http://llvm.org/bugs/show_bug.cgi?id=18058
Bug ID: 18058
Summary: UBSan SEGFAULTs rendering memory at 0x00000001
Product: compiler-rt
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: compiler-rt
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
I'm trying to run some code through UBSan, but it crashes when trying to print
memory at address 0x00000001. The code in question comes from
boost::serialization 1.54:
boost/serialization/void_cast.hpp:187:13
// note:I wanted to display from 0 here, but at least one compiler
// treated 0 by not shifting it at all.
reinterpret_cast<std::ptrdiff_t>(
static_cast<Derived *>(
reinterpret_cast<Base *>(1)
)
) - 1
UBSan crashes because it detects a misaligned downcasts, after which it tries
to read the memory at 0xx00000001:
/boost/serialization/void_cast.hpp:187:13: runtime error: downcast of
misaligned address 0x00000001 for type 'BundleRFRead',
which requires 4 byte alignment
0x00000001: note: pointer points here
Program received signal SIGSEGV, Segmentation fault.
0x089c36dd in getMemoryLocation () at
llvm/projects/compiler-rt/lib/ubsan/ubsan_diag.cc:191
191 Printf("%s%02x", (P % 8 == 0) ? " " : " ", C);
This is on ToT, with the backtrace as follows:
#0 0x089c36dd in getMemoryLocation ()
at llvm/projects/compiler-rt/lib/ubsan/ubsan_diag.cc:191
#1 ~Diag ()
at llvm/projects/compiler-rt/lib/ubsan/ubsan_diag.cc:271
#2 0x089c412f in handleTypeMismatchImpl ()
at llvm/projects/compiler-rt/lib/ubsan/ubsan_handlers.cc:52
#3 0x089c3b8f in __ubsan_handle_type_mismatch ()
at llvm/projects/compiler-rt/lib/ubsan/ubsan_handlers.cc:56
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