缺少LLVM编译器-rt的libclang_rt.san-x86_64.a文件

Question

我刚刚构建了LLVM/Clang compiler-rt并尝试了该-fsanitize选项.但奇怪的是链接失败,因为它无法找到libclang_rt.san-x86_64.a.

/usr/bin/ld: cannot find /home/hongxu/RESEARCH/llvm-git/obj/bin/../lib/clang/3.7.0/lib/linux/libclang_rt.san-x86_64.a: No such file or directory
clang-3.7: error: linker command failed with exit code 1 (use -v to see invocation)

当我进入目录时/home/hongxu/RESEARCH/llvm-git/obj/bin/../lib/clang/3.7.0/lib/linux/,我发现还有其他库文件

# AddressSanitizer
libclang_rt.asan_cxx-x86_64.a
libclang_rt.asan-preinit-x86_64.a
libclang_rt.asan-x86_64.a
# DataFlowSanitizer
libclang_rt.dfsan-libc-x86_64.a
libclang_rt.dfsan-x86_64.a
# LeakSanitizer
libclang_rt.lsan-x86_64.a
# MemorySanitizer
libclang_rt.msan-x86_64.a
# ThreadSanitizer
libclang_rt.tsan-x86_64.a
# UndefinedBehaviorSanitizer
libclang_rt.ubsan_cxx-x86_64.a
libclang_rt.ubsan_standalone_cxx-x86_64.a
libclang_rt.ubsan_standalone-x86_64.a
libclang_rt.ubsan-x86_64.a

我可以根据compiler-rt页面从名称中猜出它们的功能.

但是什么libclang_rt.san-x86_64.a呢？我怎么能得到它？

Answer 1

但奇怪的是链接失败了，因为它找不到 libclang_rt.san-x86_64.a。

是的，make install不安装一些需要的东西。其他时候，它会将它们安装在非标准位置。

它没有安装的其他东西包括asan_symbolize.py，它用于符号化来自 Address Sanitizer (ASan) 的转储。

但什么是 libclang_rt.san-x86_64.a？我怎样才能得到它？

它是消毒剂库之一。您可能拥有它，只是您没有意识到它，因为它位于非标准位置。例如，在我的系统上（我自己构建 LLVM/Clang）：

$ find /usr -name libclang_rt.san-x86_64.a 2>/dev/null 
/usr/local/lib/clang/3.5.0/lib/linux/libclang_rt.san-x86_64.a

因此，您需要做的是使用LD_LIBRARY_PATH(Linux) 或DYLD_LIBRARY_PATH(OS X) 来确保编译器驱动程序可以找到它。您永远不必手动添加各种消毒剂库 - 编译器驱动程序应该始终为您添加它们。

为了完整起见，Clang 3.4/usr/local/lib/clang/3.4/lib/linux/在 Linux 上安装了 sanitizers 库；和 Clang 3.3/usr/local/lib/clang/3.3/lib/darwin/在 OS X 上安装它们。

您实际上可以更改源代码中的搜索目录，编译器驱动程序会自动选取它们。我想我必须更改实际来源，因为我找不到添加位置的配置选项，例如/usr/local/lib/clang/<version>/lib/linux/. 看看tools/clang/lib/Frontend/InitHeaderSearch.cpp和朋友。这就是路径之类的.../include/c++/4.2.1来源。

顺便说一下，这里是如何使用 Address Sanitizer 和asan_symbolize.py. 首先，运行2to3并asan_symbolize.py修复 Python 人员破坏的与基本 I/O 相关的问题：

$ find Clang-3.5/ -name asan_symbolize.py
Clang-3.5/llvm/projects/compiler-rt/lib/asan/scripts/asan_symbolize.py
2to3 -w Clang-3.5/llvm/projects/compiler-rt/lib/asan/scripts/asan_symbolize.py

echo "" | Clang-3.5/llvm/projects/compiler-rt/lib/asan/scripts/asan_symbolize.py
# Fix errors 2to3 missed

然后，将其复制到众所周知的位置（或将其放在路径上）：

sudo cp Clang-3.5/llvm/projects/compiler-rt/lib/asan/scripts/asan_symbolize.py /usr/local/bin

然后，对于您的项目：

export CPPFLAGS="-fsanitze=undefined -fsanitize=address"
export CFLAGS="-fsanitze=undefined -fsanitize=address"
export CXXFLAGS="-fsanitze=undefined -fsanitize=address -fno-sanitize=vptr"
export CC=/usr/local/bin/clang
export CXX=/usr/local/bin/clang++
export LD_LIBRARY_PATH=/usr/local/lib/clang/3.5.0/lib/linux

./configure
make
make check 2>&1 | asan_symbolize.py

CPPFLAGS实际上对于 Autotools 项目非常重要。否则，你会得到可怕的C 编译器无法创建可执行文件的错误。

当您遇到 ASan 错误时，您将看到类似于：

make test 2>&1 | asan_symbolize.py
...

/usr/local/bin/clang -fsanitize=address -Xlinker -export-dynamic
    -o python Modules/python.o libpython3.3m.a -ldl -lutil
    /usr/local/ssl/lib/libssl.a /usr/local/ssl/lib/libcrypto.a -lm
./python -E -S -m sysconfig --generate-posix-vars
=================================================================
==24064==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x619000004020 at pc 0x4ed4b2 bp 0x7fff80fff010 sp 0x7fff80fff008
READ of size 4 at 0x619000004020 thread T0
  #0 0x4ed4b1 in PyObject_Free Python-3.3.5/./Objects/obmalloc.c:987
  #1 0x7a2141 in code_dealloc Python-3.3.5/./Objects/codeobject.c:359
  #2 0x620c00 in PyImport_ImportFrozenModuleObject
       Python-3.3.5/./Python/import.c:1098
  #3 0x620d5c in PyImport_ImportFrozenModule
       Python-3.3.5/./Python/import.c:1114
  #4 0x63fd07 in import_init Python-3.3.5/./Python/pythonrun.c:206
  #5 0x63f636 in _Py_InitializeEx_Private
       Python-3.3.5/./Python/pythonrun.c:369
  #6 0x681d77 in Py_Main Python-3.3.5/./Modules/main.c:648
  #7 0x4e6894 in main Python-3.3.5/././Modules/python.c:62
  #8 0x2abf9a525eac in __libc_start_main
       /home/aurel32/eglibc/eglibc-2.13/csu/libc-start.c:244
  #9 0x4e664c in _start (Python-3.3.5/./python+0x4e664c)

AddressSanitizer can not describe address in more detail (wild
memory access suspected).
SUMMARY: AddressSanitizer: heap-buffer-overflow
  Python-3.3.5/./Objects/obmalloc.c:987 PyObject_Free
Shadow bytes around the buggy address:
  0x0c327fff87b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff87c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff87d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff87e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff87f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c327fff8800: fa fa fa fa[fa]fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff8810: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff8820: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff8830: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff8840: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff8850: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:     fa
  Heap right redzone:    fb
  Freed heap region:     fd
  Stack left redzone:    f1
  Stack mid redzone:     f2
  Stack right redzone:   f3
  Stack partial redzone: f4
  Stack after return:    f5
  Stack use after scope: f8
  Global redzone:        f9
  Global init order:     f6
  Poisoned by user:      f7
  ASan internal:         fe
==24064==ABORTING
make: *** [pybuilddir.txt] Error 1

在 Python 的Dynamic Analysis with Clang 中有更完整的 LLVM/Clang 构建过程和使用 santizer 的文章。我前段时间写的，所以版本和配方都是陈旧的。但是概念是一样的。

Answer 2

感谢@jww 的回答；但我的问题不同。

我收到了来自 llvmdev 邮件列表的回复（请参阅线程），他们说：

libclang_rt.san 现在已经消失了。新的编译器-rt 版本不包含此库，并且新的 Clang 不使用它。

我无法编译，因为我在编译之前没有同步其他 llvm 项目（我只将编译器-rt 放在 llvm/projects 目录中并从 llvm 构建根目录构建）。

解决方案很简单：

尝试从头开始构建（删除构建目录，将所有 llvm 子项目同步到同一版本，再次构建）。