[cfe-dev] -fsanitize=undefined and shared libraries

[Martin Martin]

When trying to use -fsanitize=undefined with shared libraries, I get:

/usr/bin/ld: a.out: hidden symbol `__ubsan_handle_float_cast_overflow' in
/home/clang/build-cmake/bin/../lib/clang/3.2/lib/linux/libclang_rt.ubsan-x86_64.a(ubsan_handlers.cc.o)
is referenced by DSO
/usr/bin/ld: final link failed: Bad value
clang-3: error: linker command failed with exit code 1 (use -v to see
invocation)

This is with Clang 3.2 compiled from sources using cmake, on Ubuntu 12.10.

I'm compiling my files like this:

clang++ -fPIC -fsanitize=undefined undefined.cpp -c -o undefined.o
clang++ -shared -Wl,-soname,libfoo.so undefined.o -o libfoo.so
clang++ -fsanitize=undefined main.cpp -c -o main.o
clang++ -fsanitize=undefined main.o -L. -lfoo

$ cat undefined.cpp
int cast(float x) {
    return int(x);
}

$ cat main.cpp
#include <cstdlib>

extern int cast(float x);

int main(int argc, char *argv[])
{
    if (argc > 1) {
        return cast(atof(argv[1]));
    }

    return 1;
}

If I don't use shared libraries, but instead like the two .o files (without
the -fPIC), it works fine, I get:

./a.out 1e10
<unknown>: fatal error: value 1e+10 is outside the range of representable
values of type 'int'
Illegal instruction (core dumped)


Any idea what I'm doing wrong?

Thanks,
Martin
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