Convert corehost hostmisc trace and fx_ver to C by Copilot · Pull Request #128420 · dotnet/runtime

Copilot · 2026-05-20T23:41:08Z

Split of #126367: converting the trace and fx_ver modules in src/native/corehost/hostmisc from C++ to C, and reshaping pal/utils for a C-callable surface.

These are pieces that both apphost and nethost would need (also, fxr_resolver, but didn't include that yet). My thought is to get the shared pieces in and then the apphost and nethost conversions with their separate sets of complications can be iterated on in parallel.

cc @dotnet/appmodel @AaronRobinsonMSFT

trace
- trace.c replaces trace.cpp
- trace.h exposes a C trace_* API with C++ inline forwarders.
fx_ver
- hostmisc/fx_ver.{c,h} (moved from fxr/) implements the semver parser in C
- fxr/fx_ver.cpp is now a thin C++ wrapper over c_fx_ver_t.
pal / utils:
- pal.h / utils.h reorganized into a C-compatible section and a C++ pal:: section under #ifdef __cplusplus.
- pal.*.c / utils.c provide implementations for functions needed for trace and fx_ver. pal.*.cpp / utils.cpp versions of those functions are wrappers around the C implementations.
build
- minipal linked in for host binaries (minipal_objects for static libraries)

Windows x64 Release

Binary	Main	PR	Δ	%
apphost.exe	146,944	137,728	−9,216	−6.27%
comhost.dll	175,616	166,400	−9,216	−5.25%
dotnet.exe	148,992	135,168	−13,824	−9.28%
hostfxr.dll	342,528	340,992	−1,536	−0.45%
hostpolicy.dll	344,576	342,528	−2,048	−0.59%
ijwhost.dll	119,296	109,056	−10,240	−8.58%
nethost.dll	102,912	89,088	−13,824	−13.43%
singlefilehost.exe	10,374,144	10,372,096	−2,048	−0.02%

Linux x64 Release

Binary	Main	PR	Δ	%
apphost	74,544	71,792	−2,752	−3.69%
dotnet	54,936	52,552	−2,384	−4.34%
libhostfxr.so	321,280	320,352	−928	−0.29%
libhostpolicy.so	306,704	305,552	−1,152	−0.38%
libnethost.so	70,624	67,824	−2,800	−3.96%
singlefilehost	10,790,224	10,789,264	−960	−0.01%

Static libraries (libhostfxr.a/lib and libnethost.a/lib) do grow due to including minipal_objects - consumers can (probably should) link with dead code elimination.

Replaces trace.cpp with a pure-C trace.c implementation. The trace module is now C end-to-end on every platform: pal.windows.c and pal.unix.c are pure C calling Win32/POSIX directly, with no C++ in the trace call path. Key changes: * trace.cpp removed; trace.c provides trace_setup/enable/is_enabled/ verbose/info/warning/error/println/println_empty/flush plus the va_list variants (trace_*_v) and trace_set/get_error_writer. * trace.h keeps the trace::* C++ namespace as inline forwarders to the new trace_* C functions, so existing corehost C++ callers continue to work without source changes. * pal.h reorganized into a C-compatible section at the top (pal_char_t, _X with two-step expansion for C-mode MSVC, PAL_THREAD_LOCAL, APPHOST_PATH_MAX, DIR_SEPARATOR_STR, pal_str_* macros, extern \"C\" decls for pal_get_own_executable_path/pal_directory_exists/pal_getenv/ pal_xtoi) plus the existing pal:: namespace gated under #ifdef __cplusplus. * pal.unix.c provides the four pal_* functions trace.c needs on POSIX. pal.windows.c provides pal_get_own_executable_path (via GetModuleFileNameW) and pal_directory_exists (GetFileAttributesW + FILE_ATTRIBUTE_DIRECTORY check, matching Unix S_ISDIR semantics). pal_getenv and pal_xtoi are static inline in pal.h on Windows. * utils.h gates its C++ surface under #ifdef __cplusplus and adds an extern \"C\" declaration of utils_get_filename, used by trace.c when TRACEFILE points to a directory. utils.c implements just that one helper. * The original spin lock (std::atomic_flag) is replaced with minipal_mutex, lazy-initialized via InitOnceExecuteOnce on Windows and pthread_once on POSIX. The corehost root CMakeLists.txt now adds the minipal subdirectory; hostmisc/hostmisc_public link against minipal/minipal_objects (gated NOT CLR_CMAKE_TARGET_BROWSER), and libnethost/libhostfxr static archives bundle minipal_objects so the symbols ship in the public archives. * Trace behavior is preserved including the 'Tracing enabled @ <timestamp>' log line (a small strftime helper in trace.c emits the same UTC GMT format as the original pal::get_timestamp). * trace_enable now detects truncation when constructing the per-PID trace path and reports it as a file open error rather than silently using a bad path. trace_error_v emits a fixed fallback message via stderr/error_writer if format/allocation fails, matching the old C++ behavior where such failures propagated as exceptions. First split of #126367 (rest of the C-conversion work follows). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Moves the fx_ver semver parsing/comparison logic from the C++ class to a pure-C implementation in hostmisc/fx_ver.c. The C++ `fx_ver_t` class is preserved as a thin wrapper that delegates to the new `c_fx_ver_*` API, so existing C++ callers compile unchanged. Key changes: * New `hostmisc/fx_ver.h`: declares `c_fx_ver_t` + `c_fx_ver_init/ cleanup/set/is_empty/parse/compare/as_str` in an `extern \"C\"` block, with the existing `fx_ver_t` C++ class declarations gated under`#ifdef __cplusplus`. * New `hostmisc/fx_ver.c`: ports parse_internal, valid_identifier(s), try_stou, index_of_non_numeric, get_id_len, c_fx_ver_compare, and c_fx_ver_as_str using pal_char_t buffers + malloc/free for owned strings. The structure mirrors the original C++ logic. * Rewritten `fxr/fx_ver.cpp`: every member function (constructors, operators, as_str, compare, parse) now delegates to the C functions. `as_str`/`compare` borrow `pal::string_t::c_str()` pointers into a stack-allocated `c_fx_ver_t` (no allocation, no cleanup); `parse` copies the C-allocated strings out into `pal::string_t` and calls `c_fx_ver_cleanup`. Drops the validate-in-constructor `assert`s (they referenced the now-static C helpers). * `hostmisc/pal.h` adds three more C-callable string macros that fx_ver.c needs: `pal_strchr`, `pal_strncmp`, `pal_strtoul`. * CMake plumbing: `hostmisc/CMakeLists.txt` adds `fx_ver.c` and lists `fx_ver.h` in HEADERS; `hostcommon/files.cmake` and the test `test/fx_ver/CMakeLists.txt` are updated to point at the new `hostmisc/fx_ver.h` location. Validation: * Native host build clean on Windows Release (host subset). * Dedicated `test_fx_ver` semver test passes (exit code 0) against the new C-backed implementation. Second split of #126367. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Introduces a C-callable pal_getenv that returns a heap-allocated copy of the named environment variable's value (or NULL if unset/empty). The caller is responsible for free()ing the returned pointer. Matches the existing C++ pal::getenv semantics, which always allocates into a pal::string_t. Choosing the always-allocate API keeps the surface small (one parameter, one return) and lets call sites use a single unconditional free() for cleanup. Also replaces trace.c's get_host_env_var with a thin DOTNET_HOST_<name> / COREHOST_<name> fallback wrapper around pal_getenv. trace_setup and trace_enable now use the heap-allocated values directly and free() them at the end of the call. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Four spots in trace.c had if/else pairs where both branches were single statements with no braces. Add braces consistently so every if/else in the new C code follows the 'if there is an else, both branches are braced' rule. No behavior change. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Moves the two remaining ifdef'd platform-specific calls in trace.c into pal.h as macros, alongside the existing pal_xtoi / pal_str* family: * pal_get_pid() -> ((int)GetCurrentProcessId()) / ((int)getpid()) * pal_file_open(p, m) -> _wfsopen(p, m, _SH_DENYNO) / fopen(p, m) trace.c no longer needs to ifdef around get-pid or fopen, and the Windows-only <share.h> / Unix-only <unistd.h> includes drop out of trace.c (share.h is now pulled in via pal.h's Windows section). No behavior change. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Replaces the bodies of the C++ pal:: implementations with calls to the new C pal_* APIs: * pal::is_directory -> pal_directory_exists (both) * pal::getenv -> pal_getenv (both) * pal::get_own_executable_path -> pal_get_own_executable_path (both) Where the original C++ behavior went beyond what the previous C contract supported, the C side is extended so the C++ wrappers can stay trivial: * pal_get_own_executable_path is now an always-allocate API (returns pal_char_t* / NULL, caller frees) -- consistent with pal_getenv. On Windows it does the GetModuleFileNameW doubling-buffer loop (starting at MAX_PATH = 260) that the prior GetModuleFileNameWrapper had, so paths longer than the old APPHOST_PATH_MAX still work and short paths use a smaller initial allocation than the old 4 KB std::vector wrapper. On Unix it just returns the malloc'd result of minipal_getexepath. trace.c is updated for the new signature (free the result). * pal_getenv on Windows now emits trace_warning on non-ERROR_ENVVAR_NOT_FOUND GetEnvironmentVariableW failures, matching the warning the C++ pal::getenv used to emit. Putting the warning inside pal_getenv (rather than capturing GetLastError after it returns NULL in the C++ wrapper) avoids any fragility around malloc/free perturbing GetLastError. Pure-define wrappers (pal_strlen, pal_str_printf, pal_xtoi, pal_get_pid, pal_file_open, etc.) are intentionally not delegated -- they are already trivial macros and the C++ pal:: inlines compile to the same calls. No behavior change. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: elinor-fung <47805090+elinor-fung@users.noreply.github.com>

Copilot

Pull request overview

This PR continues the corehost “hostmisc” C-migration by replacing the existing C++ trace implementation with a C implementation + C-callable header surface, and by moving the SemVer parser (fx_ver) into a C implementation with a thin C++ wrapper retained for existing callers. It also reshapes pal / utils so they can be consumed from C code, and updates CMake wiring to pull in minipal/minipal_objects where needed.

Changes:

Replace hostmisc/trace.cpp with hostmisc/trace.c and expose a C trace_* API in trace.h (with inline C++ shims for existing trace:: callers).
Move SemVer parsing into hostmisc/fx_ver.{c,h} (C API) and rework fxr/fx_ver.cpp into a C++ wrapper over c_fx_ver_*.
Add/adjust C PAL + utils helpers and update CMake to include/link minipal/minipal_objects for host binaries/static libraries.

Show a summary per file

File	Description
src/native/minipal/CMakeLists.txt	Disables `CMAKE_INCLUDE_CURRENT_DIR` in minipal directory scope.
src/native/corehost/CMakeLists.txt	Adds `minipal` subdirectory to non-browser corehost builds.
src/native/corehost/hostmisc/CMakeLists.txt	Switches hostmisc sources to C implementations and wires `minipal`/`minipal_objects` linkage (non-browser).
src/native/corehost/hostmisc/pal.h	Reorganizes into a C-compatible section plus C++ `pal::` section under `__cplusplus`.
src/native/corehost/hostmisc/pal.windows.c	Adds Windows C implementations for `pal_getenv`, `pal_get_own_executable_path`, `pal_directory_exists`.
src/native/corehost/hostmisc/pal.unix.c	Adds Unix C implementations for `pal_getenv`, `pal_get_own_executable_path`, `pal_directory_exists`.
src/native/corehost/hostmisc/pal.windows.cpp	Redirects selected C++ `pal::` functions to the new C implementations.
src/native/corehost/hostmisc/pal.unix.cpp	Redirects selected C++ `pal::` functions to the new C implementations.
src/native/corehost/hostmisc/utils.h	Makes header C-safe (guards C++-only pieces) and declares `utils_get_filename` for C callers.
src/native/corehost/hostmisc/utils.c	Adds C implementation of `utils_get_filename` used by `trace.c`.
src/native/corehost/hostmisc/trace.h	Introduces a C `trace_*` API and C++ inline forwarders for `trace::`.
src/native/corehost/hostmisc/trace.c	New C implementation of trace functionality (locking, env var reading, output).
src/native/corehost/hostmisc/fx_ver.h	New C SemVer API (`c_fx_ver_*`) plus C++ `fx_ver_t` wrapper declaration.
src/native/corehost/hostmisc/fx_ver.c	New C SemVer parsing/comparison implementation.
src/native/corehost/fxr/fx_ver.cpp	Replaces prior C++ semver logic with a thin wrapper over `c_fx_ver_*`.
src/native/corehost/hostcommon/files.cmake	Updates include/header list to reference moved `hostmisc/fx_ver.h`.
src/native/corehost/nethost/CMakeLists.txt	Adds `minipal_objects` to static lib link line.
src/native/corehost/fxr/staticlib/CMakeLists.txt	Adds `minipal_objects` to static libhostfxr link line.
src/native/corehost/test/fx_ver/CMakeLists.txt	Updates include path for the relocated `fx_ver.h`.
src/native/corehost/hostmisc/trace.cpp	Removed (replaced by `trace.c`).
src/native/corehost/fxr/fx_ver.h	Removed (replaced by `hostmisc/fx_ver.h`).

Copilot's findings

Files reviewed: 21/21 changed files
Comments generated: 2

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

Copilot

Copilot's findings

Files reviewed: 21/21 changed files
Comments generated: 1

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

Initial plan

f34d5d7

Copilot AI assigned Copilot and elinor-fung May 20, 2026

Copilot AI review requested due to automatic review settings May 20, 2026 23:41

github-project-automation Bot added this to AppModel May 20, 2026

Copilot AI review requested due to automatic review settings May 20, 2026 23:41

Copilot started work on behalf of elinor-fung May 20, 2026 23:41 View session

Copilot AI changed the title ~~[WIP] Implement trace conversion in hostmisc files~~ Break out hostmisc C conversion slice (trace + fx_ver + PAL delegation) May 20, 2026

Copilot finished work on behalf of elinor-fung May 20, 2026 23:46

Copilot AI requested a review from elinor-fung May 20, 2026 23:46

github-actions Bot added the area-PAL-coreclr only for closed issues label May 21, 2026

elinor-fung added area-Host and removed area-PAL-coreclr only for closed issues labels May 21, 2026

Copilot started work on behalf of elinor-fung May 21, 2026 19:18 View session

elinor-fung and others added 6 commits May 21, 2026 19:25

Copilot AI requested review from Copilot and removed request for Copilot May 21, 2026 19:26

Copilot AI changed the title ~~Break out hostmisc C conversion slice (trace + fx_ver + PAL delegation)~~ Convert corehost hostmisc trace and fx_ver to C May 21, 2026

Copilot finished work on behalf of elinor-fung May 21, 2026 19:26

elinor-fung marked this pull request as ready for review May 22, 2026 16:32

Copilot AI review requested due to automatic review settings May 22, 2026 16:32

Copilot started reviewing on behalf of elinor-fung May 22, 2026 16:32 View session

Copilot AI reviewed May 22, 2026

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Comment thread src/native/corehost/fxr/fx_ver.cpp

Comment thread src/native/corehost/fxr/fx_ver.cpp Outdated

Copilot started work on behalf of elinor-fung May 22, 2026 18:28 View session

Fix fx_ver constructor invariants and as_str truncation checks

74859c5

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

Copilot finished work on behalf of elinor-fung May 22, 2026 18:39

Copilot started work on behalf of elinor-fung May 22, 2026 18:46 View session

Gate fx_ver as_str truncation assert behind _DEBUG

0d27f4d

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

Copilot AI requested review from Copilot and removed request for Copilot May 22, 2026 18:54

Copilot finished work on behalf of elinor-fung May 22, 2026 18:55

elinor-fung reviewed May 22, 2026

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Comment thread src/native/corehost/fxr/fx_ver.cpp Outdated

Apply suggestion from @elinor-fung

0600d1a

Copilot AI review requested due to automatic review settings May 22, 2026 19:06

Copilot started reviewing on behalf of elinor-fung May 22, 2026 19:06 View session

elinor-fung mentioned this pull request May 22, 2026

Rewrite hostmisc C++ components to wrap C implementations #126367

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Copilot AI reviewed May 22, 2026

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Comment thread src/native/corehost/hostmisc/pal.windows.c

Copilot started work on behalf of elinor-fung May 22, 2026 19:23 View session

Suppress warnings for empty env var values in pal_getenv

5b6f4f5

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

Copilot finished work on behalf of elinor-fung May 22, 2026 19:31

Copilot AI requested a review from elinor-fung May 22, 2026 19:31

This was referenced May 23, 2026

tracing/runtimeeventsource/nativeruntimeeventsource/nativeruntimeeventsource failing in CI #90605

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Test failure: System.Runtime.InteropServices.JavaScript.Tests.YieldAwaitableTests.TaskYieldsToBrowserLoop #127623

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Convert corehost hostmisc trace and fx_ver to C#128420

Convert corehost hostmisc trace and fx_ver to C#128420
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Copilot AI commented May 20, 2026 •

edited by elinor-fung

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edited by elinor-fung

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