private.CoreLib.dll from a known directory when it is not located beside coreclr.
Changes:
- Adds the new well-known host property definition and documentation.
- Updates CoreCLR system assembly binding to honor the host-provided CoreLib directory and skip the extraction fallback for that path.
- Extends
corerunproperty lookup and adds a Loader test validating the successful override path.
Show a summary per file
| File | Description |
|---|---|
src/native/corehost/host_runtime_contract.h |
Defines the new SYSTEM_CORELIB_DIRECTORY host property. |
src/coreclr/binder/assemblybindercommon.cpp |
Uses the host property to choose the CoreLib lookup directory and gate fallback behavior. |
src/coreclr/hosts/corerun/corerun.cpp |
Makes -p/--property values visible through the host runtime contract callback. |
src/tests/Loader/SystemCoreLibDirectory/SystemCoreLibDirectory.csproj |
Adds the test project setup, host property, and CoreLib copy precommands. |
src/tests/Loader/SystemCoreLibDirectory/SystemCoreLibDirectory.cs |
Verifies CoreLib is loaded from the configured subdirectory. |
docs/design/features/host-runtime-information.md |
Documents the new well-known runtime property. |
Copilot's findings
- Files reviewed: 6/6 changed files
- Comments generated: 3
This was referenced May 29, 2026
Open
Member
|
Just curious why "Directory" why not file path? But now I realize we probably don't want to allow anything to provide a file which is NOT called |
Member
|
@rolfbjarne - for future iOS host changes. |
Member
Author
Yep, that is exactly why I went with directory instead of path. |
vitek-karas
reviewed
May 30, 2026
Co-authored-by: Vitek Karas <10670590+vitek-karas@users.noreply.github.com>
AaronRobinsonMSFT
approved these changes
Jun 2, 2026
Member
Author
|
/ba-g build analysis is stuck, but everything is green. |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Add a new well-known host runtime property,
SYSTEM_CORELIB_DIRECTORY, that lets a host explicitly specify the directory containingSystem.Private.CoreLib.dll. When set, the runtime loads CoreLib from that directory instead of the default lookup besidecoreclr, and the single-file bundle-extraction fallback is also skipped.#128278 removed the TPA-scanning fallback in
BindToSystem, which broke scenarios (notably mobile platforms like iOS) wherecoreclris not next toSystem.Private.CoreLib.dllis not located beside it (see comment on #128278). Rather than restoring implicit scanning, this PR provides an explicit, opt-in contract for hosts to point the runtime at CoreLib.cc @dotnet/appmodel @AaronRobinsonMSFT
Note
This PR was authored with assistance from GitHub Copilot.