libsanitizer in GCC 10 is dropping symbols without bumping the soversions

[Martin Liška]

On 11/29/19 12:47 PM, Jakub Jelinek wrote:
> __ubsan_handle_function_type_mismatch* is something we don't use (Martin,
> should we add such sanitizer?  We have gimple_call_fntype vs. actual decl
> types, but it would need some inspection on what the sanitizer really does),
> but still e.g. clang compiled binaries could and could be (at least in
> theory) be linked against gcc libubsan.

Yes, we can add it for GCC 11. The sanitizer is about:

$ cat indirect.C
int foo(int a)
{
   return a;
}

void bar(int (*fn) (void))
{
   fn();
}

int main()
{
   bar(reinterpret_cast<int (*)(void)> (foo));
}

$ clang++ indirect.C -fsanitize=function && ./a.out
indirect.C:8:3: runtime error: call to function foo(int) through pointer to incorrect function type 'int (*)()'
(/tmp/a.out+0x424c60): note: foo(int) defined here
     #0 0x424cfb in bar(int (*)()) (/tmp/a.out+0x424cfb)
     #1 0x424d2d in main (/tmp/a.out+0x424d2d)
     #2 0x7f2e8bbfee0a in __libc_start_main /usr/src/debug/glibc-2.30-1.2.x86_64/csu/../csu/libc-start.c:308:16
     #3 0x403309 in _start /home/abuild/rpmbuild/BUILD/glibc-2.30/csu/../sysdeps/x86_64/start.S:120

static bool handleFunctionTypeMismatch(FunctionTypeMismatchData *Data,
                                        ValueHandle Function,
                                        ValueHandle calleeRTTI,
                                        ValueHandle fnRTTI, ReportOptions Opts) {
   if (checkTypeInfoEquality(reinterpret_cast<void *>(calleeRTTI),
                             reinterpret_cast<void *>(fnRTTI)))
     return false;

So it should be quite trivial as we're already using checkTypeInfoEquality in
bool __ubsan::checkDynamicType(void *Object, void *Type, HashValue Hash) {

Martin