Convert non-Windows apphost to C by Copilot · Pull Request #126367 · dotnet/runtime

Copilot · 2026-03-31T18:43:51Z

Convert non-Windows apphost to C. On windows, we still have apphost.windows.cpp and it remains C++. dotnet and singlefilehost also remain C++.

Separate entry points for apphost and dotnet
- apphost entry point is apphost.c, shared by the standalone apphost and singlefilehost.
- dotnet entry point is dotnet.cpp
- Remove corehost.cpp
hostfxr resolvers:
- apphost resolver is now C
- singlefilehost keeps its C++ resolver for statically-linked hostfxr
- dotnet resolver is separate and under the dotnet folder

Create C source files for apphost that replace the C++ implementation: - apphost_main.c: main entry point - apphost_pal.c/h: platform abstraction layer (Unix) - apphost_trace.c/h: tracing system - apphost_utils.c/h: utility functions - apphost_fx_ver.c/h: semantic version parsing - apphost_fxr_resolver.c/h: hostfxr path resolution - apphost_bundle_marker.c/h: bundle detection - apphost_hostfxr_resolver.c/h: hostfxr loading Uses dn-vector from src/native/containers for collections. Windows builds retain existing C++ sources. Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/2c33d365-8b70-4325-8eee-7f004ba86639 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

- Add stddef.h includes for size_t in headers - Fix HAVE_DIRENT_D_TYPE guard to use config.h - Fix dn_vector_at calls to pass element size - Add test_only_getenv for test install location overrides - Add test overrides in pal_get_dotnet_self_registered_dir and pal_get_default_installation_dir - Add ctype.h include for tolower Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/2c33d365-8b70-4325-8eee-7f004ba86639 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

- Remove dead code block (always-false DIR_SEPARATOR check) in apphost_main.c - Remove unused free_string_entry function in apphost_fxr_resolver.c - Add explicit errno.h include in apphost_pal.c Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/2c33d365-8b70-4325-8eee-7f004ba86639 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Move C source files from apphost/standalone/ to hostmisc/: - apphost_trace.c/h, apphost_pal.c/h, apphost_utils.c/h - apphost_fx_ver.c/h, apphost_fxr_resolver.c/h, apphost_bundle_marker.c/h Create hostmisc_c OBJECT library target in hostmisc/CMakeLists.txt with proper include directories and dependencies. Update apphost/standalone/CMakeLists.txt to use hostmisc_c and dn-containers CMake targets instead of compiling C files directly. Add dn-containers subdirectory to corehost and singlefilehost builds for non-Windows platforms. Update apphost_fxr_resolver.c to use <dn-vector.h> include path consistent with the dn-containers CMake target. Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/6be87a85-902f-4646-92e6-2fb6783a5f57 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Rewrite bundle_marker.h as a C++ wrapper around the C implementation in apphost_bundle_marker.c. Add extern "C" guards to apphost_bundle_marker.h for C++ compatibility. Remove bundle_marker.cpp since the C implementation in hostmisc_c (apphost_bundle_marker.c) is now the single source of truth. Update standalone/CMakeLists.txt and static/CMakeLists.txt to use apphost_bundle_marker.c instead of the removed bundle_marker.cpp. Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/65fd3a5e-99f8-4acc-830f-644976f2cfb1 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

…mutex - Removed trace.cpp (C++ implementation) - Updated apphost_trace.h: Added pal_char_t typedef (wchar_t on Windows, char on Unix), extern C guards, va_list function variants - Updated apphost_trace.c: Added Windows support (wide chars, OutputDebugStringW, WriteConsoleW), replaced spinlock with minipal mutex, added _v versions of variadic functions for C++ forwarding - Updated trace.h: Now a thin C++ wrapper calling C functions via va_list - Updated CMakeLists.txt: Use apphost_trace.c instead of trace.cpp, add minipal/mutex.c to both hostmisc and hostmisc_c" Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/2c57cab1-6ebb-4ab7-bbbf-38835b4336b3 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Inline the getenv and xtoi helpers directly in apphost_trace.c to avoid depending on apphost_pal.c which is only in hostmisc_c." Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/2c57cab1-6ebb-4ab7-bbbf-38835b4336b3 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

- trace_error_v: Copy va_list before any consumption to avoid using a consumed va_list (undefined behavior per C11 §7.16.1) - trace_warning: Delegate to trace_warning_v instead of duplicating the implementation inline Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/2c57cab1-6ebb-4ab7-bbbf-38835b4336b3 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

- fx_ver.cpp: Rewrite to delegate to apphost_fx_ver.c for parse(), compare(), and as_str() operations. Handles char/wchar_t conversion for Windows compatibility. - utils.cpp: On non-Windows, delegate get_current_arch_name(), get_runtime_id(), get_host_version_description(), and get_dotnet_root_env_var_for_arch() to apphost_utils.c. - apphost_fx_ver.h: Add extern "C" guards, rename to c_fx_ver_t to avoid collision with C++ fx_ver_t struct. - apphost_utils.h: Add extern "C" guards, guard macros with #ifndef to avoid conflicts with utils.h. - apphost_pal.h: Add extern "C" guards. - CMakeLists.txt: Add apphost_fx_ver.c to all platforms, add apphost_pal.c and apphost_utils.c on non-Windows. Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/15a555ca-6237-4c3e-9a6a-93b3c993d1e9 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

- Revert get_dotnet_root_env_var_for_arch to C++ implementation since the C version ignores the arch parameter - Replace 'auto' with explicit 'pal::char_t' in palstr_to_narrow Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/15a555ca-6237-4c3e-9a6a-93b3c993d1e9 Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

dotnet-policy-service · 2026-03-31T18:56:33Z

Tagging subscribers to this area: @agocke, @jeffschwMSFT, @elinor-fung
See info in area-owners.md if you want to be subscribed.

Rename all hostmisc C files per review feedback: - apphost_trace.c → trace.c, apphost_trace.h → trace_c.h - apphost_fx_ver.c → fx_ver.c, apphost_fx_ver.h → fx_ver_c.h - apphost_pal.c → pal.c, apphost_pal.h → pal_c.h - apphost_utils.c → utils.c, apphost_utils.h → utils_c.h - apphost_fxr_resolver.c → fxr_resolver.c, apphost_fxr_resolver.h → fxr_resolver_c.h - apphost_bundle_marker.c → bundle_marker.c, apphost_bundle_marker.h → bundle_marker_c.h Update all #include directives, CMakeLists.txt references, header guards, and comments to use the new names. Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/869a7b2a-c34a-4b37-ab96-28caca72225e Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Copilot · 2026-03-31T18:59:06Z

@copilot rename the hostmisc C files prefixed with apphost_ to drop the apphost_ prefix. They should be .c versions living next to their corresponding .cpp files. For the header files, they can ha...

Done in 7b1a73c. Renamed all hostmisc C files to drop the apphost_ prefix (e.g., apphost_trace.c → trace.c) and headers to use _c suffix (e.g., apphost_trace.h → trace_c.h). Updated all #include directives, CMakeLists.txt references, and header guards.

Move the pal_char_t typedef from trace_c.h to pal_c.h as the canonical location. Define it cross-platform (wchar_t on Windows, char on non-Windows) with #ifndef guards to avoid redefinition conflicts with pal.h (C++ PAL). Update function signatures in pal_c.h, pal.c, utils_c.h, and utils.c to use pal_char_t instead of raw char for platform string parameters. Make trace_c.h include pal_c.h for the typedef instead of defining it locally. Restructure pal_c.h to be includable on all platforms (cross- platform types at top, POSIX-specific parts guarded with #if !defined(_WIN32)). Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/88526fd5-afd6-42dc-b551-5b6cd904b449 Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Change hostfxr_resolver_t struct to use char* instead of char[4096]. Change fxr_resolver_try_get_path API to return malloc'd strings via char** instead of writing to fixed-size caller-provided buffers. Convert local path buffers in apphost_main.c and fxr_resolver.c to use malloc/free instead of stack-allocated fixed arrays. Add utils_file_exists_in_dir_alloc and utils_get_directory_alloc helpers that return dynamically allocated strings. Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/84b0096a-a181-477e-a6b7-04df74e9919c Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

createdump_static is only built and linked on macOS and non-x86/non-Android Linux, but apphost_static_init's guard had been widened to HOST_UNIX, so it referenced initialize_static_createdump on other Unix targets (e.g. FreeBSD) where the library isn't linked. Define FEATURE_STATIC_CREATEDUMP from the same CMake condition that links createdump_static and gate the call on it, so the guard and the link cannot drift. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…uard - static hostfxr_resolver_init: allocate dotnet_root/fxr_path into locals and assign them into the resolver only after both allocations succeed, so it is never left partially initialized on OOM. - utils_get_host_version_description: guard against a NULL or zero-length output buffer before formatting, matching the other utils_* helpers. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Drop utils_get_host_version_description and emit the version string directly at the trace call: VER_PRODUCTVERSION_STR on Windows, sccsid on Unix. Addresses PR feedback. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 22/22 changed files
Comments generated: 3

- apphost: reject an empty embedded binding, preserving the prior behavior where an empty app DLL name failed conversion on Windows. - pal.windows: initialize the out handle to NULL so callers never observe an uninitialized value after a failed load, and free the loaded module if pinning it fails. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Provide a Unix implementation of pal_utf8_to_palstr (a length-checked copy, since pal_char_t is already UTF-8 char there) so callers no longer need a platform ifdef around the Windows conversion and a Unix memcpy. The embedded-path handling in apphost and the standalone resolver now just call the PAL helper. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Concatenate HOST_VERSION/REPO_COMMIT_HASH (and VER_PRODUCTVERSION_STR on Windows) directly into the trace format string instead of formatting them into a buffer with pal_str_printf. These are all compile-time macros, so the message is built at compile time. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 22/22 changed files
Comments generated: 1

- Use DIR_SEPARATOR directly for the embedded-name separator check instead of probing for both / and \ (the Windows loop above already normalizes / to DIR_SEPARATOR). - Build the app-relative .NET path with the existing utils_append_path_alloc helper instead of open-coding the allocation. - Rename need_newer_framework_error to report_outdated_framework_error and size its download URL buffer with MAX_DOWNLOAD_URL_LEN. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The dotnet muxer's fxr_resolver_try_get_path ignores the search location argument, so the single-use s_dotnet_search_location constant added no value. Pass fxr_search_location_default directly instead. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Cache the bundle_marker_is_bundle() result in exe_start instead of calling it twice. - Use pal_strdup in the static resolver instead of open-coding the size calculation, allocation, and copy. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Hoist the .NET search embed size to a file-scope EMBED_DOTNET_SEARCH_SIZE define so the embed array and the app_relative_dotnet buffer share one constant instead of a duplicated literal. - Drop the unused <cinttypes> include from the dotnet muxer. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 22/22 changed files
Comments generated: 2

Define pal_proc_t (FARPROC on Windows, void* on Unix) mirroring pal::proc_t, and return it from pal_get_symbol. On Windows this removes the union in pal_get_symbol and avoids any data/function pointer conversion: the resolved symbol stays a function pointer that callers cast directly to the target function type. The pal_dll_t and pal_proc_t typedefs live in the existing platform ifdef sections. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 22/22 changed files
Comments generated: 1

- pal_load_library takes a pal_dll_t* instead of void**, so the C++ pal::load_library wrapper no longer reinterpret_casts an HMODULE* to void** and writes a void* through a mismatched pointer type. The apphost resolver's hostfxr handle becomes pal_dll_t to match. - Remove the redundant pal::proc_t typedef; pal::get_symbol returns the C pal_proc_t directly, so no reinterpret_cast is needed. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 22/22 changed files
Comments generated: 0 new

elinor-fung · 2026-07-11T01:38:30Z

@copilot what is the size impact of this change on non-Windows apphosts?

Copilot · 2026-07-11T02:23:31Z

@copilot what is the size impact of this change on non-Windows apphosts?

On a local linux-x64 Release build, comparing the current branch to the pre-PR baseline (ad0692a2a5, before the apphost conversion commits), the non-Windows apphost is smaller now:

apphost: 39,352 -> 31,944 bytes (-7,408, -18.8%)
.text in apphost: 18,330 -> 14,493 (-3,837)
singlefilehost: 10,809,016 -> 10,808,312 bytes (-704, effectively flat)

So the earlier size regression was transient while dn-containers was still in the picture. With the latest branch state, I’m not seeing a net size increase for the non-Windows apphost on Linux.

Copilot AI and others added 10 commits March 27, 2026 05:20

Copilot AI assigned Copilot and jkoritzinsky Mar 31, 2026

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Inline host version at apphost trace site

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Drop utils_get_host_version_description and emit the version string directly at the trace call: VER_PRODUCTVERSION_STR on Windows, sccsid on Unix. Addresses PR feedback. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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This was referenced Jul 3, 2026

[ci-scan] Test failure: System.Threading.Tests.MutexTests.CrossProcess_NamedMutex_ConcurrentCreateOrOpen #130125

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ILC failing with exit code 139 for risc-v build #130145

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Use HOST_VERSION in apphost trace message instead of sccsid

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Include commit hash in apphost trace version message

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Use REPO_COMMIT_HASH for commit in apphost trace version message

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[ci-scan] Test failure: System.Formats.Tar.Tests.TarFile_ExtractToDirectory_File_Tests.ExtractToDirectory_RejectsChainedSymlinkDirectoryTraversal_WithNestedFile #130177

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[wasm] OpenQA.Selenium.WebDriverTimeoutException: timeout: Timed out receiving message from renderer #117486

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Timeout running System.Data.OleDb.Tests #126067

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Wasm.Build.NativeRebuild.Tests.ReferenceNewAssemblyRebuildTest.ReferenceNewAssembly failure: Expected changed file: driver-gen.c #130540

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Copilot AI commented Mar 31, 2026 •

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