[cfe-dev] Possible incompatible gcc attribute parsing with GCC

[Xiaolong Tang]

Hi all,

I am trying to see how far clang supports GNU attributes. It seems to
me that clang does not support declare attributes for members of
templates. Following is what I found:

I use a very simple test code (in template_attribute.cpp): 

  template<typename T> class vector {
  private:
    T rep[10];
  public:
    T top() { return rep[0]; }
  };

  template<typename T> T vector<T>::top() __attribute__ ((pure));

  int main()
  {
    vector<int> a;
    int r = a.top();
    int t = a.top();
    return r + t;
  }

With this command:

  g++ -O2 -cse -fno-inline -fdump-tree-all-all template_attribute.cpp

the above code gets compiled and optimized (CSE works here). 

However, trying to compile the code with clang generates the following
message:

  16:15:55->clang++ -c template_attribute.cpp
  
  template_attribute.cpp:9:35: error: out-of-line declaration of a member must be
        a definition [-Wout-of-line-declaration]
  template<typename T> T vector<T>::top() __attribute__ ((pure));
                         ~~~~~~~~~~~^
  template_attribute.cpp:9:35: warning: attribute declaration must precede
        definition
  template_attribute.cpp:5:5: note: previous definition is here
    T top() { return rep[0]; }
      ^
  1 warning and 1 error generated.

PS: clang version 2.9 (trunk 126848)

Best,
Xiaolong