[review v2] gdb: recognize new DWARF attributes: defaulted, deleted, calling conv.

["Simon Marchi (Code Review)" <gerrit@gnutoolchain-gerrit.osci.io>]

Simon Marchi has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/135
......................................................................


Patch Set 2:

(3 comments)

Thanks for the update.  Just two minor comments about the validation.

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/135/2/gdb/dwarf2read.c 
File gdb/dwarf2read.c:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/135/2/gdb/dwarf2read.c@15831 
PS2, Line 15831: 
15822 | is_valid_DW_AT_calling_convention (ULONGEST value)
      | ...
15826 |     case DW_CC_normal:
15827 |     case DW_CC_program:
15828 |     case DW_CC_nocall:
15829 |     case DW_CC_pass_by_reference:
15830 |     case DW_CC_pass_by_value:
15831 >     case DW_CC_lo_user:
15832 >     case DW_CC_hi_user:
15833 |     /* case DW_CC_GNU_renesas_sh: Duplicate of DW_CC_lo_user.  */
15834 |     case DW_CC_GNU_borland_fastcall_i386:
15835 |     /* case DW_CC_GDB_IBM_OpenCL: Duplicate of DW_CC_hi_user.  */
15836 |       return true;
15837 |     }

I don' think we should include lo_user and hi_user in the switch, since they are not "real" values.  They just indicate the range for vendor-specific values.

DW_CC_GNU_renesas_sh and DW_CC_GDB_IBM_OpenCL are "real" values, so they should be included in the switch.  In the end, the behavior will be the same, since as you noted, they are duplicates of lo_user and hi_user.


https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/135/2/gdb/dwarf2read.c@15928 
PS2, Line 15928: 
15857 | read_structure_type (struct die_info *die, struct dwarf2_cu *cu)
      | ...
15923 |     TYPE_DECLARED_CLASS (type) = 1;
15924 | 
15925 |   /* Store the calling convention in the type if it's available in
15926 |      the die.  Otherwise the calling convention remains set to
15927 |      the default value DW_CC_normal.  */
15928 >   attr = dwarf2_attr (die, DW_AT_calling_convention, cu);
15929 |   if (attr != nullptr
15930 |       && is_valid_DW_AT_calling_convention (DW_UNSND (attr)))
15931 |     {
15932 |       ALLOCATE_CPLUS_STRUCT_TYPE (type);
15933 |       TYPE_CPLUS_CALLING_CONVENTION (type)

According to table 5.5 of DWARF5, the acceptable calling convention values for types are restricted to:

- DW_CC_normal
- DW_CC_pass_by_value
- DW_CC_pass_by_reference

So should we complain and reject the value if it's not one of those? The idea is that if a producer emits an unacceptable value by mistake, the issue is caught as early as possible rather than silently accepted.

In the spot where we read DW_AT_calling_convention for subroutines, we could validate that the value is one of those listed in table 3.3:

- DW_CC_normal
- DW_CC_program
- DW_CC_nocall

... plus the vendor-specific values that we support.  So it might be simpler to do two functions, is_valid_DW_AT_calling_convention_for_types and is_valid_DW_AT_calling_convention_for_subprogram. Therefore, in this patch I suggest calling the new function "is_valid_DW_AT_calling_convention_for_types" to leave room to do the same thing for subprograms.


https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/135/1/gdb/gdbtypes.h 
File gdb/gdbtypes.h:

https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/135/1/gdb/gdbtypes.h@1144 
PS1, Line 1144: 
1137 | struct func_type
     | ...
1139 |     /* * The calling convention for targets supporting multiple ABIs.
1140 |        Right now this is only fetched from the Dwarf-2
1141 |        DW_AT_calling_convention attribute.  The value is one of the
1142 |        DW_CC enum dwarf_calling_convention constants.  */
1143 | 
1144 >     unsigned calling_convention : 8;
1145 | 
1146 |     /* * Whether this function normally returns to its caller.  It is
1147 |        set from the DW_AT_noreturn attribute if set on the
1148 |        DW_TAG_subprogram.  */
1149 | 

> This is an existing definition I had aimed to be consistent with.

Ack, let's change it in another patch.



-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I54192f363115b78ec7435a8563b73fcace420765
Gerrit-Change-Number: 135
Gerrit-PatchSet: 2
Gerrit-Owner: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Gerrit-Reviewer: Andrew Burgess <andrew.burgess@embecosm.com>
Gerrit-Reviewer: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Gerrit-CC: Simon Marchi <simon.marchi@polymtl.ca>
Gerrit-CC: Tom Tromey <tromey@sourceware.org>
Gerrit-Comment-Date: Thu, 31 Oct 2019 17:57:30 +0000
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Comment-In-Reply-To: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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