From 499d087c91141834bc41a282a592ba1d61f7b2c8 Mon Sep 17 00:00:00 2001 From: Ivan Grokhotkov Date: Thu, 6 Jun 2019 16:53:26 +0800 Subject: [PATCH] C++: add provisions for optional RTTI support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Ref. https://github.com/espressif/esp-idf/issues/1684 This change allows RTTI to be enabled in menuconfig. For full RTTI support, libstdc++.a in the toolchain should be built without -fno-rtti, as it is done now. Generally if libstdc++.a is built with RTTI, applications which do not use RTTI (and build with -fno-rtti) could still include typeinfo structures referenced from STL classes’ vtables. This change works around this, by moving all typeinfo structures from libstdc++.a into a non-loadable section, placed into a non-existent memory region starting at address 0. This can be done because when the application is compiled with -fno-rtti, typeinfo structures are not used at run time. This way, typeinfo structures do not contribute to the application binary size. If the application is build with RTTI support, typeinfo structures are linked into the application .rodata section as usual. Note that this commit does not actually enable RTTI support. The respective Kconfig option is hidden, and will be made visible when the toolchain is updated. --- CMakeLists.txt | 6 ++++++ Kconfig | 9 +++++++++ components/esp32/CMakeLists.txt | 5 +++++ components/esp32/component.mk | 21 +++++++++++++-------- components/esp32/ld/esp32.discard-rtti.ld | 11 +++++++++++ components/esp32/ld/esp32.ld | 5 +++++ make/project.mk | 7 ++++++- tools/cmake/build.cmake | 3 +-- 8 files changed, 56 insertions(+), 11 deletions(-) create mode 100644 components/esp32/ld/esp32.discard-rtti.ld diff --git a/CMakeLists.txt b/CMakeLists.txt index 4dae14c8c..55c9109f9 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -27,6 +27,12 @@ else() list(APPEND cxx_compile_options "-fno-exceptions") endif() +if(CONFIG_COMPILER_CXX_RTTI) + list(APPEND cxx_compile_options "-frtti") +else() + list(APPEND cxx_compile_options "-fno-rtti") +endif() + if(CONFIG_COMPILER_DISABLE_GCC8_WARNINGS) list(APPEND compile_options "-Wno-parentheses" "-Wno-sizeof-pointer-memaccess" diff --git a/Kconfig b/Kconfig index 92c76c38d..815f87d07 100644 --- a/Kconfig +++ b/Kconfig @@ -237,6 +237,15 @@ mainmenu "Espressif IoT Development Framework Configuration" Size (in bytes) of the emergency memory pool for C++ exceptions. This pool will be used to allocate memory for thrown exceptions when there is not enough memory on the heap. + config COMPILER_CXX_RTTI + # Invisible option, until the toolchain with RTTI support is released. + # Use prompt "Enable C++ run-time type info (RTTI)" when updating. + bool + help + Enabling this option compiles all C++ files with RTTI support enabled. + This increases binary size (typically by tens of kB) but allows using + dynamic_cast conversion and typeid operator. + choice COMPILER_STACK_CHECK_MODE prompt "Stack smashing protection mode" default COMPILER_STACK_CHECK_MODE_NONE diff --git a/components/esp32/CMakeLists.txt b/components/esp32/CMakeLists.txt index 7d9ad3872..70a380593 100644 --- a/components/esp32/CMakeLists.txt +++ b/components/esp32/CMakeLists.txt @@ -56,6 +56,11 @@ else() target_linker_script(${COMPONENT_LIB} INTERFACE "ld/esp32.extram.bss.ld") endif() + if(NOT CONFIG_COMPILER_CXX_RTTI) + # This has to be linked before esp32.project.ld + target_linker_script(${COMPONENT_LIB} INTERFACE "ld/esp32.discard-rtti.ld") + endif() + # Process the template file through the linker script generation mechanism, and use the output for linking the # final binary target_linker_script(${COMPONENT_LIB} INTERFACE "${CMAKE_CURRENT_LIST_DIR}/ld/esp32.project.ld.in" diff --git a/components/esp32/component.mk b/components/esp32/component.mk index 8f999b26d..836f242e2 100644 --- a/components/esp32/component.mk +++ b/components/esp32/component.mk @@ -5,18 +5,23 @@ COMPONENT_SRCDIRS := . ifdef CONFIG_SPIRAM_ALLOW_BSS_SEG_EXTERNAL_MEMORY - # This linker script must come before esp32.project.ld - LINKER_SCRIPTS += esp32.extram.bss.ld + # This linker script must come before esp32.project.ld + LINKER_SCRIPTS += esp32.extram.bss.ld endif -#Linker scripts used to link the final application. -#Warning: These linker scripts are only used when the normal app is compiled; the bootloader -#specifies its own scripts. +ifndef CONFIG_COMPILER_CXX_RTTI + # This linker script must come before esp32.project.ld + LINKER_SCRIPTS += esp32.discard-rtti.ld +endif + +# Linker scripts used to link the final application. +# Warning: These linker scripts are only used when the normal app is compiled; the bootloader +# specifies its own scripts. LINKER_SCRIPTS += $(COMPONENT_BUILD_DIR)/esp32.project.ld esp32.peripherals.ld -#ld_include_panic_highint_hdl is added as an undefined symbol because otherwise the -#linker will ignore panic_highint_hdl.S as it has no other files depending on any -#symbols in it. +# ld_include_panic_highint_hdl is added as an undefined symbol because otherwise the +# linker will ignore panic_highint_hdl.S as it has no other files depending on any +# symbols in it. COMPONENT_ADD_LDFLAGS += -L $(COMPONENT_PATH)/ld \ -T esp32_out.ld \ -u ld_include_panic_highint_hdl \ diff --git a/components/esp32/ld/esp32.discard-rtti.ld b/components/esp32/ld/esp32.discard-rtti.ld new file mode 100644 index 000000000..f9fdff994 --- /dev/null +++ b/components/esp32/ld/esp32.discard-rtti.ld @@ -0,0 +1,11 @@ +/* This is only included if CONFIG_COMPILER_CXX_RTTI is not set, to + * move RTTI sections of libstdc++ to an unused non-loadable memory region. + */ + +SECTIONS +{ + .rodata.discard-rtti (NOLOAD): + { + *libstdc++.a:(.rodata._ZTI* .rodata._ZTS*) + } > discard_seg +} diff --git a/components/esp32/ld/esp32.ld b/components/esp32/ld/esp32.ld index 0400fc2ab..cb0f14437 100644 --- a/components/esp32/ld/esp32.ld +++ b/components/esp32/ld/esp32.ld @@ -98,6 +98,11 @@ MEMORY /* external memory ,including data and text */ extern_ram_seg(RWX) : org = 0x3F800000, len = 0x400000 + + /* This is not a memory range which can really be accessed; we use it as a "bitbucket" + where non-loadable sections, which aren't used at run time, can be discarded. + */ + discard_seg (R) : org = 0x00000000, len = 0x10000000 } #if defined(CONFIG_ESP32_USE_FIXED_STATIC_RAM_SIZE) diff --git a/make/project.mk b/make/project.mk index a8ec59f40..61e80ac06 100644 --- a/make/project.mk +++ b/make/project.mk @@ -468,7 +468,6 @@ CXXFLAGS ?= EXTRA_CXXFLAGS ?= CXXFLAGS := $(strip \ -std=gnu++11 \ - -fno-rtti \ $(OPTIMIZATION_FLAGS) $(DEBUG_FLAGS) \ $(COMMON_FLAGS) \ $(COMMON_WARNING_FLAGS) \ @@ -481,6 +480,12 @@ else CXXFLAGS += -fno-exceptions endif +ifdef CONFIG_COMPILER_CXX_RTTI +CXXFLAGS += -frtti +else +CXXFLAGS += -fno-rtti +endif + ARFLAGS := cru export CFLAGS CPPFLAGS CXXFLAGS ARFLAGS diff --git a/tools/cmake/build.cmake b/tools/cmake/build.cmake index f495ed8fa..c3bbdeaff 100644 --- a/tools/cmake/build.cmake +++ b/tools/cmake/build.cmake @@ -114,8 +114,7 @@ function(__build_set_default_build_specifications) list(APPEND c_compile_options "-std=gnu99" "-Wno-old-style-declaration") - list(APPEND cxx_compile_options "-std=gnu++11" - "-fno-rtti") + list(APPEND cxx_compile_options "-std=gnu++11") idf_build_set_property(COMPILE_DEFINITIONS "${compile_definitions}" APPEND) idf_build_set_property(COMPILE_OPTIONS "${compile_options}" APPEND)