https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80963
Bug ID: 80963
Summary: UBSAN false positive with visibility=hidden
Product: gcc
Version: 7.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: jengelh at inai dot de
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at
gcc dot gnu.org
Target Milestone: ---
$ cat lib.h
struct Archive {
virtual void foo() = 0;
};
__attribute__((visibility("default"))) Archive *factory();
$ cat libimpl.cpp
#include "lib.h"
struct ArchiveImpl : Archive { void foo(); };
void ArchiveImpl::foo() {}
Archive *factory() { return new ArchiveImpl; }
$ cat main.cpp
#include "lib.h"
int main(void) {
factory()->foo();
}
$ make
g++ -fPIC -o libimpl.so -shared libimpl.cpp -fvisibility=hidden -Wall
-fsanitize=undefined -lubsan
g++ -o main main.cpp ./libimpl.so -fvisibility=hidden -Wall
-fsanitize=undefined -lubsan
$ ./main
main.cpp:3:16: runtime error: member call on address 0x000000dcfc20 which does
not point to an object of type 'Archive'
0x000000dcfc20: note: object is of type 'ArchiveImpl'
00 00 00 00 88 ed 59 dc 84 7f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 21 00 00 00
^~~~~~~~~~~~~~~~~~~~~~~
vptr for 'ArchiveImpl'
The symbol table of main or libimpl.so do not appear to change when
removing/adding -fvisiblity=hidden (no added/removed symbols, just address
changes), so I wonder what exactly it is that UBSAN is trying to look up and
not finding.
$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib64/gcc/x86_64-suse-linux/7/lto-wrapper
OFFLOAD_TARGET_NAMES=hsa:nvptx-none
Target: x86_64-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64
--enable-languages=c,c++,objc,fortran,obj-c++,ada,go
--enable-offload-targets=hsa,nvptx-none=/usr/nvptx-none, --without-cuda-driver
--enable-checking=release --disable-werror
--with-gxx-include-dir=/usr/include/c++/7 --enable-ssp --disable-libssp
--disable-libvtv --disable-libcc1 --enable-plugin
--with-bugurl=http://bugs.opensuse.org/ --with-pkgversion='SUSE Linux'
--with-slibdir=/lib64 --with-system-zlib --enable-__cxa_atexit
--enable-libstdcxx-allocator=new --disable-libstdcxx-pch
--enable-version-specific-runtime-libs --with-gcc-major-version-only
--enable-linker-build-id --enable-linux-futex --enable-gnu-indirect-function
--program-suffix=-7 --without-system-libunwind --enable-multilib
--with-arch-32=x86-64 --with-tune=generic --build=x86_64-suse-linux
--host=x86_64-suse-linux
Thread model: posix
gcc version 7.1.1 20170530 [gcc-7-branch revision 248621] (SUSE Linux)
