casaroli commented on code in PR #19940:
URL: https://github.com/apache/nuttx/pull/19940#discussion_r3916135462
##########
arch/arm/src/cmake/elf.cmake:
##########
@@ -27,17 +27,54 @@ nuttx_mod_compile_options(-fvisibility=hidden -mlong-calls)
nuttx_elf_compile_options_ifdef(CONFIG_UNWINDER_ARM -fno-unwind-tables
-fno-asynchronous-unwind-tables)
-# An ELF module needs r9 as its PIC base, so it must not also have the register
-# fixed: GCC rejects that pair with "unable to use 'r9' for PIC register".
This
-# mirrors CELFFLAGS in common/Toolchain.defs, which filters --fixed-r9 back out
-# of the inherited CFLAGS for the same reason.
+# -fno-use-cxa-atexit, because the default registers each static object's
+# destructor with __cxa_atexit(dtor, obj, &__dso_handle), and __dso_handle
comes
+# from crtbegin, which a module does not link. Turning it off also puts the
+# destructors in .fini_array, which is where the loader looks for them when the
+# module is unloaded. This mirrors CXXELFFLAGS in common/Toolchain.defs.
-nuttx_elf_compile_options_ifdef(CONFIG_PIC -mpic-register=r9)
+nuttx_elf_compile_options(-fno-use-cxa-atexit)
-nuttx_elf_link_options_ifdef(
- CONFIG_PIC --unresolved-symbols=ignore-in-object-files --emit-relocs)
+if(CONFIG_FDPIC)
-nuttx_elf_link_options_ifdef(CONFIG_BINFMT_ELF_RELOCATABLE -r)
+ # An FDPIC module is a shared object whose two segments the loader places
+ # independently. The stock compiler emits correct FDPIC objects for both C
+ # and C++, so only the link needs the arm-uclinuxfdpiceabi linker: the stock
+ # one carries the armelf emulation alone and would turn every import into a
+ # jump slot where the ABI wants a function descriptor.
+
+ if(NOT FDPIC_CROSSDEV)
+ set(FDPIC_CROSSDEV arm-uclinuxfdpiceabi-)
+ endif()
+
+ set(CMAKE_ELF_LD
+ "${FDPIC_CROSSDEV}ld"
+ CACHE INTERNAL "Linker for FDPIC modules")
+
+ nuttx_elf_compile_options(-mfdpic -fPIC -Wa,--noexecstack)
+
+ nuttx_elf_link_options(-m armelf_linux_fdpiceabi -shared -z now)
+
+else()
+
+ # An ELF module needs r9 as its PIC base, so it must not also have the
+ # register fixed: GCC rejects that pair with "unable to use 'r9' for PIC
+ # register". This mirrors CELFFLAGS in common/Toolchain.defs, which filters
+ # --fixed-r9 back out of the inherited CFLAGS for the same reason.
+
+ nuttx_elf_compile_options_ifdef(CONFIG_PIC -mpic-register=r9)
+
+ nuttx_elf_link_options_ifdef(
+ CONFIG_PIC --unresolved-symbols=ignore-in-object-files --emit-relocs)
+
+endif()
+
+# Not with CONFIG_PIC: there the module is linked as an executable, which is
+# what common/Toolchain.defs does too.
+
+if(CONFIG_BINFMT_ELF_RELOCATABLE AND NOT CONFIG_PIC)
Review Comment:
to match the make side. in **Toolchain.defs** the `-r` sits in the `else` of
`ifeq ($(CONFIG_PIC),y)`, and `BINFMT_ELF_RELOCATABLE`/`BINFMT_ELF_EXECUTABLE`
are a two way choice, so this is the same condition. without it a PIC build
gets `--emit-relocs` and `-r` at once.
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