使用clang编译时无法查看std :: string [英] Cannot view std::string when compiled with clang
问题描述
g ++（GCC）5.2.0
g++ (GCC) 5.2.0
clang版本3.7.1（标签/ RELEASE_371 / final）
clang version 3.7.1 (tags/RELEASE_371/final)
GNU gdb（GDB）7.12
GNU gdb (GDB) 7.12
由于某种原因，用clang编译时，Gdb无法找到std :: string的定义。我已经自定义编译并构建了gcc和clang，因为Centos 6.5随附了较旧的gcc版本。
Gdb is unable to locate the definition of std::string when compiled with clang for some reason. I have custom compiled and build gcc and clang as Centos 6.5 comes with older version of gcc.
示例代码
#include <string>
int main()
{
std::string s("This is a string");
return 0;
}
使用g ++编译并调试-效果很好
Compile with g++ and debug - works just fine
[~]$ g++ -ggdb3 -std=c++14 stl.cpp
[~]$ gdb a.out
GNU gdb (GDB) 7.12
Reading symbols from a.out...done.
(gdb) break main
Breakpoint 1 at 0x400841: file stl.cpp, line 5.
(gdb) r
Starting program: /home/vagrant/a.out
Breakpoint 1, main () at stl.cpp:5
5 std::string s("This is a string");
(gdb) n
7 return 0;
(gdb) p s
$1 = {static npos = <optimized out>,
_M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0x612c20 "This is a string"}, _M_string_length = 16, {
_M_local_buf = "\020\000\000\000\000\000\000\000\300\b@\000\000\000\000", _M_allocated_capacity = 16}}
(gdb)
检查它是否与我的libstdc ++的rpm构建版本链接，而不是系统链接
Check that it is linking with my rpm build version of libstdc++ and not system
[~]$ ldd a.out
linux-vdso.so.1 => (0x00007ffd709e0000)
libstdc++.so.6 => /opt/spotx-gcc/lib64/libstdc++.so.6 (0x00007f29318fa000)
libm.so.6 => /lib64/libm.so.6 (0x00007f2931676000)
libgcc_s.so.1 => /opt/spotx-gcc/lib64/libgcc_s.so.1 (0x00007f293145f000)
libc.so.6 => /lib64/libc.so.6 (0x00007f29310cb000)
/lib64/ld-linux-x86-64.so.2 (0x00007f2931c93000)
[~]$ objdump -T -C a.out
a.out: file format elf64-x86-64
DYNAMIC SYMBOL TABLE:
0000000000000000 w D *UND* 0000000000000000 __gmon_start__
0000000000000000 w D *UND* 0000000000000000 _Jv_RegisterClasses
0000000000000000 DF *UND* 0000000000000000 GLIBC_2.2.5 __libc_start_main
0000000000000000 w D *UND* 0000000000000000 _ITM_deregisterTMCloneTable
0000000000000000 w D *UND* 0000000000000000 _ITM_registerTMCloneTable
0000000000000000 DF *UND* 0000000000000000 GLIBCXX_3.4.21 std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()
0000000000000000 DF *UND* 0000000000000000 GLIBCXX_3.4 std::allocator<char>::~allocator()
0000000000000000 DF *UND* 0000000000000000 GLIBCXX_3.4.21 std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&)
0000000000000000 DF *UND* 0000000000000000 GLIBCXX_3.4 std::allocator<char>::allocator()
0000000000000000 DF *UND* 0000000000000000 GCC_3.0 _Unwind_Resume
0000000000400700 DF *UND* 0000000000000000 CXXABI_1.3 __gxx_personality_v0
如果我用clang尝试相同的话，现在看起来一切都很好
All looks good now if I try the same with clang
[~]$ clang++ -std=c++14 -g stl.cpp
[~]$ gdb a.out
GNU gdb (GDB) 7.12
Reading symbols from a.out...done.
(gdb) break main
Breakpoint 1 at 0x400853: file stl.cpp, line 5.
(gdb) r
Starting program: /home/vagrant/a.out
Breakpoint 1, main () at stl.cpp:5
5 std::string s("This is a string");
(gdb) n
7 return 0;
(gdb) p s
$1 = <incomplete type>
(gdb)
现在我得到的类型不完整-但使用的是相同的库
Now I get an incomplete type - but the same libraries are being used
[~]$ ldd a.out
linux-vdso.so.1 => (0x00007fff5352d000)
libstdc++.so.6 => /opt/spotx-gcc/lib64/libstdc++.so.6 (0x00007f76b4023000)
libm.so.6 => /lib64/libm.so.6 (0x00007f76b3d9f000)
libgcc_s.so.1 => /opt/spotx-gcc/lib64/libgcc_s.so.1 (0x00007f76b3b88000)
libc.so.6 => /lib64/libc.so.6 (0x00007f76b37f4000)
/lib64/ld-linux-x86-64.so.2 (0x00007f76b43bc000)
[~]$ objdump -T -C a.out
a.out: file format elf64-x86-64
DYNAMIC SYMBOL TABLE:
0000000000000000 w D *UND* 0000000000000000 __gmon_start__
0000000000000000 w D *UND* 0000000000000000 _Jv_RegisterClasses
0000000000000000 DF *UND* 0000000000000000 GLIBC_2.2.5 __libc_start_main
0000000000000000 w D *UND* 0000000000000000 _ITM_deregisterTMCloneTable
0000000000000000 w D *UND* 0000000000000000 _ITM_registerTMCloneTable
0000000000000000 DF *UND* 0000000000000000 GLIBCXX_3.4.21 std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()
0000000000000000 DF *UND* 0000000000000000 GLIBCXX_3.4 std::allocator<char>::~allocator()
0000000000000000 DF *UND* 0000000000000000 GLIBCXX_3.4.21 std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&)
0000000000000000 DF *UND* 0000000000000000 GLIBCXX_3.4 std::allocator<char>::allocator()
0000000000000000 DF *UND* 0000000000000000 GCC_3.0 _Unwind_Resume
0000000000400700 DF *UND* 0000000000000000 CXXABI_1.3 __gxx_personality_v0
有人对我在哪里看或我错过的东西有任何建议吗？编译它们时，两个编译器都被引导了-一切似乎都很好-使用clang时，似乎只是未定义std :: string。
Does anyone have any advice on where to look or something that I've missed. Both compilers are bootstrapped when building them - everything seems fine - it just appears to be std::string is not defined when using clang.
推荐答案
如ks1322所述，这是因为clang决定不为libstc ++发出调试信息。
As ks1322 mentioned, this is because clang has decided not to emit debug information for libstc++.
您可以通过提供以下标志来强制clang这样做：
-D_GLIBCXX_DEBUG
You can force clang to do so by providing the following flag:
-D_GLIBCXX_DEBUG
我只会为调试版本提供标志，但是如果debug是默认设置，并且发布版本是一个特殊的目标，您应该将其删除：
I would only provide the flag for debug builds, but if debug is the default and release builds are a special target you should remove it:
release: CXXFLAGS := $(filter-out -D_GLIBCXX_DEBUG,$(CXXFLAGS)) -O2
这为我解决了相同的问题。
This has fixed the same problem for me.
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