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[PATCH, V2 05/14] libsframe: implement an internal-only SFrame FDE representation

Jens Remus jremus@linux.ibm.com
Tue Dec 16 12:15:38 GMT 2025 
On 12/9/2025 9:59 AM, Indu Bhagat via Binutils wrote:
> Up until now, libsframe has used the same SFrame FDE representation as
> the on-disk representation (sframe_func_desc_entry).  The choice made by
> the author of the libary, back when it was first contributed, perhaps
> sufficed the needs then.  But looking forward, we need to be able to
> allow reading and dumping out of not just sections with version
> SFRAME_VERSION_2 but also future supported versions.
> 
> Note that libsframe did not expose the SFrame FDE representation in any
> public APIs;  doing so is not recommended.
> 
> For the path forward, create an internal-only SFrame FDE representation
> (sframe_func_desc_entry_int).  libsframe now keeps all in-memory FDEs of
> type sframe_func_desc_entry_int.  Doing so means instead of memcpy, we
> need to resort to member-by-member mapping.  This can be seen in
> sframe_fde_tbl_init (read time) and the new function
> sframe_encoder_write_fde (write time).
> 
> Other than that, replace out the previous direct interaction with
> on-disk format when:
>   - flipping SFrame contents before decoding them in sframe_decode.
>   - flipping SFrame contents before writing them out in sframe_encode.
> 
> ---
> [No changes in V2]
> ---

One nit below.

Reviewed-by: Jens Remus <jremus@linux.ibm.com>

> diff --git a/libsframe/sframe.c b/libsframe/sframe.c

> @@ -26,13 +26,22 @@
>  #include "sframe-impl.h"
>  #include "swap.h"
>  
> -typedef sframe_func_desc_entry_v2 sframe_func_desc_entry;
> +/* Representation of SFrame FDE internal to libsframe.  */
> +typedef struct sframe_func_desc_entry_int
> +{
> +  int64_t func_start_addr;
> +  uint32_t func_size;
> +  uint32_t func_start_fre_off;
> +  uint32_t func_num_fres;
> +  uint8_t func_info;
> +  uint8_t func_rep_size;
> +} ATTRIBUTE_PACKED sframe_func_desc_entry_int;

Why use ATTRIBUTE_PACKED on the internal representation?  It might cause
less performant access to the members.  Omit that as it is also done for
struct sframe_frame_row_entry.

Regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303)
+49-7031-16-1128 Office
jremus@de.ibm.com

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