c: support the attribute starting with '_'

	PR c/107156

gcc/ChangeLog:

	* attribs.h (lookup_attribute_by_prefix): Support the attribute
	starting with underscore (_Noreturn).

diff --git a/gcc/attribs.h b/gcc/attribs.h
index b2836560fc215ceebc2d9e847776b7cda295137a..121b9ebbc39ac755af5e1c182a4ebb62ac4238b0 100644 (file)
--- a/gcc/attribs.h
+++ b/gcc/attribs.h
@@ -274,8 +274,8 @@ lookup_attribute_by_prefix (const char *attr_name, tree list)
            }
 
          const char *p = IDENTIFIER_POINTER (name);
-         gcc_checking_assert (attr_len == 0 || p[0] != '_');
-
+         gcc_checking_assert (attr_len == 0 || p[0] != '_'
+                              || (ident_len > 1 && p[1] != '_'));
          if (strncmp (attr_name, p, attr_len) == 0)
            break;