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A C++ module with a static object does not link. GCC registers each such object's destructor with __cxa_atexit(dtor, obj, &__dso_handle), and __dso_handle comes from crtbegin, which a module does not link: hello++3.cxx:119: undefined reference to `__dso_handle' It is reachable today with CONFIG_PIC, where a module is linked as an executable and the symbol has to resolve. Without it the link is relocatable, the symbol stays undefined and nothing complains until something makes it resolve. -fno-use-cxa-atexit registers the destructors with atexit() instead, which puts them in .fini_array. That is also where libelf_uninit() looks for them when the module is unloaded, so the flag that makes the link work is also the flag that makes the destructors run. The option goes wherever CXXELFFLAGS is defined, which is the architecture Toolchain.defs and the boards that reassign it. The toolchains that are not GCC or Clang are left alone: ceva, tricore, z16 and the z80 family. The CMake build sets it once, next to where the architecture elf.cmake is included. A generator expression keeps it off the C compiles, because the option is valid for C++ alone and GCC warns about it otherwise, and the compiler id gates it so that a toolchain which is neither GCC nor Clang does not see it. It cannot go in the toolchain file itself: CMake reads that file again inside try_compile, in a project that has not included the NuttX extensions, so the call is an unknown command there. Reproduced with apps/examples/elf on mps3-an547:picostest with CONFIG_PIC enabled: hello++3 fails to link before and links after. Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com> Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
71 lines
2.7 KiB
Text
71 lines
2.7 KiB
Text
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# boards/risc-v/esp32c6/esp32c6-devkitc/scripts/Make.defs
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#
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# SPDX-License-Identifier: Apache-2.0
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#
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# Licensed to the Apache Software Foundation (ASF) under one or more
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# contributor license agreements. See the NOTICE file distributed with
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# this work for additional information regarding copyright ownership. The
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# ASF licenses this file to you under the Apache License, Version 2.0 (the
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# "License"); you may not use this file except in compliance with the
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# License. You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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#
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###########################################################################
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include $(TOPDIR)/.config
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include $(TOPDIR)/tools/Config.mk
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include $(TOPDIR)/tools/espressif/Config.mk
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include $(TOPDIR)/arch/risc-v/src/common/Toolchain.defs
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# Remove quotes from CONFIG_ESPRESSIF_CHIP_SERIES configuration
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CHIP_SERIES = $(patsubst "%",%,$(CONFIG_ESPRESSIF_CHIP_SERIES))
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# Pick the linker scripts from the board level if they exist, if not
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# pick the common linker scripts.
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ARCHSCRIPT += $(BOARD_COMMON_DIR)/scripts/$(CHIP_SERIES)_aliases.ld
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ARCHSCRIPT += $(call FINDSCRIPT,$(CHIP_SERIES)_flat_memory.ld)
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ifeq ($(CONFIG_ESPRESSIF_SIMPLE_BOOT),y)
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ARCHSCRIPT += $(call FINDSCRIPT,$(CHIP_SERIES)_sections.ld)
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else ifeq ($(CONFIG_ESPRESSIF_BOOTLOADER_MCUBOOT),y)
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ARCHSCRIPT += $(call FINDSCRIPT,$(CHIP_SERIES)_sections.ld)
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else
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ARCHSCRIPT += $(call FINDSCRIPT,$(CHIP_SERIES)_legacy_sections.ld)
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endif
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CFLAGS := $(ARCHCFLAGS) $(ARCHOPTIMIZATION) $(ARCHCPUFLAGS) $(ARCHINCLUDES) $(ARCHDEFINES) $(EXTRAFLAGS) -Werror=return-type
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CPICFLAGS = $(ARCHPICFLAGS) $(CFLAGS)
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CXXFLAGS := $(ARCHCXXFLAGS) $(ARCHOPTIMIZATION) $(ARCHCPUFLAGS) $(ARCHXXINCLUDES) $(ARCHDEFINES) $(EXTRAFLAGS)
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CXXPICFLAGS = $(ARCHPICFLAGS) $(CXXFLAGS)
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CPPFLAGS := $(ARCHINCLUDES) $(ARCHDEFINES) $(EXTRAFLAGS)
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AFLAGS := $(CFLAGS) -D__ASSEMBLY__
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# Loadable module definitions
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CMODULEFLAGS = $(CFLAGS)
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LDMODULEFLAGS = -melf32lriscv -r -e module_initialize
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LDMODULEFLAGS += -T $(call CONVERT_PATH,$(TOPDIR)/libs/libc/elf/gnu-elf.ld)
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# ELF module definitions
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CELFFLAGS = $(CFLAGS)
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CXXELFFLAGS = $(CXXFLAGS)
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# __dso_handle comes from crtbegin, which a module does not link
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CXXELFFLAGS += -fno-use-cxa-atexit
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LDELFFLAGS = -melf32lriscv -r -e main
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LDELFFLAGS += -T $(call CONVERT_PATH,$(TOPDIR)/binfmt/elf/gnu-elf.ld)
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