[LLVMbugs] [Bug 12116] New: Allow reinterpret_cast in constant expressions in microsoft mode

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12116

             Bug #: 12116
           Summary: Allow reinterpret_cast in constant expressions in
                    microsoft mode
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: nicolasweber at gmx.de
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified


When compiling ms headers with -nobuiltininc, clang picks up offsetof() from
msvc's stddef.h (
http://msdn.microsoft.com/en-us/library/dz4y9b9a(v=vs.80).aspx ). If it's used
with chrome's STATIC_ASSERT macro, clang complains about "reinterpret_cast not
allowed in constant expressions".

I came up with an offsetof() macro that exhibits the same error:

hummer:clang thakis$ cat test.cc
#define offsetof(s,m)   \
  (long)(void*)&((reinterpret_cast<s*>(0)->m))

template <bool>
struct GpuCompileAssert {
};

struct SetToken {
  int a, token;
};

GpuCompileAssert<(bool(offsetof(SetToken, token) == 4))> foo;




hummer:clang thakis$ ../../Release+Asserts/bin/clang -c test.cc -fms-extensions
-fms-compatibility
here4!
here3!
test.cc:12:18: error: non-type template argument of type 'bool' is not an
integral constant expression
GpuCompileAssert<(bool(offsetof(SetToken, token) == 4))> foo;
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test.cc:12:24: note: cast which performs the conversions of a reinterpret_cast
is not allowed in a constant expression
GpuCompileAssert<(bool(offsetof(SetToken, token) == 4))> foo;
                       ^
test.cc:2:3: note: expanded from macro 'offsetof'
  (long)(void*)&((reinterpret_cast<s*>(0)->m))
  ^
1 error generated.


We should allow reinterpret_cast<>()s in constant expressions in microsoft
mode.

-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.