Platform Layer

Platform support, POSIX-only subsystems, platform guards, and portability rules.

Platform Support Overview

Platform	Status	Notes
Linux	Full	Primary development platform. All tests pass.
macOS	Full	POSIX-compatible. Same as Linux.
Windows	Partial	The `Net` component links `ws2_32` privately. POSIX-only subsystems remain known gaps.
Android	Partial	The `Storage` component uses SDL3 when selected; SDL3 must be provided by the parent project first.
Emscripten	Partial	Compiles cleanly. Some features throw `PlatformNotSupportedException` at runtime.

POSIX-Only Subsystems

These subsystems currently use POSIX-specific APIs and are documented as known bugs, not completed features:

Subsystem	POSIX API Used	Status
`System::Net::Sockets`	`<sys/socket.h>`, `<unistd.h>`	POSIX-only
`System::IO::RandomAccess`	`pread`, `pwrite`, `fsync`	Done (has Win32 fallback)
`System::AppDomain / AppContext`	`/proc/self/exe`	Linux-only
`System::TimeZoneInfo`	`localtime_r`, `/usr/share/zoneinfo`	POSIX-only

Platform Guard Rules

These rules are enforced project-wide (see CLAUDE.md):

POSIX includes (<unistd.h>, <sys/socket.h>, etc.) must not appear in public .hpp headers.
Platform-specific code lives only in .cpp files.
Use #ifdef _WIN32 / #elif defined(__EMSCRIPTEN__) / #else (POSIX) guards.
On unsupported platforms, throw System::PlatformNotSupportedException with a clear message.
Emscripten builds must compile without errors even when features are runtime-unavailable.

Example Guard Pattern

// In a .cpp file — platform-specific implementation
#ifdef _WIN32
    #include <windows.h>
    // Win32 implementation
#elif defined(__EMSCRIPTEN__)
    throw System::PlatformNotSupportedException("Not available on Emscripten.");
#else
    #include <unistd.h>
    // POSIX implementation
#endif

Windows-Specific

The Net component automatically links ws2_32 privately on Windows. Consumers request SharpRuntime::Net or a higher-level networking component and do not link ws2_32 themselves.

Android-Specific

On Android, SharpRuntime::Storage::StoragePaths uses SDL3 APIs to determine storage paths:

SDL_GetPrefPath() for the isolated storage root
SDL_GetAndroidInternalStoragePath() as fallback

SDL3 headers and library must be available via the parent project before add_subdirectory(sharp-runtime) is called when Storage is selected. The component accepts either SDL3::SDL3 or SDL3::SDL3-static.

Emscripten-Specific

Emscripten (WebAssembly) support requires:

All platform-guarded code must be guarded by #elif defined(__EMSCRIPTEN__)
Features that cannot work in a browser should throw PlatformNotSupportedException
The build must produce zero errors

StoragePaths

modules/storage/include/SharpRuntime/Storage/StoragePaths.hpp | modules/storage/src/SharpRuntime/Storage/StoragePaths.cpp

Provides platform-aware isolated storage paths:

std::filesystem::path root = SharpRuntime::Storage::StoragePaths::GetIsolatedStorageRoot();

Implementation varies by platform: uses SDL_GetPrefPath on Android, appropriate paths on other platforms.

Network Sockets

modules/net-sockets/include/System/Net/Sockets/

Status: POSIX-only

Class	Header
`TcpClient`	`System/Net/Sockets/TcpClient.hpp`
`UdpClient`	`System/Net/Sockets/UdpClient.hpp`
`NetworkStream`	`System/Net/Sockets/NetworkStream.hpp`

These use <sys/socket.h> and related POSIX headers. Windows and Emscripten support is incomplete.

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