[cfe-dev] Interesting behaviour with UBSAN+libc++

[İsmail Dönmez]

I got some very simple code, dumbed down from a larger one:

[~]> cat wc.cpp
#include <iostream>

int wc() {
    return 0;
}

int main()
{
    std::cout << wc() << std::endl;
}

[~]> /opt/clang/bin/clang++ -stdlib=libc++ -fsanitize=undefined wc.cpp
[~]> ./a.out
/opt/clang/bin/../include/c++/v1/ostream:1034:14: runtime error: member
call on address 0x000000ef9858 which does not point to an object of type
'std::__1::basic_ios<char>'
0x000000ef9850: note: object is base class subobject at offset 8 within
object of type 'std::__1::basic_ostream<char, std::__1::char_traits<char> >'
 00 00 00 00  40 a3 b9 c6 b1 7f 00 00  68 a3 b9 c6 b1 7f 00 00  02 10 00 00
00 00 00 00  06 00 00 00
              ^                        ~~~~~~~~~~~~~~~~~~~~~~~
                                       vptr for '<unknown>' base class of
'std::__1::basic_ostream<char, std::__1::char_traits<char> >'
/opt/clang/bin/../include/c++/v1/ios:734:41: runtime error: member call on
address 0x000000ef9858 which does not point to an object of type
'std::__1::ios_base'
0x000000ef9850: note: object is base class subobject at offset 8 within
object of type 'std::__1::basic_ostream<char, std::__1::char_traits<char> >'
 00 00 00 00  40 a3 b9 c6 b1 7f 00 00  68 a3 b9 c6 b1 7f 00 00  02 10 00 00
00 00 00 00  06 00 00 00
              ^                        ~~~~~~~~~~~~~~~~~~~~~~~
                                       vptr for '<unknown>' base class of
'std::__1::basic_ostream<char, std::__1::char_traits<char> >'
0


Works fine if I link to libstdc++. clang is r223341.
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