Add cc.has_function_attribute('sentinel')

docs/markdown/Reference-tables.md

@@ -247,6 +247,7 @@ which are supported by GCC, Clang, and other compilers.
 | retain⁴                  |
 | returns_nonnull          |
 | section⁵                 |
+| sentinel⁵                |
 | unused                   |
 | used                     |
 | visibility*              |

mesonbuild/compilers/c_function_attributes.py

@@ -94,6 +94,8 @@ C_FUNC_ATTRIBUTES = {
         #else
             extern int foo __attribute__((section(".bar")));
         #endif''',
+    'sentinel':
+        'int foo(const char *bar, ...) __attribute__((sentinel));',
     'unused':
         'int foo(void) __attribute__((unused));',
     'used':

test cases/common/197 function attributes/meson.build

@@ -50,6 +50,7 @@ attributes = [
   'nothrow',
   'pure',
   'section',
+  'sentinel',
   'unused',
   'used',
   'warn_unused_result',