Consumer-side fallout from #965 (WSC): unconditional Linux deps, missing Apple toggle, silent submodule failures

[v-patrickpe]

Tracking issue for consumer-side fallout from #965 (WebSocket Compression support). Even with compression turned off, consumers must take on new dependencies and submodules. Filing here so the work can be scoped/split.

Gaps identified

• (fixed by companion PR) Linux CMakeLists.txt:84-86 adds websocketpp_websocket.cpp/.h to LINUX_SOURCE_FILES unconditionally. Consumers building with HC_NOWEBSOCKETS still compile the TU and require External/asio + External/websocketpp submodules to be initialized.
• (fixed by companion PR) Build/libHttpClient.Linux/install_dependencies.bash installs zlib1g / zlib1g-dev unconditionally. Should honor HC_NOZLIB and HC_NOWEBSOCKETS.
• Apple has no HC_ENABLE_WEBSOCKET_COMPRESSION toggle. The macro is hard-coded =1 in 4 places in Build/libHttpClient.Apple.C/libHttpClient.xcodeproj/project.pbxproj (iOS/macOS Debug/Release). Other HC_* knobs are exposed as build settings; this one should follow suit.
• Win32 / GDK silent feature loss when boost-wintls submodule is missing. All WSC-related per-file ClCompile entries in Win32.Shared.vcxitems / GDK.Shared.vcxitems are guarded with Exists('$(HCRoot)\External\boost-wintls\include\wintls.hpp') AND HCEnableWebSocketCompression == 'true'. A consumer who forgets git submodule update --init --recursive gets a working build that silently lacks compression. Suggest emitting an MSBuild <Error> (or at least <Warning>) when HCEnableWebSocketCompression=true and the submodule file is absent.
• %(PreprocessorDefinitions) inheritance bug sweep. GDK: add ASIO_DISABLE_SERIAL_PORT to per-file websocketpp_websocket.cpp defines (follow-up to #987) #988 fixes one instance (ASIO_DISABLE_SERIAL_PORT was dropped on the per-file websocketpp_websocket.cpp overrides because shared-items %(PreprocessorDefinitions) doesn't inherit from the consuming project's ItemDefinitionGroup). The same pattern may exist for other per-file overrides added in WebSocket Compression support #965 and should be audited.

Why "turn it off" doesn't free consumers

Platform	Issue
Linux	websocketpp_websocket.cpp is in the source list unconditionally; External/asio + External/websocketpp are in COMMON_INCLUDE_DIRS unconditionally; install_dependencies.bash installs zlib unconditionally.
Win32/GDK	New External/boost-wintls submodule is required for WSC; missing submodule silently disables the feature.
Apple	No off switch at all.

Companion PR

A companion PR addresses the first two checklist items. Filing the others here because they involve broader design decisions (Apple build settings; MSBuild error emission; per-file-defines audit) that may warrant author input.

[v-patrickpe]

Posting findings from local audit + validation work while #990 is in review.

Audit sweep findings (checklist item 5)

Scanned all *.vcxitems files in Build/ for per-file <ClCompile> overrides that use %(PreprocessorDefinitions) (the same inheritance gap fixed in #988 for websocketpp_websocket.cpp).

2 latent instances found with the same pattern:

File	Line	Source
Build/libHttpClient.GDK.Shared/libHttpClient.GDK.Shared.vcxitems	32-35	PlatformComponents_GDK.cpp
Build/libHttpClient.Win32.Shared/libHttpClient.Win32.Shared.vcxitems	23-26	PlatformComponents_Win32.cpp

Both have conditional <PreprocessorDefinitions Condition="..."> blocks ending with ;%(PreprocessorDefinitions) inside <ClCompile Include="..."> per-file overrides. As with the websocketpp_websocket.cpp case, project-level defines from libHttpClient.GDK.props:114 (ASIO_DISABLE_SERIAL_PORT, __WRL_NO_DEFAULT_LIB__, $(libHttpClientDefine)) and libHttpClient.GDK.props:118 (HC_PLATFORM=HC_PLATFORM_GDK, HC_DATAMODEL=HC_DATAMODEL_LLP64) are silently dropped for these TUs.

Why these aren't currently failing the build: PlatformComponents_{Win32,GDK}.cpp apparently don't transitively pull in asio's serial_port_base header (their WSC include of websocketpp_websocket.h is "light" per inspection — only stl headers and internal types). But the latent risk is real: any future define added to GDK.props (e.g., a new platform macro, a new WRL guard) will silently NOT apply to these two TUs, leading to ODR violations or subtle behavioral divergence.

Suggested fix: mirror what #988 did for websocketpp_websocket.cpp — explicitly add the relevant GDK.props defines (ASIO_DISABLE_SERIAL_PORT, HC_PLATFORM=HC_PLATFORM_GDK, HC_DATAMODEL=HC_DATAMODEL_LLP64, __WRL_NO_DEFAULT_LIB__) to the per-file override on PlatformComponents_GDK.cpp, and the Win32 equivalents to PlatformComponents_Win32.cpp. Or — better long-term — restructure to avoid per-file %(PreprocessorDefinitions) overrides in shared-items entirely (e.g., move WSC-conditional defines to a <PropertyGroup> + project-level <ItemDefinitionGroup> driven by HCEnableWebSocketCompression).

Happy to file a follow-up PR for this if you want — but since it's latent and depends on which project-level defines actually matter for these TUs, I'd appreciate input before doing so.

Apple toggle (checklist item 3) — proposed approach

Inspected Build/libHttpClient.Apple.C/libHttpClient.xcodeproj/project.pbxproj. The structure is:

• 22 XCBuildConfiguration entries (11 targets × Debug/Release).
• HC_ENABLE_WEBSOCKET_COMPRESSION=1 appears in 4 of them (the 2 main framework targets × Debug/Release; the same blocks that have HC_LINK_STATIC=1).
• The other 18 build configs (tests, smaller targets) don't define the macro and apparently never have — leaving them as-is preserves current behavior.

Proposed fix:

1. In each of the 4 affected buildSettings = { ... } blocks, add a User-Defined Setting line: HC_ENABLE_WEBSOCKET_COMPRESSION = 1;
2. In the same 4 blocks, change "HC_ENABLE_WEBSOCKET_COMPRESSION=1" to "HC_ENABLE_WEBSOCKET_COMPRESSION=$(HC_ENABLE_WEBSOCKET_COMPRESSION)" in GCC_PREPROCESSOR_DEFINITIONS.

This preserves default-ON behavior and lets consumers override via xcodebuild HC_ENABLE_WEBSOCKET_COMPRESSION=0 or via xcconfig. Pattern matches Xcode's standard way of exposing macros as toggles.

I held off on actually filing this as a PR because pbxproj edits are fragile without local Xcode validation (I'm on Windows; no Xcode access here). If someone with an Apple build env can validate, the edit itself is mechanical.

Local validation of #990 (PR is open)

Ran install_dependencies.bash --check in three modes against my local libHC checkout:

=== Default (expect zlib in dep list) ===
Missing dependency: clang
Missing dependency: make
Missing dependency: autoconf
Missing dependency: automake
Missing dependency: libtool
Missing dependency: zlib1g
Missing dependency: zlib1g-dev

=== HC_NOZLIB=true (expect no zlib) ===
Missing dependency: clang
Missing dependency: make
Missing dependency: autoconf
Missing dependency: automake
Missing dependency: libtool

=== HC_NOWEBSOCKETS=true (expect no zlib) ===
Missing dependency: clang
Missing dependency: make
Missing dependency: autoconf
Missing dependency: automake
Missing dependency: libtool

Behavior matches expectations on all three paths. Default is unchanged from pre-#990.