[RFA] Use gdb::byte_vector when reading section data

  This changes a couple of spots that read section data to use
gdb::byte_vector rather than a cleanup.

Regression tested by the buildbot.  I am not certain that the buildbot
actually tests the code in question, so I recommend careful review.

gdb/ChangeLog
2018-03-09  Tom Tromey  <tom@tromey.com>

	* rs6000-aix-tdep.c (rs6000_aix_core_xfer_shared_libraries_aix):
	Use gdb::byte_vector.
	* arm-tdep.c (arm_exidx_new_objfile): Use gdb::byte_vector.
---
 gdb/ChangeLog         |  6 ++++++
 gdb/arm-tdep.c        | 39 +++++++++++++++------------------------
 gdb/rs6000-aix-tdep.c | 15 ++++-----------
 3 files changed, 25 insertions(+), 35 deletions(-)
  

> This changes a couple of spots that read section data to use
> gdb::byte_vector rather than a cleanup.
> 
> Regression tested by the buildbot.  I am not certain that the buildbot
> actually tests the code in question, so I recommend careful review.
> 
> gdb/ChangeLog
> 2018-03-09  Tom Tromey  <tom@tromey.com>
> 
> 	* rs6000-aix-tdep.c (rs6000_aix_core_xfer_shared_libraries_aix):
> 	Use gdb::byte_vector.
> 	* arm-tdep.c (arm_exidx_new_objfile): Use gdb::byte_vector.

FWIW, I gave this patch a careful read, and it looked sane to me.
But I only consider myself a yellow-belt-C++-student, so a careful
review from someone else would be useful too.

As far as I can tell, the buildbots include ppc-aix, so the patch
was tested there as well, so additional runs would probably not
help, right? (I am pretty sure that the shared library code is
exercised).


> ---
>  gdb/ChangeLog         |  6 ++++++
>  gdb/arm-tdep.c        | 39 +++++++++++++++------------------------
>  gdb/rs6000-aix-tdep.c | 15 ++++-----------
>  3 files changed, 25 insertions(+), 35 deletions(-)
> 
> diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
> index ef7e66b36a..52d3f41cee 100644
> --- a/gdb/arm-tdep.c
> +++ b/gdb/arm-tdep.c
> @@ -2040,50 +2040,41 @@ arm_obj_section_from_vma (struct objfile *objfile, bfd_vma vma)
>  static void
>  arm_exidx_new_objfile (struct objfile *objfile)
>  {
> -  struct cleanup *cleanups;
>    struct arm_exidx_data *data;
>    asection *exidx, *extab;
>    bfd_vma exidx_vma = 0, extab_vma = 0;
>    bfd_size_type exidx_size = 0, extab_size = 0;
> -  gdb_byte *exidx_data = NULL, *extab_data = NULL;
>    LONGEST i;
>  
>    /* If we've already touched this file, do nothing.  */
>    if (!objfile || objfile_data (objfile, arm_exidx_data_key) != NULL)
>      return;
> -  cleanups = make_cleanup (null_cleanup, NULL);
>  
>    /* Read contents of exception table and index.  */
>    exidx = bfd_get_section_by_name (objfile->obfd, ELF_STRING_ARM_unwind);
> +  gdb::byte_vector exidx_data;
>    if (exidx)
>      {
>        exidx_vma = bfd_section_vma (objfile->obfd, exidx);
>        exidx_size = bfd_get_section_size (exidx);
> -      exidx_data = (gdb_byte *) xmalloc (exidx_size);
> -      make_cleanup (xfree, exidx_data);
> +      exidx_data.resize (exidx_size);
>  
>        if (!bfd_get_section_contents (objfile->obfd, exidx,
> -				     exidx_data, 0, exidx_size))
> -	{
> -	  do_cleanups (cleanups);
> -	  return;
> -	}
> +				     exidx_data.data (), 0, exidx_size))
> +	return;
>      }
>  
>    extab = bfd_get_section_by_name (objfile->obfd, ".ARM.extab");
> +  gdb::byte_vector extab_data;
>    if (extab)
>      {
>        extab_vma = bfd_section_vma (objfile->obfd, extab);
>        extab_size = bfd_get_section_size (extab);
> -      extab_data = (gdb_byte *) xmalloc (extab_size);
> -      make_cleanup (xfree, extab_data);
> +      extab_data.resize (extab_size);
>  
>        if (!bfd_get_section_contents (objfile->obfd, extab,
> -				     extab_data, 0, extab_size))
> -	{
> -	  do_cleanups (cleanups);
> -	  return;
> -	}
> +				     extab_data.data (), 0, extab_size))
> +	return;
>      }
>  
>    /* Allocate exception table data structure.  */
> @@ -2097,8 +2088,9 @@ arm_exidx_new_objfile (struct objfile *objfile)
>    for (i = 0; i < exidx_size / 8; i++)
>      {
>        struct arm_exidx_entry new_exidx_entry;
> -      bfd_vma idx = bfd_h_get_32 (objfile->obfd, exidx_data + i * 8);
> -      bfd_vma val = bfd_h_get_32 (objfile->obfd, exidx_data + i * 8 + 4);
> +      bfd_vma idx = bfd_h_get_32 (objfile->obfd, exidx_data.data () + i * 8);
> +      bfd_vma val = bfd_h_get_32 (objfile->obfd,
> +				  exidx_data.data () + i * 8 + 4);
>        bfd_vma addr = 0, word = 0;
>        int n_bytes = 0, n_words = 0;
>        struct obj_section *sec;
> @@ -2135,7 +2127,7 @@ arm_exidx_new_objfile (struct objfile *objfile)
>  	  if (addr >= extab_vma && addr + 4 <= extab_vma + extab_size)
>  	    {
>  	      word = bfd_h_get_32 (objfile->obfd,
> -				   extab_data + addr - extab_vma);
> +				   extab_data.data () + addr - extab_vma);
>  	      addr += 4;
>  
>  	      if ((word & 0xff000000) == 0x80000000)
> @@ -2193,7 +2185,8 @@ arm_exidx_new_objfile (struct objfile *objfile)
>  		      && addr + 4 <= extab_vma + extab_size)
>  		    {
>  		      word = bfd_h_get_32 (objfile->obfd,
> -					   extab_data + addr - extab_vma);
> +					   (extab_data.data ()
> +					    + addr - extab_vma));
>  		      addr += 4;
>  		      n_bytes = 3;
>  		      n_words = ((word >> 24) & 0xff);
> @@ -2222,7 +2215,7 @@ arm_exidx_new_objfile (struct objfile *objfile)
>  	  while (n_words--)
>  	    {
>  	      word = bfd_h_get_32 (objfile->obfd,
> -				   extab_data + addr - extab_vma);
> +				   extab_data.data () + addr - extab_vma);
>  	      addr += 4;
>  
>  	      *p++ = (gdb_byte) ((word >> 24) & 0xff);
> @@ -2243,8 +2236,6 @@ arm_exidx_new_objfile (struct objfile *objfile)
>  		     data->section_maps[sec->the_bfd_section->index],
>  		     &new_exidx_entry);
>      }
> -
> -  do_cleanups (cleanups);
>  }
>  
>  /* Search for the exception table entry covering MEMADDR.  If one is found,
> diff --git a/gdb/rs6000-aix-tdep.c b/gdb/rs6000-aix-tdep.c
> index 38c86d4cd8..e3e086c210 100644
> --- a/gdb/rs6000-aix-tdep.c
> +++ b/gdb/rs6000-aix-tdep.c
> @@ -1007,9 +1007,6 @@ rs6000_aix_core_xfer_shared_libraries_aix (struct gdbarch *gdbarch,
>  {
>    struct bfd_section *ldinfo_sec;
>    int ldinfo_size;
> -  gdb_byte *ldinfo_buf;
> -  struct cleanup *cleanup;
> -  LONGEST result;
>  
>    ldinfo_sec = bfd_get_section_by_name (core_bfd, ".ldinfo");
>    if (ldinfo_sec == NULL)
> @@ -1017,19 +1014,15 @@ rs6000_aix_core_xfer_shared_libraries_aix (struct gdbarch *gdbarch,
>  	   bfd_errmsg (bfd_get_error ()));
>    ldinfo_size = bfd_get_section_size (ldinfo_sec);
>  
> -  ldinfo_buf = (gdb_byte *) xmalloc (ldinfo_size);
> -  cleanup = make_cleanup (xfree, ldinfo_buf);
> +  gdb::byte_vector ldinfo_buf (ldinfo_size);
>  
>    if (! bfd_get_section_contents (core_bfd, ldinfo_sec,
> -				  ldinfo_buf, 0, ldinfo_size))
> +				  ldinfo_buf.data (), 0, ldinfo_size))
>      error (_("unable to read .ldinfo section from core file: %s"),
>  	  bfd_errmsg (bfd_get_error ()));
>  
> -  result = rs6000_aix_ld_info_to_xml (gdbarch, ldinfo_buf, readbuf,
> -				      offset, len, 0);
> -
> -  do_cleanups (cleanup);
> -  return result;
> +  return rs6000_aix_ld_info_to_xml (gdbarch, ldinfo_buf.data (), readbuf,
> +				    offset, len, 0);
>  }
>  
>  static void
> -- 
> 2.13.6
  

On 2018-03-11 10:11 AM, Joel Brobecker wrote:
>> This changes a couple of spots that read section data to use
>> gdb::byte_vector rather than a cleanup.
>>
>> Regression tested by the buildbot.  I am not certain that the buildbot
>> actually tests the code in question, so I recommend careful review.
>>
>> gdb/ChangeLog
>> 2018-03-09  Tom Tromey  <tom@tromey.com>
>>
>> 	* rs6000-aix-tdep.c (rs6000_aix_core_xfer_shared_libraries_aix):
>> 	Use gdb::byte_vector.
>> 	* arm-tdep.c (arm_exidx_new_objfile): Use gdb::byte_vector.
> 
> FWIW, I gave this patch a careful read, and it looked sane to me.
> But I only consider myself a yellow-belt-C++-student, so a careful
> review from someone else would be useful too.
> 
> As far as I can tell, the buildbots include ppc-aix, so the patch
> was tested there as well, so additional runs would probably not
> help, right? (I am pretty sure that the shared library code is
> exercised).

LGTM too, though in arm-tdep.c, I would suggest getting rid of the
exidx_size and extab_size variables, and to use the std::vector::size
instead.

Simon