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Armor shared libraries with symbol visibility; add _internal companions and build-type-aware optimizations (#322)
* Enforces hidden-by-default symbol visibility on Phlex shared libraries * Introduces non-installed `_internal` companion libraries for testing and comparison * Adds optimization flags that automatically exploit the visibility model Specifically: * `Modules/private/PhlexSymbolVisibility.cmake` supplies the CMake machinery for symbol-hiding * `Modules/private/PhlexOptimization.cmake` supplies the CMake machinery for optimization * Non-template classes and free functions intended for public use (with .cpp implementations) are annotated with a `phlex_X_EXPORT` macro * Template classes and header-only code remains unannotated --------- Co-authored-by: Chris Green <greenc@fnal.gov> Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: greenc-FNAL <2372949+greenc-FNAL@users.noreply.github.com> Co-authored-by: Kyle Knoepfel <knoepfel@fnal.gov>
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‎CMakeLists.txt‎

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@@ -89,8 +89,12 @@ set(CTEST_TEST_TIMEOUT 90 CACHE STRING "Per-test timeout (s) for CTest")
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# Make tools available
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FetchContent_MakeAvailable(Catch2 GSL mimicpp)
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# Avoid use of __COUNTER__ to prevent -pedantic warnings in Catch2's TEST_CASE macro
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set(CATCH_CONFIG_COUNTER OFF)
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include(Modules/private/CreateCoverageTargets.cmake)
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include(Modules/private/PhlexSymbolVisibility.cmake)
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include(Modules/private/PhlexOptimization.cmake)
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option(ENABLE_TSAN "Enable Thread Sanitizer" OFF)
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option(ENABLE_ASAN "Enable Address Sanitizer" OFF)

‎Modules/private/PhlexOptimization.cmake‎

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# Provides phlex_apply_optimizations(target), which applies safe,
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# performance-oriented compiler flags to a Phlex shared library target.
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# Also defines the PHLEX_HIDE_SYMBOLS and PHLEX_ENABLE_IPO options and
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# documents how they interact.
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#
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# Two flags are applied (subject to compiler support and platform):
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#
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# -fno-semantic-interposition (GCC >= 9, Clang >= 8)
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# The compiler may assume that exported symbols in this shared library are
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# not overridden at runtime by LD_PRELOAD or another DSO. This is the
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# natural complement of -fvisibility=hidden: once the exported-symbol
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# surface is bounded by explicit export macros, treating those symbols as
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# non-interposable allows the compiler to inline, devirtualise, and
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# generate direct (non-PLT) calls for same-DSO accesses to exported
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# functions.
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#
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# External plugins continue to call Phlex symbols through the standard
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# PLT/GOT mechanism; only code compiled as part of a Phlex shared library
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# itself benefits.
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#
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# Applied only when PHLEX_HIDE_SYMBOLS=ON (export macros are present and
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# the exported-symbol set is well-defined).
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#
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# -fno-plt (GCC >= 7.3, Clang >= 4, ELF platforms)
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# Calls FROM a Phlex library TO symbols in other shared libraries (TBB,
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# Boost, spdlog, ...) bypass the PLT stub and load the target address
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# directly from the GOT. This replaces one level of indirection on every
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# cross-DSO call after first resolution. Semantics are unchanged; only
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# the dispatch mechanism differs.
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#
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# Not applied on Apple platforms: Mach-O uses two-level namespaces and the
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# PLT abstraction does not map directly to ELF semantics.
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#
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# Intentionally excluded:
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# -ffast-math / -funsafe-math-optimizations
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# Physics and numerical code relies on well-defined floating-point
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# semantics (NaN propagation, exact rounding, signed-zero behaviour).
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# These flags may silently produce incorrect numerical results and are
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# therefore not enabled.
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#
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# Options and their interaction with CMAKE_BUILD_TYPE
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#
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# Both PHLEX_HIDE_SYMBOLS and PHLEX_ENABLE_IPO are defined here so that their
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# defaults can be derived together. The effective defaults are:
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#
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# CMAKE_BUILD_TYPE PHLEX_ENABLE_IPO PHLEX_HIDE_SYMBOLS
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# ───────────────── ─────────────── ─────────────────
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# Release ON ON
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# RelWithDebInfo ON ON
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# Debug / sanitizer OFF OFF
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# not set OFF OFF
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#
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# Both options can be overridden independently on the command line:
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#
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# -DPHLEX_HIDE_SYMBOLS=ON -DPHLEX_ENABLE_IPO=ON → LTO + -fno-semantic-interposition
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# (maximum optimization)
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# -DPHLEX_HIDE_SYMBOLS=OFF -DPHLEX_ENABLE_IPO=ON → LTO only; -fno-semantic-interposition
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# is NOT applied (valid, useful for
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# benchmarking against the ON case)
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# -DPHLEX_HIDE_SYMBOLS=ON -DPHLEX_ENABLE_IPO=OFF → -fno-semantic-interposition only
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# -DPHLEX_HIDE_SYMBOLS=OFF -DPHLEX_ENABLE_IPO=OFF → no special optimization flags
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#
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# The per-target flags in phlex_apply_optimizations() self-adjust automatically
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# to reflect whichever combination is in effect.
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#
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# PHLEX_ENABLE_IPO (default ON for Release/RelWithDebInfo, OFF otherwise)
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# When ON, enables interprocedural optimization (LTO) for Release and
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# RelWithDebInfo configurations. LTO is safe with or without symbol hiding
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# because export attributes preserve the complete exported-symbol set.
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# External plugins compiled without LTO link against the normal
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# exported-symbol table and are unaffected.
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#
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# PHLEX_HIDE_SYMBOLS (default ON for Release/RelWithDebInfo, OFF otherwise)
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# When ON: hidden-by-default visibility; export macros mark the public API.
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# When OFF: all symbols visible; _internal targets become thin INTERFACE
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# aliases of their public counterparts.
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include_guard()
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include(CheckCXXCompilerFlag)
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# Probe flag availability once at module-load time (results are cached in the
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# CMake cache and reused across reconfigures).
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if(NOT APPLE)
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check_cxx_compiler_flag("-fno-plt" PHLEX_CXX_HAVE_NO_PLT)
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# Apple/Clang accepts -fno-semantic-interposition but the Apple toolchain
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# driver treats it as unused for Mach-O builds.
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check_cxx_compiler_flag("-fno-semantic-interposition" PHLEX_CXX_HAVE_NO_SEMANTIC_INTERPOSITION)
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endif()
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# ---------------------------------------------------------------------------
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# Interprocedural optimization (LTO) — defined first so its value can inform
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# the PHLEX_HIDE_SYMBOLS default below.
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# ---------------------------------------------------------------------------
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cmake_policy(SET CMP0069 NEW)
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include(CheckIPOSupported)
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if(CMAKE_BUILD_TYPE MATCHES "^(Release|RelWithDebInfo)$")
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set(_phlex_ipo_default ON)
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else()
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set(_phlex_ipo_default OFF)
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endif()
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option(
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PHLEX_ENABLE_IPO
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[=[Enable interprocedural optimization (LTO) for Release and RelWithDebInfo
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builds. Defaults to ON when CMAKE_BUILD_TYPE is Release or RelWithDebInfo.
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Can be combined with PHLEX_HIDE_SYMBOLS=ON for maximum optimization, or with
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PHLEX_HIDE_SYMBOLS=OFF to benchmark LTO benefit without symbol hiding.]=]
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"${_phlex_ipo_default}"
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)
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# ---------------------------------------------------------------------------
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# Symbol hiding — default follows CMAKE_BUILD_TYPE independently of IPO.
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# The two options are orthogonal: both ON/OFF combinations are valid and
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# produce different optimization profiles for benchmarking.
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# ---------------------------------------------------------------------------
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if(CMAKE_BUILD_TYPE MATCHES "^(Release|RelWithDebInfo)$")
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set(_phlex_hide_default ON)
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else()
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set(_phlex_hide_default OFF)
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endif()
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option(
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PHLEX_HIDE_SYMBOLS
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[=[Hide non-exported symbols in shared libraries (ON = curated API with
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hidden-by-default visibility; OFF = all symbols visible). Defaults to ON for
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Release/RelWithDebInfo builds.
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When ON, -fno-semantic-interposition is also applied (when supported) because
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the exported-symbol surface is explicitly bounded by export macros. This flag
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is independent of PHLEX_ENABLE_IPO; either option may be set without the other.
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Setting OFF while PHLEX_ENABLE_IPO=ON is valid and useful for comparing LTO
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performance with and without symbol hiding.]=]
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"${_phlex_hide_default}"
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)
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# ---------------------------------------------------------------------------
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# Activate LTO (if enabled and supported)
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# ---------------------------------------------------------------------------
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if(PHLEX_ENABLE_IPO)
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check_ipo_supported(RESULT _phlex_ipo_supported OUTPUT _phlex_ipo_output LANGUAGES CXX)
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if(_phlex_ipo_supported)
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# Set defaults for all targets created in this scope and below. The
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# *_RELEASE and *_RELWITHDEBINFO variants leave Debug/Coverage/sanitizer
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# builds unaffected (those configs override optimization independently).
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set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE ON)
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set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELWITHDEBINFO ON)
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message(STATUS "Phlex: LTO enabled for Release and RelWithDebInfo builds")
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else()
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message(WARNING "Phlex: PHLEX_ENABLE_IPO=ON but LTO is not supported: ${_phlex_ipo_output}")
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endif()
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endif()
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# ---------------------------------------------------------------------------
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function(phlex_apply_optimizations target)
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# -fno-semantic-interposition pairs with PHLEX_HIDE_SYMBOLS: the compiler
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# may only treat exported symbols as non-interposable once the exported-
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# symbol surface has been explicitly bounded by export macros.
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if(PHLEX_HIDE_SYMBOLS AND PHLEX_CXX_HAVE_NO_SEMANTIC_INTERPOSITION)
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target_compile_options("${target}" PRIVATE "-fno-semantic-interposition")
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endif()
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# -fno-plt reduces cross-DSO call overhead on ELF (Linux) platforms.
166+
if(PHLEX_CXX_HAVE_NO_PLT)
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target_compile_options("${target}" PRIVATE "-fno-plt")
168+
endif()
169+
endfunction()

‎Modules/private/PhlexSymbolVisibility.cmake‎

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include(GenerateExportHeader)
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function(phlex_apply_symbol_visibility target)
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set(EXPORT_HEADER "${PROJECT_BINARY_DIR}/include/phlex/${target}_export.hpp")
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set(EXPORT_MACRO_NAME "${target}_EXPORT")
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7+
generate_export_header(
8+
${target}
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BASE_NAME ${target}
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EXPORT_FILE_NAME ${EXPORT_HEADER}
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EXPORT_MACRO_NAME ${EXPORT_MACRO_NAME}
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STATIC_DEFINE "${target}_STATIC_DEFINE"
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)
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if(PHLEX_HIDE_SYMBOLS)
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set_target_properties(
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${target}
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PROPERTIES CXX_VISIBILITY_PRESET hidden VISIBILITY_INLINES_HIDDEN ON
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)
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endif()
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target_include_directories(${target} PUBLIC $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/include>)
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install(FILES "${EXPORT_HEADER}" DESTINATION include/phlex)
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endfunction()
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# Create a companion library <target>_internal:
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#
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# When PHLEX_HIDE_SYMBOLS is ON (default): a non-installed shared library with
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# default (visible) symbol visibility, compiled from the same sources as
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# <target>. This allows tests to access non-exported implementation details
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# without requiring every internal symbol to carry an EXPORT macro, and enables
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# before/after comparison of library/executable sizes and link/load times.
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#
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# When PHLEX_HIDE_SYMBOLS is OFF: an INTERFACE target that simply links to
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# <target>. Since all public library symbols are already visible in this mode,
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# no separate compilation is needed and _internal targets are effectively
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# identical to their public counterparts.
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#
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# Usage (in the same CMakeLists.txt that defines <target>):
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# phlex_make_internal_library(<target> LIBRARIES [PUBLIC ...] [PRIVATE ...])
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#
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# The LIBRARIES arguments mirror those of the original cet_make_library call but
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# may substitute other _internal targets for the corresponding public ones so
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# that the full transitive symbol set is visible (PHLEX_HIDE_SYMBOLS=ON only).
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function(phlex_make_internal_library target)
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cmake_parse_arguments(ARG "" "" "LIBRARIES" ${ARGN})
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set(internal "${target}_internal")
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if(NOT PHLEX_HIDE_SYMBOLS)
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# All public symbols already visible — _internal is a thin INTERFACE wrapper.
53+
add_library(${internal} INTERFACE)
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target_link_libraries(${internal} INTERFACE ${target})
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return()
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endif()
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# Retrieve sources and source directory from the public target so we don't
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# have to maintain a separate source list.
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get_target_property(srcs ${target} SOURCES)
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if(NOT srcs)
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message(FATAL_ERROR "phlex_make_internal_library: ${target} has no SOURCES property")
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endif()
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get_target_property(src_dir ${target} SOURCE_DIR)
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get_target_property(bin_dir ${target} BINARY_DIR)
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# Convert relative paths to absolute. Generated sources (e.g. configure_file
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# output) live in the binary directory rather than the source directory.
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set(abs_srcs "")
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foreach(s IN LISTS srcs)
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if(IS_ABSOLUTE "${s}")
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list(APPEND abs_srcs "${s}")
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elseif(EXISTS "${src_dir}/${s}")
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list(APPEND abs_srcs "${src_dir}/${s}")
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else()
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list(APPEND abs_srcs "${bin_dir}/${s}")
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endif()
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endforeach()
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# Use add_library directly (not cet_make_library) so that cetmodules does not
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# register this target for installation or package export.
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add_library(${internal} SHARED ${abs_srcs})
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if(ARG_LIBRARIES)
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target_link_libraries(${internal} ${ARG_LIBRARIES})
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endif()
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# Cetmodules automatically adds $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}> for
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# libraries it manages; replicate that here so consumers (e.g. layer_generator_internal)
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# can resolve project headers such as #include "phlex/core/...".
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# The _export.hpp headers live in PROJECT_BINARY_DIR/include/phlex.
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# Without CXX_VISIBILITY_PRESET hidden the export macros expand to the default
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# visibility attribute, making every symbol visible — exactly what we want here.
94+
target_include_directories(
95+
${internal}
96+
PUBLIC
97+
"$<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>"
98+
"$<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/include>"
99+
)
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# Propagate compile definitions and options that the public target carries
102+
# (e.g. BOOST_DLL_USE_STD_FS for run_phlex) so the internal build is equivalent.
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get_target_property(defs ${target} COMPILE_DEFINITIONS)
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if(defs)
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target_compile_definitions(${internal} PRIVATE ${defs})
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endif()
107+
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get_target_property(opts ${target} COMPILE_OPTIONS)
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if(opts)
110+
# The _internal library is built with default (interposable) visibility, so
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# -fno-semantic-interposition must not be propagated: that flag is only safe
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# when -fvisibility=hidden bounds the exported-symbol set (PHLEX_HIDE_SYMBOLS=ON
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# on the *public* target), and applying it to fully-visible code violates the
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# safety assumption and would make internal/public benchmarks inaccurate.
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list(FILTER opts EXCLUDE REGEX "^-fno-semantic-interposition$")
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if(opts)
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target_compile_options(${internal} PRIVATE ${opts})
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endif()
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endif()
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endfunction()

‎phlex/CMakeLists.txt‎

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@@ -33,6 +33,8 @@ cet_make_library(
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Boost::json
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phlex::core
3535
)
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phlex_apply_symbol_visibility(phlex_configuration_internal)
37+
phlex_apply_optimizations(phlex_configuration_internal)
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3739
cet_make_library(
3840
LIBRARY_NAME

‎phlex/app/CMakeLists.txt‎

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Original file line numberDiff line numberDiff line change
@@ -5,7 +5,7 @@ add_library(version_obj OBJECT version.cpp)
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# version.cpp is generated into the build directory; clang-tidy cannot find
66
# .clang-tidy by walking the build-dir path, so disable linting for this file.
77
set_target_properties(version_obj PROPERTIES CXX_CLANG_TIDY "" POSITION_INDEPENDENT_CODE TRUE)
8-
target_include_directories(version_obj PRIVATE ${PROJECT_SOURCE_DIR} ${CMAKE_BINARY_DIR}/include)
8+
target_include_directories(version_obj PRIVATE ${PROJECT_SOURCE_DIR} ${PROJECT_BINARY_DIR}/include)
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1010
cet_make_library(
1111
LIBRARY_NAME
@@ -26,10 +26,20 @@ cet_make_library(
2626
)
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install(FILES load_module.hpp run.hpp version.hpp DESTINATION include/phlex/app)
29+
phlex_apply_symbol_visibility(run_phlex)
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phlex_apply_optimizations(run_phlex)
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3032
# We'll use C++17's filesystem instead of Boost's
3133
target_compile_definitions(run_phlex PRIVATE BOOST_DLL_USE_STD_FS)
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phlex_make_internal_library(
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run_phlex
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LIBRARIES
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PUBLIC phlex_core_internal Boost::json Boost::boost
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)
40+
# BOOST_DLL_USE_STD_FS is propagated from run_phlex's COMPILE_DEFINITIONS by
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# phlex_make_internal_library, so no explicit repeat is needed here.
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3343
cet_make_exec(
3444
NAME phlex
3545
SOURCE phlex.cpp

‎phlex/app/load_module.hpp‎

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@@ -1,6 +1,8 @@
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#ifndef PHLEX_APP_LOAD_MODULE_HPP
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#define PHLEX_APP_LOAD_MODULE_HPP
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4+
#include "phlex/run_phlex_export.hpp"
5+
46
#include "phlex/core/fwd.hpp"
57
#include "phlex/driver.hpp"
68

@@ -10,12 +12,17 @@ namespace phlex::experimental {
1012
namespace detail {
1113
// Adjust_config adds the module_label as a parameter, and it checks if the 'py'
1214
// parameter exists, inserting the 'cpp: "pymodule"' configuration if necessary.
13-
boost::json::object adjust_config(std::string const& label, boost::json::object raw_config);
15+
run_phlex_EXPORT boost::json::object adjust_config(std::string const& label,
16+
boost::json::object raw_config);
1417
}
1518

16-
void load_module(framework_graph& g, std::string const& label, boost::json::object config);
17-
void load_source(framework_graph& g, std::string const& label, boost::json::object config);
18-
driver_bundle load_driver(boost::json::object const& config);
19+
run_phlex_EXPORT void load_module(framework_graph& g,
20+
std::string const& label,
21+
boost::json::object config);
22+
run_phlex_EXPORT void load_source(framework_graph& g,
23+
std::string const& label,
24+
boost::json::object config);
25+
run_phlex_EXPORT driver_bundle load_driver(boost::json::object const& config);
1926
}
2027

2128
#endif // PHLEX_APP_LOAD_MODULE_HPP

‎phlex/app/run.hpp‎

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@@ -1,12 +1,14 @@
11
#ifndef PHLEX_APP_RUN_HPP
22
#define PHLEX_APP_RUN_HPP
33

4+
#include "phlex/run_phlex_export.hpp"
5+
46
#include "boost/json.hpp"
57

68
#include <optional>
79

810
namespace phlex::experimental {
9-
void run(boost::json::object const& configurations, int max_parallelism);
11+
run_phlex_EXPORT void run(boost::json::object const& configurations, int max_parallelism);
1012
}
1113

1214
#endif // PHLEX_APP_RUN_HPP

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