[RFC 1/2] Change how the symbol_version_reference macro is defined

[Adhemerval Zanella]

On 18/03/2021 17:07, Florian Weimer via Libc-alpha wrote:
> A subsequent change will require including <config.h> for defining
> symbol_version_reference.  <libc-symbol.h> should not include
> <config.h> for _ISOMAC, so it cannot define symbol_version_reference
> anymore, but symbol_version_reference is needed <shlib-compat.h> even
> for _ISOMAC.  Moving the definition of symbol_version_reference to a
> separate file <libc-symver.h> makes it possible to use a single
> definition for both cases.

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  include/libc-symbols.h | 16 +++-------------
>  include/libc-symver.h  | 38 ++++++++++++++++++++++++++++++++++++++
>  include/shlib-compat.h |  3 +++
>  3 files changed, 44 insertions(+), 13 deletions(-)
>  create mode 100644 include/libc-symver.h
> 
> diff --git a/include/libc-symbols.h b/include/libc-symbols.h
> index c83e550b03..ce5f75a1a2 100644
> --- a/include/libc-symbols.h
> +++ b/include/libc-symbols.h
> @@ -59,19 +59,6 @@
>  # define IN_MODULE (-1)
>  #endif
>  
> -/* Use symbol_version_reference to specify the version a symbol
> -   reference should link to.  Use symbol_version or
> -   default_symbol_version for the definition of a versioned symbol.
> -   The difference is that the latter is a no-op in non-shared
> -   builds.  */
> -#ifdef __ASSEMBLER__
> -# define symbol_version_reference(real, name, version) \
> -     .symver real, name##@##version
> -#else  /* !__ASSEMBLER__ */
> -# define symbol_version_reference(real, name, version) \
> -  __asm__ (".symver " #real "," #name "@" #version)
> -#endif
> -
>  #ifndef _ISOMAC
>  
>  /* This is defined for the compilation of all C library code.  features.h

Ok.

> @@ -97,6 +84,9 @@
>  
>  #include <config.h>
>  
> +/* Obtain the definition of symbol_version_reference.  */
> +#include <libc-symver.h>
> +
>  /* When PIC is defined and SHARED isn't defined, we are building PIE
>     by default.  */
>  #if defined PIC && !defined SHARED

Ok.

> diff --git a/include/libc-symver.h b/include/libc-symver.h
> new file mode 100644
> index 0000000000..11c77ae1cd
> --- /dev/null
> +++ b/include/libc-symver.h
> @@ -0,0 +1,38 @@
> +/* Symbol version management.
> +   Copyright (C) 1995-2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +/* This file is included from <libc-symbols.h> for !_ISOMAC, and
> +   unconditionally from <shlib-compat.h>.  */
> +
> +#ifndef _LIBC_SYMVER_H
> +#define _LIBC_SYMVER_H 1
> +
> +/* Use symbol_version_reference to specify the version a symbol
> +   reference should link to.  Use symbol_version or
> +   default_symbol_version for the definition of a versioned symbol.
> +   The difference is that the latter is a no-op in non-shared
> +   builds.  */
> +#ifdef __ASSEMBLER__
> +# define symbol_version_reference(real, name, version) \
> +     .symver real, name##@##version
> +#else  /* !__ASSEMBLER__ */
> +# define symbol_version_reference(real, name, version) \
> +  __asm__ (".symver " #real "," #name "@" #version)
> +#endif
> +
> +#endif /* _LIBC_SYMVER_H */

Ok.

> diff --git a/include/shlib-compat.h b/include/shlib-compat.h
> index 28baef1ea4..b874e2588f 100644
> --- a/include/shlib-compat.h
> +++ b/include/shlib-compat.h
> @@ -21,6 +21,9 @@
>  
>  # include <abi-versions.h>
>  
> +/* Obtain the definition of symbol_version_reference.  */
> +#include <libc-symver.h>
> +
>  /* The file abi-versions.h (generated by scripts/abi-versions.awk) defines
>     symbols like `ABI_libm_GLIBC_2_0' for each version set in the source
>     code for each library.  For a version set that is subsumed by a later
> 

Ok.