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

Eric Fiselier eric at efcs.ca
Thu Dec 4 13:05:43 PST 2014


Did you compile libc++ with UBSAN?

/Eric

On Thu, Dec 4, 2014 at 6:21 AM, İsmail Dönmez <ismail at donmez.ws> wrote:
> 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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