[LLVMbugs] [Bug 17813] New: Class without default constructor, but with destructor is not trivially constructible

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Nov 5 05:02:18 PST 2013


            Bug ID: 17813
           Summary: Class without default constructor, but with destructor
                    is not trivially constructible
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++11
          Assignee: unassignedclangbugs at nondot.org
          Reporter: jonathan.sauer at gmx.de
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The following code does not compile with clang r193986:

struct Foo {

static_assert(__is_trivially_constructible(Foo), "");
static_assert(__has_trivial_constructor(Foo), "");

This results in:

% ~/LLVM/build/Release+Asserts/bin/clang -c -std=c++11 clang.cpp                
clang.cpp:5:1: error: static_assert failed ""
static_assert(__is_trivially_constructible(Foo), "");
^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

Removing the destructor makes the code compile.

This looks like an inconsistency between __is_trivially_constructible and
__has_trivial_constructor, the former of which are used by libc++'s
std::is_trivially_constructible type trait (the latter is only used if the
former is not available).

Also __is_trivially_constructible is influenced by the existence of a
destructor, despite §12.1p5 not mentioning destructors:

| A default constructor is trivial if it is not user-provided and if:
| — its class has no virtual functions (10.3) and no virtual base classes
|   (10.1), and
| — no non-static data member of its class has a brace-or-equal-initializer,
|   and
| — all the direct base classes of its class have trivial default constructors,
|   and
| — for all the non-static data members of its class that are of class type
|   (or array thereof), each such class has a trivial default constructor.

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