Files
esp-idf/components/cxx/CMakeLists.txt
Frantisek Hrbata 94c4fe3d94 fix(cxx): avoid self-referential generator expression in libgcc_cxx
The cxx component re-injects its own archive late on the link line so its
stack-unwind wrappers take precedence over libgcc's (when C++ exceptions
are disabled). It does this through an INTERFACE helper, libgcc_cxx, that
carries `$<TARGET_FILE:${cxx}>`. That helper was linked back into the cxx
target with PUBLIC, which places it in the cxx archive's own
LINK_LIBRARIES, so the cxx target ends up transitively referencing its
own output file.

When CMake computes the cxx target's sources it walks the target's own
link implementation, encounters `$<TARGET_FILE:${cxx}>`, and to resolve the
file it needs the target's link language, which in turn needs its
sources. This loop makes generation fail with:

    The SOURCES of "..." use a generator expression that depends on the
    SOURCES themselves.

CMake only hits this when it reaches the cxx target standalone before the
target has been pulled into a link by a consumer, and whether that
happens depends on the project layout and target evaluation order. That
is why it surfaces only in some projects, while the examples build fine.

Link libgcc_cxx as INTERFACE instead of PUBLIC. A static archive is not
linked, so its private LINK_LIBRARIES are inert; consumers still receive
libgcc_cxx through INTERFACE_LINK_LIBRARIES, so the intended link order is
preserved. Removing the self-reference makes generation independent of
evaluation order.

Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>
2026-08-06 15:31:37 +02:00

104 lines
4.2 KiB
CMake

idf_build_get_property(target IDF_TARGET)
idf_build_get_property(esp_tee_build ESP_TEE_BUILD)
if(${target} STREQUAL "linux")
return() # This component is not necessary on the POSIX/Linux simulator
endif()
set(srcs "cxx_exception_stubs.cpp")
set(priv_requires)
if(NOT esp_tee_build)
list(APPEND srcs "cxx_guards.cpp" "cxx_init.cpp")
# Make sure that pthread is in component list
list(APPEND priv_requires pthread)
endif()
idf_component_register(SRCS ${srcs}
PRIV_REQUIRES ${priv_requires})
if(esp_tee_build OR NOT CONFIG_CXX_EXCEPTIONS)
set(WRAP_FUNCTIONS
__register_frame_info_bases
__register_frame_info
__register_frame
__register_frame_info_table_bases
__register_frame_info_table
__register_frame_table
__deregister_frame_info_bases
__deregister_frame_info
_Unwind_Find_FDE
_Unwind_GetGR
_Unwind_GetCFA
_Unwind_GetIP
_Unwind_GetIPInfo
_Unwind_GetRegionStart
_Unwind_GetDataRelBase
_Unwind_GetTextRelBase
_Unwind_SetIP
_Unwind_SetGR
_Unwind_GetLanguageSpecificData
_Unwind_FindEnclosingFunction
_Unwind_Resume
_Unwind_RaiseException
_Unwind_DeleteException
_Unwind_ForcedUnwind
_Unwind_Resume_or_Rethrow
_Unwind_Backtrace
__cxa_call_unexpected
__gxx_personality_v0
__cxa_throw
__cxa_allocate_exception)
foreach(wrap ${WRAP_FUNCTIONS})
target_link_libraries(${COMPONENT_LIB} INTERFACE "-Wl,--wrap=${wrap}")
endforeach()
endif()
if(CMAKE_C_COMPILER_ID MATCHES "Clang")
# libstdc++ depends on C library, so it should appear later in link order.
# Otherwise we get undefined references for esp-clang toolchain.
target_link_libraries(${COMPONENT_LIB} PUBLIC stdc++ c ${CONFIG_COMPILER_RT_LIB_NAME})
else()
target_link_libraries(${COMPONENT_LIB} PUBLIC stdc++ gcc)
endif()
add_library(stdcpp_deps INTERFACE)
target_link_libraries(${COMPONENT_LIB} PUBLIC stdcpp_deps)
if(NOT esp_tee_build)
target_link_libraries(${COMPONENT_LIB} INTERFACE "-u __cxa_guard_dummy")
target_link_libraries(${COMPONENT_LIB} INTERFACE "-u __cxx_init_dummy")
# Force libpthread to appear later than libstdc++ in link line since libstdc++ depends on libpthread.
# Furthermore, force libcxx to appear later than libgcc because some libgcc unwind code is wrapped, if C++
# exceptions are disabled. libcxx (this component) provides the unwind code wrappers.
# This is to prevent linking of libgcc's unwind code which considerably increases the binary size.
# Also force esp_libc to appear later than libstdc++ in link line since libstdc++ depends on
# some functions in esp_libc, e.g. getentropy().
idf_component_get_property(pthread pthread COMPONENT_LIB)
idf_component_get_property(esp_libc esp_libc COMPONENT_LIB)
if(CMAKE_C_COMPILER_ID MATCHES "Clang")
target_link_libraries(stdcpp_deps INTERFACE stdc++ c $<TARGET_FILE:${pthread}> $<TARGET_FILE:${esp_libc}>)
else()
target_link_libraries(stdcpp_deps INTERFACE stdc++ $<TARGET_FILE:${pthread}> $<TARGET_FILE:${esp_libc}>)
endif()
endif()
idf_component_get_property(cxx cxx COMPONENT_LIB)
add_library(libgcc_cxx INTERFACE)
target_link_libraries(libgcc_cxx INTERFACE ${CONFIG_COMPILER_RT_LIB_NAME} $<TARGET_FILE:${cxx}>)
# Link as INTERFACE, not PUBLIC: libgcc_cxx references $<TARGET_FILE:${cxx}>, so adding it to the
# cxx archive's own LINK_LIBRARIES would make the target depend on its own TARGET_FILE. CMake then
# needs the link language (hence SOURCES) to resolve that TARGET_FILE, which is a self-reference and
# fails generation with "The SOURCES of '...' use a generator expression that depends on the SOURCES
# themselves" whenever the cxx target is not itself link-consumed (e.g. cmakev2, IDFGH-16748). A
# static archive isn't linked, so its private link libraries are inert; consumers still get
# libgcc_cxx through INTERFACE_LINK_LIBRARIES, preserving link order.
target_link_libraries(${COMPONENT_LIB} INTERFACE libgcc_cxx)
if(NOT CONFIG_COMPILER_CXX_EXCEPTIONS)
target_link_libraries(${COMPONENT_LIB} INTERFACE "-u __cxx_fatal_exception")
endif()