On 8/25/25 10:33, Indu Bhagat wrote:
> On 8/25/25 8:08 AM, David Faust wrote:
>>
>>
>> On 8/22/25 23:49, Indu Bhagat wrote:
>>> On 8/6/25 9:26 AM, David Faust wrote:
>>>> CTF array encoding uses uint32 for number of elements. This means there
>>>> is a hard upper limit on array types which the format can represent.
>>>>
>>>
>>> Hi David,
>>>
>>> Thanks for the patch.
>>>
>>> Few nits. But otherwise the patch looks good. As you noted in the
>>> bugzilla, more fixes will be needed to fix the ctf_die_bitsize () return
>>> type and its consumers...
>>
>> Just to clarify, OK to push with the nits below addressed?
>>
>> (I'll follow up with the other fixes mentioned in the PR soon, just
>> been a little sidetracked recently)
>>
>
> Yes, IMO its good to be committed.
And pushed, with the nits fixed.
Thanks
>
>>>
>>>> GCC internally was also using a uint32_t for this, which would overflow
>>>> when translating from DWARF for arrays with more with more than
>>>
>>> typo: "with more with more"
>>
>> Oops. Thanks.
>>
>>>
>>>> UINT32_MAX elements. Use an unsigned HOST_WIDE_INT instead to fetch
>>>> the array bound, and fall back to CTF_K_UNKNOWN if the array cannot
>>>> be represented in CTF.
>>>>
>>>> Tested on x86_64-pc-linux-gnu.
>>>>
>>>> PR debug/121411
>>>>
>>>> gcc/
>>>>
>>>> * dwarf2ctf.cc (gen_ctf_subrange_type): Use unsigned HWI for
>>>> array_num_elements. Fallback to CTF_K_UNKNOWN if the array
>>>> type has too many elements for CTF to represent.
>>>>
>>>> gcc/testsuite/
>>>>
>>>> * gcc.dg/debug/ctf/ctf-array-7.c: New test.
>>>> ---
>>>> gcc/dwarf2ctf.cc | 12 +++++++---
>>>> gcc/testsuite/gcc.dg/debug/ctf/ctf-array-7.c | 23 ++++++++++++++++++++
>>>> 2 files changed, 32 insertions(+), 3 deletions(-)
>>>> create mode 100644 gcc/testsuite/gcc.dg/debug/ctf/ctf-array-7.c
>>>>
>>>> diff --git a/gcc/dwarf2ctf.cc b/gcc/dwarf2ctf.cc
>>>> index 7de3696a4d7..b0ad18a556c 100644
>>>> --- a/gcc/dwarf2ctf.cc
>>>> +++ b/gcc/dwarf2ctf.cc
>>>> @@ -361,7 +361,7 @@ gen_ctf_subrange_type (ctf_container_ref ctfc,
>>>> ctf_dtdef_ref array_elems_type,
>>>>
>>>> dw_attr_node *upper_bound_at;
>>>> dw_die_ref array_index_type;
>>>> - uint32_t array_num_elements;
>>>> + unsigned HOST_WIDE_INT array_num_elements;
>>>>
>>>> if (dw_get_die_tag (c) == DW_TAG_subrange_type)
>>>> {
>>>> @@ -376,9 +376,9 @@ gen_ctf_subrange_type (ctf_container_ref ctfc,
>>>> ctf_dtdef_ref array_elems_type,
>>>> if (upper_bound_at
>>>> && AT_class (upper_bound_at) == dw_val_class_unsigned_const)
>>>> /* This is the upper bound index. */
>>>> - array_num_elements = get_AT_unsigned (c, DW_AT_upper_bound) + 1;
>>>> + array_num_elements = AT_unsigned (get_AT (c, DW_AT_upper_bound)) + 1;
>>>> else if (get_AT (c, DW_AT_count))
>>>> - array_num_elements = get_AT_unsigned (c, DW_AT_count);
>>>> + array_num_elements = AT_unsigned (get_AT (c, DW_AT_count));
>>>> else
>>>> {
>>>> /* This is a VLA of some kind. */
>>>> @@ -388,6 +388,12 @@ gen_ctf_subrange_type (ctf_container_ref ctfc,
>>>> ctf_dtdef_ref array_elems_type,
>>>> else
>>>> gcc_unreachable ();
>>>>
>>>> + if (array_num_elements > UINT32_MAX)
>>>> + {
>>>> + /* The array cannot be encoded in CTF. */
>>>> + return gen_ctf_unknown_type (ctfc);
>>>> + }
>>>> +
>>>
>>> Is it possible to annotate this with "TBD_CTF_REPRESENTATION_LIMIT" in
>>> the comment ?
>>
>> Sure, as a marker for the future right? Will add it.
>>
>> /* The array cannot be encoded in CTF. TBD_CTF_REPRESENTATION_LIMIT. */
>>
>>
>
> Yes, just a marker. Thanks.
>
>>>
>>>> /* Ok, mount and register the array type. Note how the array
>>>> type we register here is the type of the elements in
>>>> subsequent "dimensions", if there are any. */
>>>> diff --git a/gcc/testsuite/gcc.dg/debug/ctf/ctf-array-7.c
>>>> b/gcc/testsuite/gcc.dg/debug/ctf/ctf-array-7.c
>>>> new file mode 100644
>>>> index 00000000000..01accc7c18f
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/debug/ctf/ctf-array-7.c
>>>> @@ -0,0 +1,23 @@
>>>> +/* CTF generation for array which cannot be encoded in CTF.
>>>> +
>>>> + CTF encoding uses a uint32 for number of elements in an array which
>>>> + means there is a hard upper limit on sizes of arrays which can be
>>>> + represented. Arrays with too many elements are encoded with
>>>> + CTF_K_UNKNOWN to indicate that they cannot be represented. */
>>>> +
>>>> +/* { dg-do compile } */
>>>> +/* { dg-options "-O0 -gctf -dA" } */
>>>> +
>>>> +int rep[0xffffffff];
>>>> +int unrep[0x100000000];
>>>> +
>>>> +/* One dimension can be represented, other cannot.
>>>> + Result is a (representable) array with unknown element type. */
>>>> +int unrepdim [0xab][0x100000007];
>>>> +
>>>> +/* Two CTF_K_ARRAY, one (shared) CTF_K_UNKNOWN. */
>>>> +/* { dg-final { scan-assembler-times "0x12000000\[\t \]+\[^\n\]*ctt_info"
>>>> 2 } } */
>>>> +/* { dg-final { scan-assembler-times "0x2000000\[\t \]+\[^\n\]*ctt_info"
>>>> 1 } } */
>>>> +
>>>> +/* { dg-final { scan-assembler-times "\[\t \]+0xffffffff\[\t
>>>> \]+\[^\n\]*cta_nelems" 1 } } */
>>>> +/* { dg-final { scan-assembler-times "\[\t \]+0xab\[\t
>>>> \]+\[^\n\]*cta_nelems" 1 } } */
>>>
>>
>
