refactor: platform abstraction layer + fix macOS stdin hang#55
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New module mcpp.toolchain.msvc with three discovery strategies: 1. vswhere.exe (Microsoft's official VS locator) — most reliable 2. Environment variables (VSINSTALLDIR, VS*COMNTOOLS) 3. Well-known paths (VS 2017-2025, all editions + BuildTools) Replaces the hardcoded VS2022 path in clang.cppm with msvc::find_std_module_source(). Fixes "no std module source" error on machines with non-standard VS installations. Also provides find_cl() for future MSVC toolchain support.
Create a unified platform abstraction layer that consolidates all
platform-specific code into dedicated modules under src/platform/:
- common.cppm: compile-time constants, platform detection, naming
- process.cppm: unified subprocess execution (auto-closes stdin on
POSIX — fixes macOS first-run hang where xcrun/xcode-
select would block waiting for user input)
- fs.cppm: self_exe_path(), which(), RAII FileLock
- shell.cppm: platform-aware shell argument quoting
- env.cppm: environment variable operations
- macos.cppm: Xcode CLT detection, xcrun SDK discovery
- linux.cppm: LD_LIBRARY_PATH construction, runtime lib dirs
- windows.cppm: PATH manipulation
- platform.cppm: facade that re-exports all sub-modules
Migrated consumers:
- config.cppm: use platform::fs::self_exe_path(), which()
- xlings.cppm: use platform::shell, process, env (all raw
popen/system calls removed)
- probe.cppm: use platform::fs::which(), macos::sdk_path(),
linux_::build_ld_library_path_prefix()
- bmi_cache.cppm: use platform::fs::FileLock (RAII)
- ninja_backend.cppm: use platform::fs::self_exe_path()
- clang.cppm: use platform::exe_suffix for tool paths
- cli.cppm: use platform::name constant
Deleted:
- src/platform.cppm: replaced by src/platform/common.cppm
- src/process.cppm: absorbed by src/platform/process.cppm + shell.cppm
Net result: ~550 lines of scattered #ifdef blocks removed, all
subprocess calls now go through platform::process which auto-redirects
stdin from /dev/null on POSIX.
The previous commit removed <cstdio> during cleanup but stderr is still used in ensure_init(), ensure_patchelf(), and ensure_ninja() warning messages.
P0: Remove all #define popen/_popen macros from 6 files — migrate
every raw popen/pclose/std::system call to platform::process APIs.
Files: cli, ninja_backend, msvc, stdmod, pack, publisher, p1689.
Add run_passthrough() and extract_exit_code() to platform::process.
P1: Replace all manual shell quoting #ifdefs in cli.cppm with
platform::shell::quote(). Covers git clone, ninja -C, cmd_run,
cmd_test (5 locations).
P2: Create platform/terminal.cppm — absorbs is_tty() and
terminal_cols() from ui.cppm. Eliminates #ifdef __unix__ blocks.
P3: Move kXpkgPlatform constant to platform::common::xpkg_platform.
resolver.cppm now uses it without #if defined blocks.
P4: Add link strategy constants (supports_full_static, supports_rpath,
needs_explicit_libcxx) to platform::common. flags.cppm now uses
if constexpr instead of #if defined blocks.
P5: Replace #if defined(_WIN32) in xlings.cppm build_command_prefix,
install_with_progress, ensure_init with if constexpr.
P6: Eliminate all #if defined blocks in ninja_backend.cppm rule
generation. Introduce constexpr $toolenv prefix variable, use
if constexpr for platform-specific rules (cp_bmi, scan_deps).
Net: ~440 lines of #ifdef removed, 315 lines of clean constexpr/
platform API code added. Zero raw popen calls remain outside
src/platform/.
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Sunrisepeak
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May 23, 2026
* fix: seal child-process stdin on Windows (first-run hang) mcpp's first-run flow on Windows was hanging at xlings / xim / curl / git grandchildren that block on terminal stdin, forcing users to press Enter repeatedly to advance bootstrap and toolchain install. Root cause: process::seal_stdin was a no-op on Windows, and install_with_progress's direct-install path deliberately bypassed it. The POSIX side has had </dev/null sealing since PR #55 (macOS xcrun hang fix); Windows never received the equivalent fix. PR #57 only suppressed stdout/stderr noise (>/dev/null 2>&1) and did not touch stdin. Changes: - process.cppm: seal_stdin now appends "<NUL" on Windows (matches POSIX behavior). All capture / run_silent / run_streaming / run_passthrough callers gain the protection automatically. - xlings.cppm: install_with_progress's direct path explicitly appends "<NUL" on Windows. POSIX keeps the original behavior conservatively. - shell.cppm: silent_redirect docstring corrected — it never touched stdin, that's seal_stdin's job. Implementation unchanged. Regression coverage: - tests/unit/test_process_seal_stdin.cpp — deterministic reproduction test. Rebinds the test process's own stdin to an open, empty, never-closing pipe, then calls run_silent / capture / run_streaming with a child that reads stdin (more on Windows, cat on POSIX). Without the fix the child would block forever waiting on our pipe; with the fix it reads NUL / /dev/null and exits immediately. 5-second upper bound (real runs complete in <100ms). - ci-windows.yml — adds a step that launches mcpp via System.Diagnostics.Process with RedirectStandardInput=$true (parent holds the child's stdin open but never writes). Runs mcpp --version, mcpp build, mcpp run. Without the fix, any grandchild reading stdin blocks → step times out → CI fails. With the fix → all complete. * ci(windows): convert MCPP_SELF MSYS path → Windows path; rename pwsh $Args Two issues with the regression step from the previous commit (both showed up only on the actual Windows runner, not in local validation): 1. MCPP_SELF was set in an earlier bash step via `pwd` (git-bash) so the value is MSYS-style (e.g. /d/a/mcpp/...). Bash steps tolerate it but pwsh's `&` operator can't exec it ("not recognized as a name of a cmdlet, function, script file, or executable program"). Convert via cygpath -w before use. 2. `$Args` is a PowerShell automatic variable inside function scope; a `param([string]$Args)` does not bind cleanly. Renamed to $McppArgs to avoid the collision (also updated call sites).
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Summary
src/platform/module directory (9 modules: common, process, fs, shell, env, macos, linux, windows, platform facade)/dev/nullon POSIX viaplatform::process#ifdefblocks across 7 consumer filesself_exe_path()(was in config.cppm + ninja_backend.cppm),which()(was in config.cppm + probe.cppm),FileLock(was inline in bmi_cache.cppm), shell quoting (was in xlings.cppm)src/platform.cppmandsrc/process.cppm(fully absorbed)Architecture
Consumers migrated: config, xlings, probe, bmi_cache, ninja_backend, clang, cli.
Test plan