Update support files from GNULIB.

8 files changed, 205 insertions, 104 deletions

diff --git a/support/ChangeLog b/support/ChangeLog
index 0b14f6a6..5f6e7bc2 100644
--- a/support/ChangeLog
+++ b/support/ChangeLog
@@ -1,3 +1,8 @@
+2020-09-18         Arnold D. Robbins     <arnold@skeeve.com>
+
+	* cdefs.h, dfa.c, intprops.h, regcomp.c, regex.h, regex_internal.h,
+	verify.h: Synced from GNULIB.
+
 2020-09-14         Arnold D. Robbins     <arnold@skeeve.com>
 
 	* dfa.c: Synced from GNULIB.
diff --git a/support/cdefs.h b/support/cdefs.h
index 21583795..b4ac4df6 100644
--- a/support/cdefs.h
+++ b/support/cdefs.h
@@ -34,7 +34,34 @@
 #undef	__P
 #undef	__PMT
 
-#ifdef __GNUC__
+/* Compilers that are not clang may object to
+       #if defined __clang__ && __has_attribute(...)
+   even though they do not need to evaluate the right-hand side of the &&.  */
+#if defined __clang__ && defined __has_attribute
+# define __glibc_clang_has_attribute(name) __has_attribute (name)
+#else
+# define __glibc_clang_has_attribute(name) 0
+#endif
+
+/* Compilers that are not clang may object to
+       #if defined __clang__ && __has_builtin(...)
+   even though they do not need to evaluate the right-hand side of the &&.  */
+#if defined __clang__ && defined __has_builtin
+# define __glibc_clang_has_builtin(name) __has_builtin (name)
+#else
+# define __glibc_clang_has_builtin(name) 0
+#endif
+
+/* Compilers that are not clang may object to
+       #if defined __clang__ && __has_extension(...)
+   even though they do not need to evaluate the right-hand side of the &&.  */
+#if defined __clang__ && defined __has_extension
+# define __glibc_clang_has_extension(ext) __has_extension (ext)
+#else
+# define __glibc_clang_has_extension(ext) 0
+#endif
+
+#if defined __GNUC__ || defined __clang__
 
 /* All functions, except those with callbacks or those that
    synchronize memory, are leaf functions.  */
@@ -48,16 +75,17 @@
 
 /* GCC can always grok prototypes.  For C++ programs we add throw()
    to help it optimize the function calls.  But this works only with
-   gcc 2.8.x and egcs.  For gcc 3.2 and up we even mark C functions
+   gcc 2.8.x and egcs.  For gcc 3.4 and up we even mark C functions
    as non-throwing using a function attribute since programs can use
    the -fexceptions options for C code as well.  */
-# if !defined __cplusplus && __GNUC_PREREQ (3, 3)
+# if !defined __cplusplus \
+     && (__GNUC_PREREQ (3, 4) || __glibc_clang_has_attribute (__nothrow__))
 #  define __THROW	__attribute__ ((__nothrow__ __LEAF))
 #  define __THROWNL	__attribute__ ((__nothrow__))
 #  define __NTH(fct)	__attribute__ ((__nothrow__ __LEAF)) fct
 #  define __NTHNL(fct)  __attribute__ ((__nothrow__)) fct
 # else
-#  if defined __cplusplus && __GNUC_PREREQ (2,8)
+#  if defined __cplusplus && (__GNUC_PREREQ (2,8) || __clang_major >= 4)
 #   define __THROW	throw ()
 #   define __THROWNL	throw ()
 #   define __NTH(fct)	__LEAF_ATTR fct throw ()
@@ -70,7 +98,7 @@
 #  endif
 # endif
 
-#else	/* Not GCC.  */
+#else	/* Not GCC or clang.  */
 
 # if (defined __cplusplus						\
       || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L))
@@ -83,16 +111,7 @@
 # define __THROWNL
 # define __NTH(fct)	fct
 
-#endif	/* GCC.  */
-
-/* Compilers that are not clang may object to
-       #if defined __clang__ && __has_extension(...)
-   even though they do not need to evaluate the right-hand side of the &&.  */
-#if defined __clang__ && defined __has_extension
-# define __glibc_clang_has_extension(ext) __has_extension (ext)
-#else
-# define __glibc_clang_has_extension(ext) 0
-#endif
+#endif	/* GCC || clang.  */
 
 /* These two macros are not used in glibc anymore.  They are kept here
    only because some other projects expect the macros to be defined.  */
@@ -129,6 +148,16 @@
 # define __warnattr(msg) __attribute__((__warning__ (msg)))
 # define __errordecl(name, msg) \
   extern void name (void) __attribute__((__error__ (msg)))
+#elif __glibc_clang_has_attribute (__diagnose_if__) && 0
+/* These definitions are not enabled, because they produce bogus warnings
+   in the glibc Fortify functions.  These functions are written in a style
+   that works with GCC.  In order to work with clang, these functions would
+   need to be modified.  */
+# define __warndecl(name, msg) \
+  extern void name (void) __attribute__((__diagnose_if__ (1, msg, "warning")))
+# define __warnattr(msg) __attribute__((__diagnose_if__ (1, msg, "warning")))
+# define __errordecl(name, msg) \
+  extern void name (void) __attribute__((__diagnose_if__ (1, msg, "error")))
 #else
 # define __warndecl(name, msg) extern void name (void)
 # define __warnattr(msg)
@@ -142,8 +171,8 @@
 #if defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L && !defined __HP_cc
 # define __flexarr	[]
 # define __glibc_c99_flexarr_available 1
-#elif __GNUC_PREREQ (2,97)
-/* GCC 2.97 supports C99 flexible array members as an extension,
+#elif __GNUC_PREREQ (2,97) || defined __clang__
+/* GCC 2.97 and clang support C99 flexible array members as an extension,
    even when in C89 mode or compiling C++ (any version).  */
 # define __flexarr	[]
 # define __glibc_c99_flexarr_available 1
@@ -169,7 +198,7 @@
    Example:
    int __REDIRECT(setpgrp, (__pid_t pid, __pid_t pgrp), setpgid); */
 
-#if defined __GNUC__ && __GNUC__ >= 2
+#if (defined __GNUC__ && __GNUC__ >= 2) || (__clang_major__ >= 4)
 
 # define __REDIRECT(name, proto, alias) name proto __asm__ (__ASMNAME (#alias))
 # ifdef __cplusplus
@@ -194,17 +223,17 @@
 */
 #endif
 
-/* GCC has various useful declarations that can be made with the
-   `__attribute__' syntax.  All of the ways we use this do fine if
-   they are omitted for compilers that don't understand it. */
-#if !defined __GNUC__ || __GNUC__ < 2
+/* GCC and clang have various useful declarations that can be made with
+   the '__attribute__' syntax.  All of the ways we use this do fine if
+   they are omitted for compilers that don't understand it.  */
+#if !(defined __GNUC__ || defined __clang__)
 # define __attribute__(xyz)	/* Ignore */
 #endif
 
 /* At some point during the gcc 2.96 development the `malloc' attribute
    for functions was introduced.  We don't want to use it unconditionally
    (although this would be possible) since it generates warnings.  */
-#if __GNUC_PREREQ (2,96)
+#if __GNUC_PREREQ (2,96) || __glibc_clang_has_attribute (__malloc__)
 # define __attribute_malloc__ __attribute__ ((__malloc__))
 #else
 # define __attribute_malloc__ /* Ignore */
@@ -222,14 +251,14 @@
 /* At some point during the gcc 2.96 development the `pure' attribute
    for functions was introduced.  We don't want to use it unconditionally
    (although this would be possible) since it generates warnings.  */
-#if __GNUC_PREREQ (2,96)
+#if __GNUC_PREREQ (2,96) || __glibc_clang_has_attribute (__pure__)
 # define __attribute_pure__ __attribute__ ((__pure__))
 #else
 # define __attribute_pure__ /* Ignore */
 #endif
 
 /* This declaration tells the compiler that the value is constant.  */
-#if __GNUC_PREREQ (2,5)
+#if __GNUC_PREREQ (2,5) || __glibc_clang_has_attribute (__const__)
 # define __attribute_const__ __attribute__ ((__const__))
 #else
 # define __attribute_const__ /* Ignore */
@@ -238,7 +267,7 @@
 /* At some point during the gcc 3.1 development the `used' attribute
    for functions was introduced.  We don't want to use it unconditionally
    (although this would be possible) since it generates warnings.  */
-#if __GNUC_PREREQ (3,1)
+#if __GNUC_PREREQ (3,1) || __glibc_clang_has_attribute (__used__)
 # define __attribute_used__ __attribute__ ((__used__))
 # define __attribute_noinline__ __attribute__ ((__noinline__))
 #else
@@ -247,7 +276,7 @@
 #endif
 
 /* Since version 3.2, gcc allows marking deprecated functions.  */
-#if __GNUC_PREREQ (3,2)
+#if __GNUC_PREREQ (3,2) || __glibc_clang_has_attribute (__deprecated__)
 # define __attribute_deprecated__ __attribute__ ((__deprecated__))
 #else
 # define __attribute_deprecated__ /* Ignore */
@@ -270,7 +299,7 @@
    If several `format_arg' attributes are given for the same function, in
    gcc-3.0 and older, all but the last one are ignored.  In newer gccs,
    all designated arguments are considered.  */
-#if __GNUC_PREREQ (2,8)
+#if __GNUC_PREREQ (2,8) || __glibc_clang_has_attribute (__format_arg__)
 # define __attribute_format_arg__(x) __attribute__ ((__format_arg__ (x)))
 #else
 # define __attribute_format_arg__(x) /* Ignore */
@@ -280,7 +309,7 @@
    attribute for functions was introduced.  We don't want to use it
    unconditionally (although this would be possible) since it
    generates warnings.  */
-#if __GNUC_PREREQ (2,97)
+#if __GNUC_PREREQ (2,97) || __glibc_clang_has_attribute (__format__)
 # define __attribute_format_strfmon__(a,b) \
   __attribute__ ((__format__ (__strfmon__, a, b)))
 #else
@@ -291,7 +320,7 @@
    must not be NULL.  Do not define __nonnull if it is already defined,
    for portability when this file is used in Gnulib.  */
 #ifndef __nonnull
-# if __GNUC_PREREQ (3,3)
+# if __GNUC_PREREQ (3,3) || __glibc_clang_has_attribute (__nonnull__)
 #  define __nonnull(params) __attribute__ ((__nonnull__ params))
 # else
 #  define __nonnull(params)
@@ -300,7 +329,7 @@
 
 /* If fortification mode, we warn about unused results of certain
    function calls which can lead to problems.  */
-#if __GNUC_PREREQ (3,4)
+#if __GNUC_PREREQ (3,4) || __glibc_clang_has_attribute (__warn_unused_result__)
 # define __attribute_warn_unused_result__ \
    __attribute__ ((__warn_unused_result__))
 # if defined __USE_FORTIFY_LEVEL && __USE_FORTIFY_LEVEL > 0
@@ -314,7 +343,7 @@
 #endif
 
 /* Forces a function to be always inlined.  */
-#if __GNUC_PREREQ (3,2)
+#if __GNUC_PREREQ (3,2) || __glibc_clang_has_attribute (__always_inline__)
 /* The Linux kernel defines __always_inline in stddef.h (283d7573), and
    it conflicts with this definition.  Therefore undefine it first to
    allow either header to be included first.  */
@@ -327,7 +356,7 @@
 
 /* Associate error messages with the source location of the call site rather
    than with the source location inside the function.  */
-#if __GNUC_PREREQ (4,3)
+#if __GNUC_PREREQ (4,3) || __glibc_clang_has_attribute (__artificial__)
 # define __attribute_artificial__ __attribute__ ((__artificial__))
 #else
 # define __attribute_artificial__ /* Ignore */
@@ -370,12 +399,14 @@
    run in pedantic mode if the uses are carefully marked using the
    `__extension__' keyword.  But this is not generally available before
    version 2.8.  */
-#if !__GNUC_PREREQ (2,8)
+#if !(__GNUC_PREREQ (2,8) || defined __clang__)
 # define __extension__		/* Ignore */
 #endif
 
-/* __restrict is known in EGCS 1.2 and above. */
-#if !__GNUC_PREREQ (2,92)
+/* __restrict is known in EGCS 1.2 and above, and in clang.
+   It works also in C++ mode (outside of arrays), but only when spelled
+   as '__restrict', not 'restrict'.  */
+#if !(__GNUC_PREREQ (2,92) || __clang_major__ >= 3)
 # if defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L
 #  define __restrict	restrict
 # else
@@ -385,8 +416,9 @@
 
 /* ISO C99 also allows to declare arrays as non-overlapping.  The syntax is
      array_name[restrict]
-   GCC 3.1 supports this.  */
-#if __GNUC_PREREQ (3,1) && !defined __GNUG__
+   GCC 3.1 and clang support this.
+   This syntax is not usable in C++ mode.  */
+#if (__GNUC_PREREQ (3,1) || __clang_major__ >= 3) && !defined __cplusplus
 # define __restrict_arr	__restrict
 #else
 # ifdef __GNUC__
@@ -401,7 +433,7 @@
 # endif
 #endif
 
-#if __GNUC__ >= 3
+#if (__GNUC__ >= 3) || __glibc_clang_has_builtin (__builtin_expect)
 # define __glibc_unlikely(cond)	__builtin_expect ((cond), 0)
 # define __glibc_likely(cond)	__builtin_expect ((cond), 1)
 #else
@@ -417,7 +449,8 @@
 
 #if (!defined _Noreturn \
      && (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) < 201112 \
-     &&  !__GNUC_PREREQ (4,7))
+     &&  !(__GNUC_PREREQ (4,7) \
+           || (3 < __clang_major__ + (5 <= __clang_minor__))))
 # if __GNUC_PREREQ (2,8)
 #  define _Noreturn __attribute__ ((__noreturn__))
 # else
@@ -436,7 +469,8 @@
 
 #if (!defined _Static_assert && !defined __cplusplus \
      && (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) < 201112 \
-     && (!__GNUC_PREREQ (4, 6) || defined __STRICT_ANSI__))
+     && (!(__GNUC_PREREQ (4, 6) || __clang_major__ >= 4) \
+         || defined __STRICT_ANSI__))
 # define _Static_assert(expr, diagnostic) \
     extern int (*__Static_assert_function (void)) \
       [!!sizeof (struct { int __error_if_negative: (expr) ? 2 : -1; })]
diff --git a/support/dfa.c b/support/dfa.c
index 8a012ad6..641f422a 100644
--- a/support/dfa.c
+++ b/support/dfa.c
@@ -2505,11 +2505,6 @@ reorder_tokens (struct dfa *d)
                           : NULL);
 
   for (idx_t i = 0; i < d->tindex; i++)
-    for (idx_t j = 0; j < d->follows[i].nelem; j++)
-      if (map[d->follows[i].elems[j].index] < 0)
-        map[d->follows[i].elems[j].index] = nleaves++;
-
-  for (idx_t i = 0; i < d->tindex; i++)
     {
       if (map[i] < 0)
         {
@@ -2527,7 +2522,12 @@ reorder_tokens (struct dfa *d)
         multibyte_prop[map[i]] = d->multibyte_prop[i];
 
       for (idx_t j = 0; j < d->follows[i].nelem; j++)
-        d->follows[i].elems[j].index = map[d->follows[i].elems[j].index];
+        {
+          if (map[d->follows[i].elems[j].index] == -1)
+            map[d->follows[i].elems[j].index] = nleaves++;
+
+          d->follows[i].elems[j].index = map[d->follows[i].elems[j].index];
+        }
 
       qsort (d->follows[i].elems, d->follows[i].nelem,
              sizeof *d->follows[i].elems, compare);
@@ -2700,6 +2700,17 @@ dfaanalyze (struct dfa *d, bool searchflag)
 
         case STAR:
         case PLUS:
+          /* Every element in the lastpos of the argument is in the backward
+             set of every element in the firstpos.  */
+          if (d->epsilon)
+            {
+              tmp.elems = lastpos - stk[-1].nlastpos;
+              tmp.nelem = stk[-1].nlastpos;
+              for (position *p = firstpos - stk[-1].nfirstpos;
+                   p < firstpos; p++)
+                merge2 (&backward[p->index], &tmp, &merged);
+            }
+
           /* Every element in the firstpos of the argument is in the follow
              of every element in the lastpos.  */
           {
diff --git a/support/intprops.h b/support/intprops.h
index 2c025688..cb086715 100644
--- a/support/intprops.h
+++ b/support/intprops.h
@@ -1,6 +1,6 @@
 /* intprops.h -- properties of integer types
 
-   Copyright (C) 2001-2019 Free Software Foundation, Inc.
+   Copyright (C) 2001-2020 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify it
    under the terms of the GNU Lesser General Public License as published
@@ -48,7 +48,7 @@
 /* Minimum and maximum values for integer types and expressions.  */
 
 /* The width in bits of the integer type or expression T.
-   Do not evaluate T.
+   Do not evaluate T.  T must not be a bit-field expression.
    Padding bits are not supported; this is checked at compile-time below.  */
 #define TYPE_WIDTH(t) (sizeof (t) * CHAR_BIT)
 
@@ -70,7 +70,7 @@
    ? _GL_SIGNED_INT_MAXIMUM (e)                                         \
    : _GL_INT_NEGATE_CONVERT (e, 1))
 #define _GL_SIGNED_INT_MAXIMUM(e)                                       \
-  (((_GL_INT_CONVERT (e, 1) << (TYPE_WIDTH ((e) + 0) - 2)) - 1) * 2 + 1)
+  (((_GL_INT_CONVERT (e, 1) << (TYPE_WIDTH (+ (e)) - 2)) - 1) * 2 + 1)
 
 /* Work around OpenVMS incompatibility with C99.  */
 #if !defined LLONG_MAX && defined __INT64_MAX
@@ -86,6 +86,7 @@
 /* Does the __typeof__ keyword work?  This could be done by
    'configure', but for now it's easier to do it by hand.  */
 #if (2 <= __GNUC__ \
+     || (4 <= __clang_major__) \
      || (1210 <= __IBMC__ && defined __IBM__TYPEOF__) \
      || (0x5110 <= __SUNPRO_C && !__STDC__))
 # define _GL_HAVE___TYPEOF__ 1
@@ -94,8 +95,9 @@
 #endif
 
 /* Return 1 if the integer type or expression T might be signed.  Return 0
-   if it is definitely unsigned.  This macro does not evaluate its argument,
-   and expands to an integer constant expression.  */
+   if it is definitely unsigned.  T must not be a bit-field expression.
+   This macro does not evaluate its argument, and expands to an
+   integer constant expression.  */
 #if _GL_HAVE___TYPEOF__
 # define _GL_SIGNED_TYPE_OR_EXPR(t) TYPE_SIGNED (__typeof__ (t))
 #else
@@ -108,6 +110,8 @@
 #define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485)
 
 /* Bound on length of the string representing an integer type or expression T.
+   T must not be a bit-field expression.
+
    Subtract 1 for the sign bit if T is signed, and then add 1 more for
    a minus sign if needed.
 
@@ -119,7 +123,7 @@
    + _GL_SIGNED_TYPE_OR_EXPR (t))
 
 /* Bound on buffer size needed to represent an integer type or expression T,
-   including the terminating null.  */
+   including the terminating null.  T must not be a bit-field expression.  */
 #define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1)
 
 
@@ -220,15 +224,33 @@
    ? (a) < (min) >> (b)                                 \
    : (max) >> (b) < (a))
 
-/* True if __builtin_add_overflow (A, B, P) works when P is non-null.  */
+/* True if __builtin_add_overflow (A, B, P) and __builtin_sub_overflow
+   (A, B, P) work when P is non-null.  */
 #if 5 <= __GNUC__ && !defined __ICC
-# define _GL_HAS_BUILTIN_OVERFLOW 1
+# define _GL_HAS_BUILTIN_ADD_OVERFLOW 1
+#elif defined __has_builtin
+# define _GL_HAS_BUILTIN_ADD_OVERFLOW __has_builtin (__builtin_add_overflow)
+#else
+# define _GL_HAS_BUILTIN_ADD_OVERFLOW 0
+#endif
+
+/* True if __builtin_mul_overflow (A, B, P) works when P is non-null.  */
+#ifdef __clang__
+/* Work around Clang bug <https://bugs.llvm.org/show_bug.cgi?id=16404>.  */
+# define _GL_HAS_BUILTIN_MUL_OVERFLOW 0
 #else
-# define _GL_HAS_BUILTIN_OVERFLOW 0
+# define _GL_HAS_BUILTIN_MUL_OVERFLOW _GL_HAS_BUILTIN_ADD_OVERFLOW
 #endif
 
-/* True if __builtin_add_overflow_p (A, B, C) works.  */
-#define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__)
+/* True if __builtin_add_overflow_p (A, B, C) works, and similarly for
+   __builtin_sub_overflow_p and __builtin_mul_overflow_p.  */
+#ifdef __clang__
+/* Clang 9 lacks __builtin_mul_overflow_p, and even if it did it would
+   presumably run afoul of Clang bug 16404.  */
+# define _GL_HAS_BUILTIN_OVERFLOW_P 0
+#else
+# define _GL_HAS_BUILTIN_OVERFLOW_P (7 <= __GNUC__)
+#endif
 
 /* The _GL*_OVERFLOW macros have the same restrictions as the
    *_RANGE_OVERFLOW macros, except that they do not assume that operands
@@ -351,43 +373,49 @@
 
 /* Store the low-order bits of A + B, A - B, A * B, respectively, into *R.
    Return 1 if the result overflows.  See above for restrictions.  */
-#define INT_ADD_WRAPV(a, b, r) \
-  _GL_INT_OP_WRAPV (a, b, r, +, __builtin_add_overflow, \
-                    _GL_INT_ADD_RANGE_OVERFLOW)
-#define INT_SUBTRACT_WRAPV(a, b, r) \
-  _GL_INT_OP_WRAPV (a, b, r, -, __builtin_sub_overflow, \
-                    _GL_INT_SUBTRACT_RANGE_OVERFLOW)
-#define INT_MULTIPLY_WRAPV(a, b, r) \
-   _GL_INT_OP_WRAPV (a, b, r, *, _GL_BUILTIN_MUL_OVERFLOW, \
-                     _GL_INT_MULTIPLY_RANGE_OVERFLOW)
-
-/* Like __builtin_mul_overflow, but work around GCC bug 91450.  */
-#define _GL_BUILTIN_MUL_OVERFLOW(a, b, r) \
-  ((!_GL_SIGNED_TYPE_OR_EXPR (*(r)) && EXPR_SIGNED (a) && EXPR_SIGNED (b) \
-    && _GL_INT_MULTIPLY_RANGE_OVERFLOW (a, b, 0, (__typeof__ (*(r))) -1)) \
-   ? ((void) __builtin_mul_overflow (a, b, r), 1) \
-   : __builtin_mul_overflow (a, b, r))
+#if _GL_HAS_BUILTIN_ADD_OVERFLOW
+# define INT_ADD_WRAPV(a, b, r) __builtin_add_overflow (a, b, r)
+# define INT_SUBTRACT_WRAPV(a, b, r) __builtin_sub_overflow (a, b, r)
+#else
+# define INT_ADD_WRAPV(a, b, r) \
+   _GL_INT_OP_WRAPV (a, b, r, +, _GL_INT_ADD_RANGE_OVERFLOW)
+# define INT_SUBTRACT_WRAPV(a, b, r) \
+   _GL_INT_OP_WRAPV (a, b, r, -, _GL_INT_SUBTRACT_RANGE_OVERFLOW)
+#endif
+#if _GL_HAS_BUILTIN_MUL_OVERFLOW
+# if (9 < __GNUC__ + (3 <= __GNUC_MINOR__) \
+      || (__GNUC__ == 8 && 4 <= __GNUC_MINOR__))
+#  define INT_MULTIPLY_WRAPV(a, b, r) __builtin_mul_overflow (a, b, r)
+# else
+   /* Work around GCC bug 91450.  */
+#  define INT_MULTIPLY_WRAPV(a, b, r) \
+    ((!_GL_SIGNED_TYPE_OR_EXPR (*(r)) && EXPR_SIGNED (a) && EXPR_SIGNED (b) \
+      && _GL_INT_MULTIPLY_RANGE_OVERFLOW (a, b, 0, (__typeof__ (*(r))) -1)) \
+     ? ((void) __builtin_mul_overflow (a, b, r), 1) \
+     : __builtin_mul_overflow (a, b, r))
+# endif
+#else
+# define INT_MULTIPLY_WRAPV(a, b, r) \
+   _GL_INT_OP_WRAPV (a, b, r, *, _GL_INT_MULTIPLY_RANGE_OVERFLOW)
+#endif
 
 /* Nonzero if this compiler has GCC bug 68193 or Clang bug 25390.  See:
    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68193
    https://llvm.org/bugs/show_bug.cgi?id=25390
    For now, assume all versions of GCC-like compilers generate bogus
-   warnings for _Generic.  This matters only for older compilers that
-   lack __builtin_add_overflow.  */
-#if __GNUC__
+   warnings for _Generic.  This matters only for compilers that
+   lack relevant builtins.  */
+#if __GNUC__ || defined __clang__
 # define _GL__GENERIC_BOGUS 1
 #else
 # define _GL__GENERIC_BOGUS 0
 #endif
 
 /* Store the low-order bits of A <op> B into *R, where OP specifies
-   the operation.  BUILTIN is the builtin operation, and OVERFLOW the
-   overflow predicate.  Return 1 if the result overflows.  See above
-   for restrictions.  */
-#if _GL_HAS_BUILTIN_OVERFLOW
-# define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) builtin (a, b, r)
-#elif 201112 <= __STDC_VERSION__ && !_GL__GENERIC_BOGUS
-# define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \
+   the operation and OVERFLOW the overflow predicate.  Return 1 if the
+   result overflows.  See above for restrictions.  */
+#if 201112 <= __STDC_VERSION__ && !_GL__GENERIC_BOGUS
+# define _GL_INT_OP_WRAPV(a, b, r, op, overflow) \
    (_Generic \
     (*(r), \
      signed char: \
@@ -442,7 +470,7 @@
         : (*(r) = _GL_INT_OP_WRAPV_VIA_UNSIGNED (a,b,op,unsigned,st), 0)))
 # endif
 
-# define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \
+# define _GL_INT_OP_WRAPV(a, b, r, op, overflow) \
    (sizeof *(r) == sizeof (signed char) \
     ? _GL_INT_OP_WRAPV_SMALLISH (a, b, r, op, overflow, \
                                  signed char, SCHAR_MIN, SCHAR_MAX, \
@@ -547,7 +575,7 @@
       ? (EXPR_SIGNED (_GL_INT_CONVERT (tmax, b)) \
          ? (a) < (tmax) / (b) \
          : ((INT_NEGATE_OVERFLOW (b) \
-             ? _GL_INT_CONVERT (b, tmax) >> (TYPE_WIDTH (b) - 1) \
+             ? _GL_INT_CONVERT (b, tmax) >> (TYPE_WIDTH (+ (b)) - 1) \
              : (tmax) / -(b)) \
             <= -1 - (a))) \
       : INT_NEGATE_OVERFLOW (_GL_INT_CONVERT (b, tmin)) && (b) == -1 \
diff --git a/support/regcomp.c b/support/regcomp.c
index 93bb0a05..692928b0 100644
--- a/support/regcomp.c
+++ b/support/regcomp.c
@@ -558,7 +558,7 @@ weak_alias (__regerror, regerror)
 static const bitset_t utf8_sb_map =
 {
   /* Set the first 128 bits.  */
-# if defined __GNUC__ && !defined __STRICT_ANSI__
+# if (defined __GNUC__ || __clang_major__ >= 4) && !defined __STRICT_ANSI__
   [0 ... 0x80 / BITSET_WORD_BITS - 1] = BITSET_WORD_MAX
 # else
 #  if 4 * BITSET_WORD_BITS < ASCII_CHARS
diff --git a/support/regex.h b/support/regex.h
index 87cce7f5..7418e6c7 100644
--- a/support/regex.h
+++ b/support/regex.h
@@ -600,11 +600,9 @@ extern void re_set_registers (struct re_pattern_buffer *__buffer,
 #endif	/* Use GNU */
 
 #if defined _REGEX_RE_COMP || (defined _LIBC && defined __USE_MISC)
-# ifndef _CRAY
 /* 4.2 bsd compatibility.  */
 extern char *re_comp (const char *);
 extern int re_exec (const char *);
-# endif
 #endif
 
 /* For plain 'restrict', use glibc's __restrict if defined.
@@ -614,7 +612,9 @@ extern int re_exec (const char *);
    'configure' might #define 'restrict' to those words, so pick a
    different name.  */
 #ifndef _Restrict_
-# if defined __restrict || 2 < __GNUC__ + (95 <= __GNUC_MINOR__)
+# if defined __restrict \
+     || 2 < __GNUC__ + (95 <= __GNUC_MINOR__) \
+     || __clang_major__ >= 3
 #  define _Restrict_ __restrict
 # elif 199901L <= __STDC_VERSION__ || defined restrict
 #  define _Restrict_ restrict
@@ -622,13 +622,18 @@ extern int re_exec (const char *);
 #  define _Restrict_
 # endif
 #endif
-/* For [restrict], use glibc's __restrict_arr if available.
-   Otherwise, GCC 3.1 (not in C++ mode) and C99 support [restrict].  */
+/* For the ISO C99 syntax
+     array_name[restrict]
+   use glibc's __restrict_arr if available.
+   Otherwise, GCC 3.1 and clang support this syntax (but not in C++ mode).
+   Other ISO C99 compilers support it as well.  */
 #ifndef _Restrict_arr_
 # ifdef __restrict_arr
 #  define _Restrict_arr_ __restrict_arr
-# elif ((199901L <= __STDC_VERSION__ || 3 < __GNUC__ + (1 <= __GNUC_MINOR__)) \
-        && !defined __GNUG__)
+# elif ((199901L <= __STDC_VERSION__ \
+         || 3 < __GNUC__ + (1 <= __GNUC_MINOR__) \
+         || __clang_major__ >= 3) \
+        && !defined __cplusplus)
 #  define _Restrict_arr_ _Restrict_
 # else
 #  define _Restrict_arr_
diff --git a/support/regex_internal.h b/support/regex_internal.h
index 8c42586c..dbc503cd 100644
--- a/support/regex_internal.h
+++ b/support/regex_internal.h
@@ -335,7 +335,7 @@ typedef struct
     Idx idx;			/* for BACK_REF */
     re_context_type ctx_type;	/* for ANCHOR */
   } opr;
-#if __GNUC__ >= 2 && !defined __STRICT_ANSI__
+#if (__GNUC__ >= 2 || defined __clang__) && !defined __STRICT_ANSI__
   re_token_type_t type : 8;
 #else
   re_token_type_t type;
@@ -841,10 +841,10 @@ re_string_elem_size_at (const re_string_t *pstr, Idx idx)
 #endif /* RE_ENABLE_I18N */
 
 #ifndef FALLTHROUGH
-# if __GNUC__ < 7
-#  define FALLTHROUGH ((void) 0)
-# else
+# if (__GNUC__ >= 7) || (__clang_major__ >= 10)
 #  define FALLTHROUGH __attribute__ ((__fallthrough__))
+# else
+#  define FALLTHROUGH ((void) 0)
 # endif
 #endif
 
diff --git a/support/verify.h b/support/verify.h
index f1097612..fa1ed717 100644
--- a/support/verify.h
+++ b/support/verify.h
@@ -23,11 +23,15 @@
 
 /* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert (R, DIAGNOSTIC)
    works as per C11.  This is supported by GCC 4.6.0 and later, in C
-   mode.
+   mode, and by clang (also in C++ mode).
 
    Define _GL_HAVE__STATIC_ASSERT1 to 1 if _Static_assert (R) works as
-   per C2X, and define _GL_HAVE_STATIC_ASSERT1 if static_assert (R)
-   works as per C++17.  This is supported by GCC 9.1 and later.
+   per C2X.  This is supported by GCC 9.1 and later, and by clang in
+   C++1z mode.
+
+   Define _GL_HAVE_STATIC_ASSERT1 if static_assert (R) works as per
+   C++17.  This is supported by GCC 9.1 and later, and by clang in
+   C++1z mode.
 
    Support compilers claiming conformance to the relevant standard,
    and also support GCC when not pedantic.  If we were willing to slow
@@ -35,7 +39,8 @@
    since this affects only the quality of diagnostics, why bother?  */
 #ifndef __cplusplus
 # if (201112L <= __STDC_VERSION__ \
-      || (!defined __STRICT_ANSI__ && 4 < __GNUC__ + (6 <= __GNUC_MINOR__)))
+      || (!defined __STRICT_ANSI__ \
+          && (4 < __GNUC__ + (6 <= __GNUC_MINOR__) || 4 <= __clang_major__)))
 #  define _GL_HAVE__STATIC_ASSERT 1
 # endif
 # if (202000L <= __STDC_VERSION__ \
@@ -43,7 +48,15 @@
 #  define _GL_HAVE__STATIC_ASSERT1 1
 # endif
 #else
-# if 201703L <= __cplusplus || 9 <= __GNUC__
+# if 4 <= __clang_major__
+#  define _GL_HAVE__STATIC_ASSERT 1
+# endif
+# if 4 <= __clang_major__ && 201411 <= __cpp_static_assert
+#  define _GL_HAVE__STATIC_ASSERT1 1
+# endif
+# if 201703L <= __cplusplus \
+     || 9 <= __GNUC__ \
+     || (4 <= __clang_major__ && 201411 <= __cpp_static_assert)
 #  define _GL_HAVE_STATIC_ASSERT1 1
 # endif
 #endif
@@ -292,7 +305,12 @@ template <int w>
 
    Although assuming R can help a compiler generate better code or
    diagnostics, performance can suffer if R uses hard-to-optimize
-   features such as function calls not inlined by the compiler.  */
+   features such as function calls not inlined by the compiler.
+
+   Avoid Clang's __builtin_assume, as it breaks GNU Emacs master
+   as of 2020-08-23T21:09:49Z!eggert@cs.ucla.edu; see
+   <https://bugs.gnu.org/43152#71>.  It's not known whether this breakage
+   is a Clang bug or an Emacs bug; play it safe for now.  */
 
 #if _GL_HAS_BUILTIN_UNREACHABLE
 # define assume(R) ((R) ? (void) 0 : __builtin_unreachable ())