Add support for GCC 9 attribute copy.

GCC 9 has gained an enhancement to help detect attribute mismatches
between alias declarations and their targets.  It consists of a new
warning, -Wattribute-alias, an enhancement to an existing warning,
-Wmissing-attributes, and a new attribute called copy.

The purpose of the warnings is to help identify either possible bugs
(an alias declared with more restrictive attributes than its target
promises) or optimization or diagnostic opportunities (an alias target
missing some attributes that it could be declared with that might
benefit analysis and code generation).  The purpose of the new
attribute is to easily apply (almost) the same set of attributes
to one declaration as those already present on another.

As expected (and intended) the enhancement triggers warnings for
many alias declarations in Glibc code.  This change, tested on
x86_64-linux, avoids all instances of the new warnings by making
use of the attribute where appropriate.  To fully benefit from
the enhancement Glibc will need to be compiled with
 -Wattribute-alias=2 and remaining warnings reviewed and dealt with
(there are a couple of thousand but most should be straightforward
to deal with).

ChangeLog:

	* include/libc-symbols.h (__attribute_copy__): Define macro unless
	it's already defined.
	(_strong_alias): Use __attribute_copy__.
	(_weak_alias,  __hidden_ver1,  __hidden_nolink2): Same.
	* misc/sys/cdefs.h (__attribute_copy__): New macro.
	* sysdeps/x86_64/multiarch/memchr.c (memchr): Use __attribute_copy__.
	* sysdeps/x86_64/multiarch/memcmp.c (memcmp): Same.
	* sysdeps/x86_64/multiarch/mempcpy.c (mempcpy): Same.
	* sysdeps/x86_64/multiarch/memset.c (memset): Same.
	* sysdeps/x86_64/multiarch/stpcpy.c (stpcpy): Same.
	* sysdeps/x86_64/multiarch/strcat.c (strcat): Same.
	* sysdeps/x86_64/multiarch/strchr.c (strchr): Same.
	* sysdeps/x86_64/multiarch/strcmp.c (strcmp): Same.
	* sysdeps/x86_64/multiarch/strcpy.c (strcpy): Same.
	* sysdeps/x86_64/multiarch/strcspn.c (strcspn): Same.
	* sysdeps/x86_64/multiarch/strlen.c (strlen): Same.
	* sysdeps/x86_64/multiarch/strncmp.c (strncmp): Same.
	* sysdeps/x86_64/multiarch/strncpy.c (strncpy): Same.
	* sysdeps/x86_64/multiarch/strnlen.c (strnlen): Same.
	* sysdeps/x86_64/multiarch/strpbrk.c (strpbrk): Same.
	* sysdeps/x86_64/multiarch/strrchr.c (strrchr): Same.
	* sysdeps/x86_64/multiarch/strspn.c (strspn): Same.

21 files changed, 71 insertions, 26 deletions

diff --git a/ChangeLog b/ChangeLog
index 7d723f5..e43fd3e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,28 @@
+2018-11-09  Martin Sebor  <msebor@redhat.com>
+
+	* include/libc-symbols.h (__attribute_copy__): Define macro unless
+	it's already defined.
+	(_strong_alias): Use __attribute_copy__.
+	(_weak_alias,  __hidden_ver1,  __hidden_nolink2): Same.
+	* misc/sys/cdefs.h (__attribute_copy__): New macro.
+	* sysdeps/x86_64/multiarch/memchr.c (memchr): Use __attribute_copy__.
+	* sysdeps/x86_64/multiarch/memcmp.c (memcmp): Same.
+	* sysdeps/x86_64/multiarch/mempcpy.c (mempcpy): Same.
+	* sysdeps/x86_64/multiarch/memset.c (memset): Same.
+	* sysdeps/x86_64/multiarch/stpcpy.c (stpcpy): Same.
+	* sysdeps/x86_64/multiarch/strcat.c (strcat): Same.
+	* sysdeps/x86_64/multiarch/strchr.c (strchr): Same.
+	* sysdeps/x86_64/multiarch/strcmp.c (strcmp): Same.
+	* sysdeps/x86_64/multiarch/strcpy.c (strcpy): Same.
+	* sysdeps/x86_64/multiarch/strcspn.c (strcspn): Same.
+	* sysdeps/x86_64/multiarch/strlen.c (strlen): Same.
+	* sysdeps/x86_64/multiarch/strncmp.c (strncmp): Same.
+	* sysdeps/x86_64/multiarch/strncpy.c (strncpy): Same.
+	* sysdeps/x86_64/multiarch/strnlen.c (strnlen): Same.
+	* sysdeps/x86_64/multiarch/strpbrk.c (strpbrk): Same.
+	* sysdeps/x86_64/multiarch/strrchr.c (strrchr): Same.
+	* sysdeps/x86_64/multiarch/strspn.c (strspn): Same.
+
 2018-11-09  Gabriel F. T. Gomes  <gabriel@inconstante.eti.br>
 
 	* misc/tst-efgcvt.c: Include support/check.h and
diff --git a/include/libc-symbols.h b/include/libc-symbols.h
index 8b9273c..e71a479 100644
--- a/include/libc-symbols.h
+++ b/include/libc-symbols.h
@@ -125,6 +125,11 @@
 # define ASM_LINE_SEP ;
 #endif
 
+#ifndef __attribute_copy__
+/* Provide an empty definition when cdefs.h is not included.  */
+# define __attribute_copy__(arg)
+#endif
+
 #ifndef __ASSEMBLER__
 /* GCC understands weak symbols and aliases; use its interface where
    possible, instead of embedded assembly language.  */
@@ -132,7 +137,8 @@
 /* Define ALIASNAME as a strong alias for NAME.  */
 # define strong_alias(name, aliasname) _strong_alias(name, aliasname)
 # define _strong_alias(name, aliasname) \
-  extern __typeof (name) aliasname __attribute__ ((alias (#name)));
+  extern __typeof (name) aliasname __attribute__ ((alias (#name))) \
+    __attribute_copy__ (name);
 
 /* This comes between the return type and function name in
    a function definition to make that definition weak.  */
@@ -143,14 +149,16 @@
    If weak aliases are not available, this defines a strong alias.  */
 # define weak_alias(name, aliasname) _weak_alias (name, aliasname)
 # define _weak_alias(name, aliasname) \
-  extern __typeof (name) aliasname __attribute__ ((weak, alias (#name)));
+  extern __typeof (name) aliasname __attribute__ ((weak, alias (#name))) \
+    __attribute_copy__ (name);
 
 /* Same as WEAK_ALIAS, but mark symbol as hidden.  */
 # define weak_hidden_alias(name, aliasname) \
   _weak_hidden_alias (name, aliasname)
 # define _weak_hidden_alias(name, aliasname) \
   extern __typeof (name) aliasname \
-    __attribute__ ((weak, alias (#name), __visibility__ ("hidden")));
+    __attribute__ ((weak, alias (#name), __visibility__ ("hidden"))) \
+    __attribute_copy__ (name);
 
 /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined).  */
 # define weak_extern(symbol) _weak_extern (weak symbol)
@@ -532,7 +540,8 @@ for linking")
 #  define __hidden_ver1(local, internal, name) \
   extern __typeof (name) __EI_##name __asm__(__hidden_asmname (#internal)); \
   extern __typeof (name) __EI_##name \
-	__attribute__((alias (__hidden_asmname (#local))))
+    __attribute__((alias (__hidden_asmname (#local))))	\
+    __attribute_copy__ (name)
 #  define hidden_ver(local, name)	__hidden_ver1(local, __GI_##name, name);
 #  define hidden_data_ver(local, name)	hidden_ver(local, name)
 #  define hidden_def(name)		__hidden_ver1(__GI_##name, name, name);
@@ -545,7 +554,8 @@ for linking")
 #  define __hidden_nolink1(local, internal, name, version) \
   __hidden_nolink2 (local, internal, name, version)
 #  define __hidden_nolink2(local, internal, name, version) \
-  extern __typeof (name) internal __attribute__ ((alias (#local))); \
+  extern __typeof (name) internal __attribute__ ((alias (#local)))	\
+    __attribute_copy__ (name);						\
   __hidden_nolink3 (local, internal, #name "@" #version)
 #  define __hidden_nolink3(local, internal, vername) \
   __asm__ (".symver " #internal ", " vername);
diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
index 3f6fe3c..8d58568 100644
--- a/misc/sys/cdefs.h
+++ b/misc/sys/cdefs.h
@@ -431,6 +431,16 @@
 # define __attribute_nonstring__
 #endif
 
+/* Undefine (also defined in libc-symbols.h).  */
+#undef __attribute_copy__
+#if __GNUC_PREREQ (9, 0)
+/* Copies attributes from the declaration or type referenced by
+   the argument.  */
+# define __attribute_copy__(arg) __attribute__ ((__copy__ (arg)))
+#else
+# define __attribute_copy__(arg)
+#endif
+
 #if (!defined _Static_assert && !defined __cplusplus \
      && (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) < 201112 \
      && (!__GNUC_PREREQ (4, 6) || defined __STRICT_ANSI__))
diff --git a/sysdeps/x86_64/multiarch/memchr.c b/sysdeps/x86_64/multiarch/memchr.c
index 016f578..372dd77 100644
--- a/sysdeps/x86_64/multiarch/memchr.c
+++ b/sysdeps/x86_64/multiarch/memchr.c
@@ -30,6 +30,6 @@ libc_ifunc_redirected (__redirect_memchr, memchr, IFUNC_SELECTOR ());
 strong_alias (memchr, __memchr)
 # ifdef SHARED
 __hidden_ver1 (memchr, __GI_memchr, __redirect_memchr)
-  __attribute__((visibility ("hidden")));
+  __attribute__((visibility ("hidden"))) __attribute_copy__ (memchr);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/memcmp.c b/sysdeps/x86_64/multiarch/memcmp.c
index 6f3ca43..bbd3b01 100644
--- a/sysdeps/x86_64/multiarch/memcmp.c
+++ b/sysdeps/x86_64/multiarch/memcmp.c
@@ -32,6 +32,6 @@ weak_alias (memcmp, bcmp)
 
 # ifdef SHARED
 __hidden_ver1 (memcmp, __GI_memcmp, __redirect_memcmp)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (memcmp);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/mempcpy.c b/sysdeps/x86_64/multiarch/mempcpy.c
index 9fe41dd..d2f7928 100644
--- a/sysdeps/x86_64/multiarch/mempcpy.c
+++ b/sysdeps/x86_64/multiarch/mempcpy.c
@@ -35,8 +35,8 @@ libc_ifunc_redirected (__redirect_mempcpy, __mempcpy, IFUNC_SELECTOR ());
 weak_alias (__mempcpy, mempcpy)
 # ifdef SHARED
 __hidden_ver1 (__mempcpy, __GI___mempcpy, __redirect___mempcpy)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (mempcpy);
 __hidden_ver1 (mempcpy, __GI_mempcpy, __redirect_mempcpy)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (mempcpy);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/memset.c b/sysdeps/x86_64/multiarch/memset.c
index 064841d..4b8f57f 100644
--- a/sysdeps/x86_64/multiarch/memset.c
+++ b/sysdeps/x86_64/multiarch/memset.c
@@ -30,6 +30,6 @@ libc_ifunc_redirected (__redirect_memset, memset, IFUNC_SELECTOR ());
 
 # ifdef SHARED
 __hidden_ver1 (memset, __GI_memset, __redirect_memset)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (memset);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/stpcpy.c b/sysdeps/x86_64/multiarch/stpcpy.c
index 1e340fc..f74a54b 100644
--- a/sysdeps/x86_64/multiarch/stpcpy.c
+++ b/sysdeps/x86_64/multiarch/stpcpy.c
@@ -35,8 +35,8 @@ libc_ifunc_redirected (__redirect_stpcpy, __stpcpy, IFUNC_SELECTOR ());
 weak_alias (__stpcpy, stpcpy)
 # ifdef SHARED
 __hidden_ver1 (__stpcpy, __GI___stpcpy, __redirect___stpcpy)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (stpcpy);
 __hidden_ver1 (stpcpy, __GI_stpcpy, __redirect_stpcpy)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (stpcpy);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strcat.c b/sysdeps/x86_64/multiarch/strcat.c
index 1f7f626..1922c0a 100644
--- a/sysdeps/x86_64/multiarch/strcat.c
+++ b/sysdeps/x86_64/multiarch/strcat.c
@@ -30,6 +30,6 @@ libc_ifunc_redirected (__redirect_strcat, strcat, IFUNC_SELECTOR ());
 
 # ifdef SHARED
 __hidden_ver1 (strcat, __GI_strcat, __redirect_strcat)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strcat);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strchr.c b/sysdeps/x86_64/multiarch/strchr.c
index 76d64fb..87e99ba 100644
--- a/sysdeps/x86_64/multiarch/strchr.c
+++ b/sysdeps/x86_64/multiarch/strchr.c
@@ -50,6 +50,6 @@ libc_ifunc_redirected (__redirect_strchr, strchr, IFUNC_SELECTOR ());
 weak_alias (strchr, index)
 # ifdef SHARED
 __hidden_ver1 (strchr, __GI_strchr, __redirect_strchr)
-  __attribute__((visibility ("hidden")));
+  __attribute__((visibility ("hidden"))) __attribute_copy__ (strchr);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strcmp.c b/sysdeps/x86_64/multiarch/strcmp.c
index b903e41..e3cf39d 100644
--- a/sysdeps/x86_64/multiarch/strcmp.c
+++ b/sysdeps/x86_64/multiarch/strcmp.c
@@ -54,6 +54,6 @@ libc_ifunc_redirected (__redirect_strcmp, strcmp, IFUNC_SELECTOR ());
 
 # ifdef SHARED
 __hidden_ver1 (strcmp, __GI_strcmp, __redirect_strcmp)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strcmp);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strcpy.c b/sysdeps/x86_64/multiarch/strcpy.c
index 12e0e3f..ce819dd 100644
--- a/sysdeps/x86_64/multiarch/strcpy.c
+++ b/sysdeps/x86_64/multiarch/strcpy.c
@@ -30,6 +30,6 @@ libc_ifunc_redirected (__redirect_strcpy, strcpy, IFUNC_SELECTOR ());
 
 # ifdef SHARED
 __hidden_ver1 (strcpy, __GI_strcpy, __redirect_strcpy)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strcpy);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strcspn.c b/sysdeps/x86_64/multiarch/strcspn.c
index 9712e84..9d96526 100644
--- a/sysdeps/x86_64/multiarch/strcspn.c
+++ b/sysdeps/x86_64/multiarch/strcspn.c
@@ -30,6 +30,6 @@ libc_ifunc_redirected (__redirect_strcspn, strcspn, IFUNC_SELECTOR ());
 
 # ifdef SHARED
 __hidden_ver1 (strcspn, __GI_strcspn, __redirect_strcspn)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strcspn);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strlen.c b/sysdeps/x86_64/multiarch/strlen.c
index 1758d22..a230740 100644
--- a/sysdeps/x86_64/multiarch/strlen.c
+++ b/sysdeps/x86_64/multiarch/strlen.c
@@ -29,6 +29,6 @@
 libc_ifunc_redirected (__redirect_strlen, strlen, IFUNC_SELECTOR ());
 # ifdef SHARED
 __hidden_ver1 (strlen, __GI_strlen, __redirect_strlen)
-  __attribute__((visibility ("hidden")));
+  __attribute__((visibility ("hidden"))) __attribute_copy__ (strlen);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strncat.c b/sysdeps/x86_64/multiarch/strncat.c
index 841c165..2546277 100644
--- a/sysdeps/x86_64/multiarch/strncat.c
+++ b/sysdeps/x86_64/multiarch/strncat.c
@@ -30,6 +30,6 @@ libc_ifunc_redirected (__redirect_strncat, strncat, IFUNC_SELECTOR ());
 strong_alias (strncat, __strncat);
 # ifdef SHARED
 __hidden_ver1 (strncat, __GI___strncat, __redirect_strncat)
-  __attribute__((visibility ("hidden")));
+  __attribute__((visibility ("hidden"))) __attribute_copy__ (strncat);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strncmp.c b/sysdeps/x86_64/multiarch/strncmp.c
index 02b6d0b..32f5c6c 100644
--- a/sysdeps/x86_64/multiarch/strncmp.c
+++ b/sysdeps/x86_64/multiarch/strncmp.c
@@ -55,6 +55,6 @@ libc_ifunc_redirected (__redirect_strncmp, strncmp, IFUNC_SELECTOR ());
 
 # ifdef SHARED
 __hidden_ver1 (strncmp, __GI_strncmp, __redirect_strncmp)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strncmp);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strncpy.c b/sysdeps/x86_64/multiarch/strncpy.c
index 3c3de8b..37aae2c 100644
--- a/sysdeps/x86_64/multiarch/strncpy.c
+++ b/sysdeps/x86_64/multiarch/strncpy.c
@@ -30,6 +30,6 @@ libc_ifunc_redirected (__redirect_strncpy, strncpy, IFUNC_SELECTOR ());
 
 # ifdef SHARED
 __hidden_ver1 (strncpy, __GI_strncpy, __redirect_strncpy)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strncpy);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strnlen.c b/sysdeps/x86_64/multiarch/strnlen.c
index 3ab94ce..9d64335 100644
--- a/sysdeps/x86_64/multiarch/strnlen.c
+++ b/sysdeps/x86_64/multiarch/strnlen.c
@@ -32,8 +32,8 @@ libc_ifunc_redirected (__redirect_strnlen, __strnlen, IFUNC_SELECTOR ());
 weak_alias (__strnlen, strnlen);
 # ifdef SHARED
 __hidden_ver1 (__strnlen, __GI___strnlen, __redirect___strnlen)
-  __attribute__((visibility ("hidden")));
+  __attribute__((visibility ("hidden"))) __attribute_copy__ (strnlen);
 __hidden_ver1 (strnlen, __GI_strnlen, __redirect_strnlen)
-  __attribute__((weak, visibility ("hidden")));
+  __attribute__((weak, visibility ("hidden"))) __attribute_copy__ (strnlen);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strpbrk.c b/sysdeps/x86_64/multiarch/strpbrk.c
index a0d435a..f110367 100644
--- a/sysdeps/x86_64/multiarch/strpbrk.c
+++ b/sysdeps/x86_64/multiarch/strpbrk.c
@@ -30,6 +30,6 @@ libc_ifunc_redirected (__redirect_strpbrk, strpbrk, IFUNC_SELECTOR ());
 
 # ifdef SHARED
 __hidden_ver1 (strpbrk, __GI_strpbrk, __redirect_strpbrk)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strpbrk);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strrchr.c b/sysdeps/x86_64/multiarch/strrchr.c
index a719edd..ba7458a 100644
--- a/sysdeps/x86_64/multiarch/strrchr.c
+++ b/sysdeps/x86_64/multiarch/strrchr.c
@@ -29,6 +29,6 @@ libc_ifunc_redirected (__redirect_strrchr, strrchr, IFUNC_SELECTOR ());
 weak_alias (strrchr, rindex);
 # ifdef SHARED
 __hidden_ver1 (strrchr, __GI_strrchr, __redirect_strrchr)
-  __attribute__((visibility ("hidden")));
+  __attribute__((visibility ("hidden"))) __attribute_copy__ (strrchr);
 # endif
 #endif
diff --git a/sysdeps/x86_64/multiarch/strspn.c b/sysdeps/x86_64/multiarch/strspn.c
index 56ab4d9..5b9654e 100644
--- a/sysdeps/x86_64/multiarch/strspn.c
+++ b/sysdeps/x86_64/multiarch/strspn.c
@@ -30,6 +30,6 @@ libc_ifunc_redirected (__redirect_strspn, strspn, IFUNC_SELECTOR ());
 
 # ifdef SHARED
 __hidden_ver1 (strspn, __GI_strspn, __redirect_strspn)
-  __attribute__ ((visibility ("hidden")));
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strspn);
 # endif
 #endif