1a4b9b6f73
On ELF platforms, when there is no global variable, COMDAT asan.module_ctor is created with no `__asan_register_elf_globals` calls. If this COMDAT is the prevailing copy selected by the linker, the linkage unit will have no `__asan_register_elf_globals` call: the redzone will not be poisoned and ODR violation checker will not work (#67677). This behavior is benign for -fno-sanitize-address-globals-dead-stripping because asan.module_ctor functions that call `__asan_register_globals` (`InstrumentGlobalsWithMetadataArray`) do not use COMDAT. To fix #67677: * Use COMDAT for -fsanitize-address-globals-dead-stripping on ELF platforms. * Call `__asan_register_elf_globals` even if there is no global variable. Alternatively, when there is no global variable, asan.module_ctor is not COMDAT and does not call `__asan_register_elf_globals`. However, the asan.module_ctor function cannot be eliminated by the linker. Tested the following script. Only ELF -fsanitize-address-globals-dead-stripping has changed behaviors. ``` echo > a.cc # no global variable, empty uniqueModuleId echo 'void f() {}' > b.cc # with global variable, with uniqueModuleId echo 'int g;' > c.cc # with global variable for t in x86_64-linux-gnu arm64-apple-macosx x86_64-windows-msvc; do for gc in -f{,no-}sanitize-address-globals-dead-stripping; do for f in a.cc b.cc c.cc; do echo /tmp/Rel/bin/clang -S --target=$t -fsanitize=address $gc $f -o - /tmp/Rel/bin/clang -S --target=$t -fsanitize=address $gc $f -o - | sed -n '/asan.module_ctor/,/ret/p' done done done ```
The LLVM Compiler Infrastructure ================================ This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. Please see the documentation provided in docs/ for further assistance with LLVM, and in particular docs/GettingStarted.rst for getting started with LLVM and docs/README.txt for an overview of LLVM's documentation setup. If you are writing a package for LLVM, see docs/Packaging.rst for our suggestions.