From 3e0c7985c9535304d87af3ad728f5f6d34557f0d Mon Sep 17 00:00:00 2001 From: Martin Sebor Date: Fri, 9 Nov 2018 17:24:12 -0700 Subject: [PATCH] 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. Using glibc arc-2.29-2019.02.08 or the upcoming arc-2019.03 release include this patch. [1] https://sourceware.org/git/?p=glibc.git;a=commit;h=1626a1cfcd6ba1cc64721be1036c2873211d499b [2] https://gitlab.com/kubu93/toolchains-builder/-/jobs/205435682 Signed-off-by: Romain Naour [Romain: - Backport from upstream [1] to fix build issue with glibc arc-2018.09-release (based on glibc 2.28) and gcc 9.1 [2] - Also drop the x86-64 related hunks to avoid confusion. ] Cc: Alexey Brodkin Cc: Evgeniy Didin Cc: Eugeniy Paltsev --- include/libc-symbols.h | 20 +++++++++++++++----- misc/sys/cdefs.h | 10 ++++++++++ 2 files changed, 25 insertions(+), 5 deletions(-) diff --git a/include/libc-symbols.h b/include/libc-symbols.h index 4548e09..ff99728 100644 --- a/include/libc-symbols.h +++ b/include/libc-symbols.h @@ -90,6 +90,11 @@ # 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. */ @@ -97,7 +102,8 @@ /* 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. */ @@ -108,14 +114,16 @@ 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) @@ -406,7 +414,8 @@ 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); @@ -419,7 +428,8 @@ 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 a3c2429..73bc603 100644 --- a/misc/sys/cdefs.h +++ b/misc/sys/cdefs.h @@ -404,6 +404,16 @@ # endif #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__)) -- 2.17.1