[PATCH v4 2/2] Implement pahole-like 'ptype /o' option

[Simon Marchi]

On 2017-12-11 06:43 PM, Sergio Durigan Junior wrote:
> This commit implements the pahole-like '/o' option for 'ptype', which
> prints the offsets and sizes of struct fields, reporting whenever
> there is a hole found.
> 
> The output is heavily based on pahole(1), with a few modifications
> here and there to adjust it to our reality.  Here's an example:
> 
>   (gdb) ptype /o stap_probe
>   /* offset    |  size */
>   struct stap_probe {
>   /*    0      |    40 */    struct probe {
>   /*    0      |     8 */        const probe_ops *pops;
>   /*    8      |     8 */        gdbarch *arch;
>   /*   16      |     8 */        const char *name;
>   /*   24      |     8 */        const char *provider;
>   /*   32      |     8 */        CORE_ADDR address;
> 			     } /* total size:   40 bytes */ p;
>   /*   40      |     8 */    CORE_ADDR sem_addr;
>   /*   48:31   |     4 */    unsigned int args_parsed : 1;
>   /* XXX  7-bit hole   */
>   /* XXX  7-byte hole  */
>   /*   56      |     8 */    union {
>   /*                 8 */        const char *text;
>   /*                 8 */        VEC_stap_probe_arg_s *vec;
> 			     } /* total size:    8 bytes */ args_u;
>   } /* total size:   64 bytes */
> 
> A big part of this patch handles the formatting logic of 'ptype',
> which is a bit messy.  I tried to be not very invasive, but I had to
> do some cleanups here and there to make life easier.
> 
> This patch is the start of a long-term work I'll do to flush the local
> patches we carry for Fedora GDB.  In this specific case, I'm aiming at
> upstreaming the feature implemented by the 'pahole.py' script that is
> shipped with Fedora GDB:
> 
>   <https://src.fedoraproject.org/rpms/gdb/blob/master/f/gdb-archer.patch#_311>
> 
> This has been regression-tested on the BuildBot.  There's a new
> testcase for it, along with an update to the documentation.  I also
> thought it was worth mentioning this feature in the NEWS file.

That patch LGTM as-is, as well as with the union offsets :)

Simon