[dpdk-dev] [PATCHv3 2/3] rte_compat: Add MAP_STATIC_SYMBOL macro

[Gajdzica, MaciejX T]

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Neil Horman
> Sent: Thursday, June 25, 2015 4:36 PM
> To: dev at dpdk.org
> Subject: [dpdk-dev] [PATCHv3 2/3] rte_compat: Add MAP_STATIC_SYMBOL
> macro
> 
> It was pointed out in my examples that doing shared library symbol versioning by
> partitioning symbols to version specific functions (as opposed to leaving the
> latest symol version at the base symbol name), neglects to take into account
> static builds.  Add a macro to handle that.  If you choose a versioning approach
> that uniquely names every version of the symbol, then this macro lets you map
> your symbol choice to the base name when building a static library
> 
> Also, while I'm at it, since we're documenting this in the guide, take the
> abbreviated example out of the header
> 
> Signed-off-by: Neil Horman <nhorman at tuxdriver.com>
> CC: thomas.monjalon at 6wind.com

Acked-by: Maciej Gajdzica <maciejx.t.gajdzica at intel.com>

> ---
>  lib/librte_compat/rte_compat.h | 35 ++++++++++++++++++-----------------
>  1 file changed, 18 insertions(+), 17 deletions(-)
> 
> diff --git a/lib/librte_compat/rte_compat.h b/lib/librte_compat/rte_compat.h
> index 75920a1..d7768d5 100644
> --- a/lib/librte_compat/rte_compat.h
> +++ b/lib/librte_compat/rte_compat.h
> @@ -49,22 +49,8 @@
>   * Assumptions: DPDK 2.(X) contains a function int foo(char *string)
>   *              DPDK 2.(X+1) needs to change foo to be int foo(int index)
>   *
> - * To accomplish this:
> - * 1) Edit lib/<library>/library_version.map to add a DPDK_2.(X+1) node, in
> which
> - * foo is exported as a global symbol.
> - *
> - * 2) rename the existing function int foo(char *string) to
> - *	int foo_v20(char *string)
> - *
> - * 3) Add this macro immediately below the function
> - *	VERSION_SYMBOL(foo, _v20, 2.0);
> - *
> - * 4) Implement a new version of foo.
> - *	char foo(int value, int otherval) { ...}
> - *
> - * 5) Mark the newest version as the default version
> - *	BIND_DEFAULT_SYMBOL(foo, _v21, 2.1);
> - *
> + * Refer to the guidelines document in the docs subdirectory for
> + details on the
> + * use of these macros
>   */
> 
>  /*
> @@ -72,6 +58,8 @@
>   * b - function base name
>   * e - function version extension, to be concatenated with base name
>   * n - function symbol version string to be applied
> + * f - function prototype
> + * p - full function symbol name
>   */
> 
>  /*
> @@ -96,6 +84,19 @@
>  #define BIND_DEFAULT_SYMBOL(b, e, n) __asm__(".symver " RTE_STR(b)
> RTE_STR(e) ", " RTE_STR(b) "@@DPDK_" RTE_STR(n))  #define __vsym
> __attribute__((used))
> 
> +/*
> + * MAP_STATIC_SYMBOL
> + * If a function has been bifurcated into multiple versions, none of
> +which
> + * are defined as the exported symbol name in the map file, this macro
> +can be
> + * used to alias a specific version of the symbol to its exported name.
> +For
> + * example, if you have 2 versions of a function foo_v1 and foo_v2,
> +where the
> + * former is mapped to foo at DPDK_1 and the latter is mapped to
> +foo at DPDK_2 when
> + * building a shared library, this macro can be used to map either
> +foo_v1 or
> + * foo_v2 to the symbol foo when building a static library, e.g.:
> + * MAP_STATIC_SYMBOL(void foo(), foo_v2);  */ #define
> +MAP_STATIC_SYMBOL(f, p)
> +
>  #else
>  /*
>   * No symbol versioning in use
> @@ -104,7 +105,7 @@
>  #define __vsym
>  #define BASE_SYMBOL(b, n)
>  #define BIND_DEFAULT_SYMBOL(b, e, n)
> -
> +#define MAP_STATIC_SYMBOL(f, p) f  __attribute__((alias( RTE_STR(p))))
>  /*
>   * RTE_BUILD_SHARED_LIB=n
>   */
> --
> 2.1.0