Update from Gnulib

This incorporates:
2020-08-11 Use expression statements also on clang
2020-08-10 Use many __attribute__s with clang
2020-08-09 Use attribute __aligned__ with clang
2020-08-09 Use __alignof__ with clang
2020-08-09 ignore-value: Simplify on clang
2020-08-09 Use __typeof__ with clang
2020-08-09 intprops: Fix typo in comment
2020-08-09 Silence warnings from clang 10 with -Wimplicit-fallthrough
2020-08-09 count-one-bits: Use __builtin_popcount{,l,ll} on clang
2020-08-09 string: Fix build error in C++ mode with clang
2020-08-09 Add ability to emit user-defined diagnostics with clang
2020-08-07 alloca: No need to compile alloca.c with clang
2020-08-06 Use __builtin_assume with clang
* lib/alloca.in.h, lib/arg-nonnull.h, lib/c++defs.h, lib/cdefs.h:
* lib/count-one-bits.h, lib/dirent.in.h, lib/ignore-value.h:
* lib/intprops.h, lib/malloca.h, lib/regex_internal.h:
* lib/stdalign.in.h, lib/stddef.in.h, lib/stdio.in.h:
* lib/stdlib.in.h, lib/string.in.h, lib/verify.h, lib/warn-on-use.h:
* m4/gnulib-common.m4, m4/stddef_h.m4, m4/stdint.m4:
Copy from Gnulib.

3 files changed, 10 insertions, 6 deletions

diff --git a/m4/gnulib-common.m4 b/m4/gnulib-common.m4
index 50acc0a474b..03da2287d48 100644
--- a/m4/gnulib-common.m4
+++ b/m4/gnulib-common.m4
@@ -1,4 +1,4 @@
-# gnulib-common.m4 serial 53
+# gnulib-common.m4 serial 55
 dnl Copyright (C) 2007-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -45,7 +45,7 @@ AC_DEFUN([gl_COMMON_BODY], [
                 ? 6000000 <= __apple_build_version__ \
                 : 3 < __clang_major__ + (5 <= __clang_minor__))))
    /* _Noreturn works as-is.  */
-# elif _GL_GNUC_PREREQ (2, 8) || 0x5110 <= __SUNPRO_C
+# elif _GL_GNUC_PREREQ (2, 8) || defined __clang__ || 0x5110 <= __SUNPRO_C
 #  define _Noreturn __attribute__ ((__noreturn__))
 # elif 1200 <= (defined _MSC_VER ? _MSC_VER : 0)
 #  define _Noreturn __declspec (noreturn)
@@ -76,6 +76,7 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTR_cold _GL_GNUC_PREREQ (4, 3)
 # define _GL_ATTR_const _GL_GNUC_PREREQ (2, 95)
 # define _GL_ATTR_deprecated _GL_GNUC_PREREQ (3, 1)
+# define _GL_ATTR_diagnose_if 0
 # define _GL_ATTR_error _GL_GNUC_PREREQ (4, 3)
 # define _GL_ATTR_externally_visible _GL_GNUC_PREREQ (4, 1)
 # define _GL_ATTR_fallthrough _GL_GNUC_PREREQ (7, 0)
@@ -149,6 +150,9 @@ AC_DEFUN([gl_COMMON_BODY], [
 #if _GL_HAS_ATTRIBUTE (error)
 # define _GL_ATTRIBUTE_ERROR(msg) __attribute__ ((__error__ (msg)))
 # define _GL_ATTRIBUTE_WARNING(msg) __attribute__ ((__warning__ (msg)))
+#elif _GL_HAS_ATTRIBUTE (diagnose_if)
+# define _GL_ATTRIBUTE_ERROR(msg) __attribute__ ((__diagnose_if__ (1, msg, "error")))
+# define _GL_ATTRIBUTE_WARNING(msg) __attribute__ ((__diagnose_if__ (1, msg, "warning")))
 #else
 # define _GL_ATTRIBUTE_ERROR(msg)
 # define _GL_ATTRIBUTE_WARNING(msg)
diff --git a/m4/stddef_h.m4 b/m4/stddef_h.m4
index 6bcfadb74ef..d8bc8ff64e4 100644
--- a/m4/stddef_h.m4
+++ b/m4/stddef_h.m4
@@ -1,5 +1,5 @@
 dnl A placeholder for <stddef.h>, for platforms that have issues.
-# stddef_h.m4 serial 6
+# stddef_h.m4 serial 7
 dnl Copyright (C) 2009-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -19,7 +19,7 @@ AC_DEFUN([gl_STDDEF_H],
        [AC_LANG_PROGRAM(
           [[#include <stddef.h>
             unsigned int s = sizeof (max_align_t);
-            #if defined __GNUC__ || defined __IBM__ALIGNOF__
+            #if defined __GNUC__ || defined __clang__ || defined __IBM__ALIGNOF__
             int check1[2 * (__alignof__ (double) <= __alignof__ (max_align_t)) - 1];
             int check2[2 * (__alignof__ (long double) <= __alignof__ (max_align_t)) - 1];
             #endif
diff --git a/m4/stdint.m4 b/m4/stdint.m4
index 29ad826d8ea..e0fa8a51fb3 100644
--- a/m4/stdint.m4
+++ b/m4/stdint.m4
@@ -1,4 +1,4 @@
-# stdint.m4 serial 54
+# stdint.m4 serial 55
 dnl Copyright (C) 2001-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -152,7 +152,7 @@ uintmax_t j = UINTMAX_MAX;
 /* Check that SIZE_MAX has the correct type, if possible.  */
 #if 201112 <= __STDC_VERSION__
 int k = _Generic (SIZE_MAX, size_t: 0);
-#elif (2 <= __GNUC__ || defined __IBM__TYPEOF__ \
+#elif (2 <= __GNUC__ || 4 <= __clang_major__ || defined __IBM__TYPEOF__ \
        || (0x5110 <= __SUNPRO_C && !__STDC__))
 extern size_t k;
 extern __typeof__ (SIZE_MAX) k;