[PATCH 2/2] verify: work around xlclang 16.1 compiler bug

[Paul Eggert]

Problem reported by Bruno Haible in:
https://lists.gnu.org/r/grep-devel/2023-01/msg00003.html
* lib/verify.h (_GL_HAS_BUILTIN_TRAP, _GL_HAS_BUILTIN_UNREACHABLE):
Define to 0 if compiler advertises itself as clang before version 5.
xlclang 16.1 advertises itself as 4.0.1 and this patch works
around what appears to be a compiler bug when compiling dfa.c in
bleeding-edge grep.
---
 ChangeLog    | 9 +++++++++
 lib/verify.h | 8 ++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 3799832c09..dc8fb2c12b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,14 @@
 2023-01-13  Paul Eggert  <eggert@cs.ucla.edu>
 
+       verify: work around xlclang 16.1 compiler bug
+       Problem reported by Bruno Haible in:
+       https://lists.gnu.org/r/grep-devel/2023-01/msg00003.html
+       * lib/verify.h (_GL_HAS_BUILTIN_TRAP, _GL_HAS_BUILTIN_UNREACHABLE):
+       Define to 0 if compiler advertises itself as clang before version 5.
+       xlclang 16.1 advertises itself as 4.0.1 and this patch works
+       around what appears to be a compiler bug when compiling dfa.c in
+       bleeding-edge grep.
+
        assert-h: suppress xlclang 16.1 false alarms
        * m4/assert_h.m4 (gl_ASSERT_H): Pacify older clangs too,
        with regard to single-argument static_assert.
diff --git a/lib/verify.h b/lib/verify.h
index 17d6e78c81..b63cb26432 100644
--- a/lib/verify.h
+++ b/lib/verify.h
@@ -258,7 +258,9 @@ template <int w>
 
 /* @assert.h omit start@  */
 
-#if 3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__))
+#if defined __clang_major__ && __clang_major__ < 5
+# define _GL_HAS_BUILTIN_TRAP 0
+#elif 3 < __GNUC__ + (3 < __GNUC_MINOR__ + (4 <= __GNUC_PATCHLEVEL__))
 # define _GL_HAS_BUILTIN_TRAP 1
 #elif defined __has_builtin
 # define _GL_HAS_BUILTIN_TRAP __has_builtin (__builtin_trap)
@@ -266,7 +268,9 @@ template <int w>
 # define _GL_HAS_BUILTIN_TRAP 0
 #endif
 
-#if 4 < __GNUC__ + (5 <= __GNUC_MINOR__)
+#if defined __clang_major__ && __clang_major__ < 5
+# define _GL_HAS_BUILTIN_UNREACHABLE 0
+#elif 4 < __GNUC__ + (5 <= __GNUC_MINOR__)
 # define _GL_HAS_BUILTIN_UNREACHABLE 1
 #elif defined __has_builtin
 # define _GL_HAS_BUILTIN_UNREACHABLE __has_builtin (__builtin_unreachable)
-- 
2.37.2