[llvm-bugs] [Bug 31002] New: clang rejects valid C++ code with variable argument function

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=31002

            Bug ID: 31002
           Summary: clang rejects valid C++ code with variable argument
                    function
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org
    Classification: Unclassified

It seems to affect all clang versions since at least as early as 3.2.x, and is
also incorrectly rejected by ICC. 

Both GCC and MSVC correctly accept the code. 

The code is accepted if the destructor is commented out. 


$ clang++ -v
clang version 4.0.0 (trunk 286715)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/clang-trunk/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$
$ g++-6.2 small.cpp
$
$ clang++ small.cpp
small.cpp:12:20: error: second argument to 'va_arg' is of non-POD type 'A'
[-Wnon-pod-varargs]
  A v = va_arg (a, A);
                   ^
/usr/local/clang-trunk/bin/../lib/clang/4.0.0/include/stdarg.h:35:50: note:
expanded from macro 'va_arg'
#define va_arg(ap, type)    __builtin_va_arg(ap, type)
                                                 ^~~~
small.cpp:19:11: error: cannot pass object of non-POD type 'A' through variadic
function; call will abort at runtime
      [-Wnon-pod-varargs]
  foo (t, t);
          ^
2 errors generated.
$


----------------------------


#include <cstdarg>

struct A
{ 
  virtual ~A () {}
};

void foo (A p, ...)
{ 
  va_list a;
  va_start (a, p);
  A v = va_arg (a, A);
  va_end (a);
}

int main ()
{ 
  A t;
  foo (t, t);
  return 0;
}

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