c-family: Support #pragma region/endregion [PR85487]

These pragmas are used by some editors to mark regions of code for
grouping and folding. GCC should silently ignore them, rather than
giving -Wunknown-pragmas warnings.

	PR c/85487

gcc/ChangeLog:

	* doc/cpp/pragmas.rst (Pragmas): Document region pragmas.

gcc/c-family/ChangeLog:

	* c-pragma.cc (handle_pragma_ignore): New function.
	(init_pragma): Register region and endregion pragmas.

gcc/testsuite/ChangeLog:

	* c-c++-common/pragma-region.c: New test.

1 files changed, 9 insertions, 0 deletions

diff --git a/gcc/c-family/c-pragma.cc b/gcc/c-family/c-pragma.cc
index b5a4b3c..142a464 100644
--- a/gcc/c-family/c-pragma.cc
+++ b/gcc/c-family/c-pragma.cc
@@ -1403,6 +1403,12 @@ handle_pragma_message (cpp_reader *)
 	    TREE_STRING_POINTER (message));
 }
 
+/* Ignore a no-op pragma that GCC recognizes, but which has no effect.  */
+static void
+handle_pragma_ignore (cpp_reader *)
+{
+}
+
 /* Mark whether the current location is valid for a STDC pragma.  */
 
 static bool valid_location_for_stdc_pragma;
@@ -1870,6 +1876,9 @@ init_pragma (void)
   c_register_pragma ("GCC", "pop_options", handle_pragma_pop_options);
   c_register_pragma ("GCC", "reset_options", handle_pragma_reset_options);
 
+  c_register_pragma (0, "region", handle_pragma_ignore);
+  c_register_pragma (0, "endregion", handle_pragma_ignore);
+
   c_register_pragma ("STDC", "FLOAT_CONST_DECIMAL64",
 		     handle_pragma_float_const_decimal64);