[clang-tidy] follow-up on misc-definitions-in-header check.

[hokein]

Summary

A follow-up on D34449:

• add -std=c++11 to .hpp file by default.
• add constexpr function to test and doc.

[alexfh]

LG

docs/clang-tidy/checks/misc-definitions-in-headers.rst

.. code-block:: c++
    class CE {
      constexpr static int i = 5; // OK: inline variable definition.
    };
 
    inline int i = 5; // OK: inline variable definition.
 
    constexpr int k = 1; // OK: constexpr variable has internal linkage.
 
+   constexpr int f10() { return 0; } // OK: constexpr function definition.
+
 Options
 -------
 
 .. option:: HeaderFileExtensions
 
    A comma-separated list of filename extensions of header files (the filename
    extensions should not include "." prefix). Default is "h,hh,hpp,hxx".
    For header files without an extension, use an empty string (if there are no
    other desired extensions) or leave an empty element in the list. e.g.,
    "h,hh,hpp,hxx," (note the trailing comma).
 
 .. option:: UseHeaderFileExtension
 
    When non-zero, the check will use the file extension to distinguish header
    files. Default is `1`.

test/clang-tidy/check_clang_tidy.py

def main():
   if (input_file_name.endswith('.c')):
     extension = '.c'
   if (input_file_name.endswith('.hpp')):
     extension = '.hpp'
   temp_file_name = temp_file_name + extension
 
   clang_tidy_extra_args = extra_args
   if len(clang_tidy_extra_args) == 0:
-    clang_tidy_extra_args = ['--', '--std=c++11'] if extension == '.cpp' \
-                       else ['--']
+    clang_tidy_extra_args = ['--', '--std=c++11'] \
+        if extension == '.cpp' or extension == '.hpp' else ['--']
 
   # Tests should not rely on STL being available, and instead provide mock
   # implementations of relevant APIs.
   clang_tidy_extra_args.append('-nostdinc++')
 
   if resource_dir is not None:
     clang_tidy_extra_args.append('-resource-dir=%s' % resource_dir)
 

test/clang-tidy/misc-definitions-in-headers.hpp

-// RUN: %check_clang_tidy %s misc-definitions-in-headers %t -- -- -std=c++11
+// RUN: %check_clang_tidy %s misc-definitions-in-headers %t
 
 int f() {
 // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'f' defined in a header file; function definitions in header files can lead to ODR violations [misc-definitions-in-headers]
 // CHECK-FIXES: inline int f() {
   return 1;
 }
 
 class CA {

 }
 
 template <typename T>
 int CD<T, int>::f() { // OK: partial template specialization.
   return 0;
 }
 
 constexpr int k = 1; // OK: constexpr variable has internal linkage.
+
+constexpr int f10() { return 0; } // OK: constexpr function definition.