警告(不合时宜)：将 void(*)(int) 分配给 extern "C" void(*)(int)

我在使用Sun的c++编译器时遇到了麻烦。我读过Oracle的《使用指针指向函数》[来自c++]。这是一个很好的阅读，我得到的印象是SunCC是这个领域所有编译器中最兼容的(尽管它给我带来了麻烦)。

测试代码如下，第24行是new_handler.sa_handler = (pfn ? pfn : &SignalHandler::NullHandler);。展开三元运算符显示出问题所在:new_handler.sa_handler = pfn; .

SunCC 5.11

$ /opt/solstudio12.2/bin/CC test.cxx
"test.cxx", line 24: Warning (Anachronism): Assigning void(*)(int) to extern "C" void(*)(int).
"test.cxx", line 58:     Where: While instantiating "SignalHandler<5, 0>::SignalHandler(void(*)(int), int)".
"test.cxx", line 58:     Where: Instantiated from non-template code.

SunCC 5.12

$ /opt/solarisstudio12.3/bin/CC test.cxx
"test.cxx", line 24: Warning (Anachronism): Assigning void(*)(int) to extern "C" void(*)(int).
"test.cxx", line 58:     Where: While instantiating "SignalHandler<5, 0>::SignalHandler(void(*)(int), int)".
"test.cxx", line 58:     Where: Instantiated from non-template code.

SunCC 5.13

$ /opt/solarisstudio12.4/bin/CC test.cxx
"test.cxx", line 24: Warning (Anachronism): Using void(*)(int) to initialize extern "C" void(*)(int).
"test.cxx", line 58:     Where: While instantiating "SignalHandler<5, 0>::SignalHandler(void(*)(int), int)".
"test.cxx", line 58:     Where: Instantiated from non-template code.

SunCC 5.14

$ /opt/developerstudio12.5/bin/CC test.cxx
$

我不太清楚问题出在哪里。这里有一个类似的问题在Oracle板，但OP基本上是告诉RTFM: Sun Studio 11"警告(时代错误)"。

如何解决时间错误警告?

---

solaris:~$ cat test.cxx
#include <signal.h>
extern "C" {
  typedef void (*SignalHandlerFn) (int);
};
template <int S, bool O=false>
struct SignalHandler
{
  SignalHandler(SignalHandlerFn pfn = NULL, int flags = 0) : m_installed(false)
  {
    struct sigaction new_handler;
    do
    {
      int ret = 0;
      ret = sigaction (S, 0, &m_old);
      if (ret != 0) break; // Failed
      if (m_old.sa_handler != 0 && !O) break;
      new_handler.sa_handler = (pfn ? pfn : &SignalHandler::NullHandler);
      new_handler.sa_flags = (pfn ? flags : 0);
      ret = sigemptyset (&new_handler.sa_mask);
      if (ret != 0) break; // Failed
      ret = sigaction (S, &new_handler, 0);
      if (ret != 0) break; // Failed
      m_installed = true;
    } while(0);
  }
  ~SignalHandler()
  {
    if (m_installed)
      sigaction (S, &m_old, 0);
  }
private:
  struct sigaction m_old;
  bool m_installed;
  static void NullHandler(int /*unused*/) { /* continue*/ }
private:
  // Not copyable
  SignalHandler(const SignalHandler &);
  void operator=(const SignalHandler &);
};
int main(int argc, char* argv[])
{
  SignalHandler<SIGTRAP, 0> handler;
  return 0;
}

pfn ? pfn : &SignalHandler::NullHandler