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.

1 files changed, 57 insertions, 31 deletions

diff --git a/lib/cdefs.h b/lib/cdefs.h
index f6c447ad377..beedd891fb8 100644
--- a/lib/cdefs.h
+++ b/lib/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.  */
@@ -51,7 +78,8 @@
    gcc 2.8.x and egcs.  For gcc 3.2 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, 3) || __glibc_clang_has_attribute (__nothrow__))
 #  define __THROW	__attribute__ ((__nothrow__ __LEAF))
 #  define __THROWNL	__attribute__ ((__nothrow__))
 #  define __NTH(fct)	__attribute__ ((__nothrow__ __LEAF)) fct
@@ -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 +148,12 @@
 # define __warnattr(msg) __attribute__((__warning__ (msg)))
 # define __errordecl(name, msg) \
   extern void name (void) __attribute__((__error__ (msg)))
+#elif __glibc_clang_has_attribute (__diagnose_if__)
+# 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)
@@ -194,17 +219,17 @@
 */
 #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 +247,14 @@
 /* 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 +263,7 @@
 /* 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 +272,7 @@
 #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 +295,7 @@
    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 +305,7 @@
    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 +316,7 @@
    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 +325,7 @@
 
 /* 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 +339,7 @@
 #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 +352,7 @@
 
 /* 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 */
@@ -370,7 +395,7 @@
    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
 
@@ -401,7 +426,7 @@
 # endif
 #endif
 
-#if (__GNUC__ >= 3) || (__clang_major__ >= 4)
+#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 +442,8 @@
 
 #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