[ Adding Jason as addressee ]
On 08/28/2018 08:20 PM, Omar Sandoval wrote:
> On Fri, Aug 17, 2018 at 12:16:07AM -0700, Omar Sandoval wrote:
>> On Thu, Aug 16, 2018 at 11:54:53PM -0700, Omar Sandoval wrote:
>>> On Thu, Aug 16, 2018 at 10:27:48PM -0700, Andrew Pinski wrote:
>>>> On Thu, Aug 16, 2018 at 9:29 PM Omar Sandoval <[email protected]> wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> This fixes the issue that it is impossible to distinguish a zero-length
>>>>> array
>>>>> type from a flexible array type given the DWARF produced by GCC (which I
>>>>> reported here [1]). We do so by adding a DW_AT_count attribute with a
>>>>> value of
>>>>> zero only for zero-length arrays (this is what clang does in this case,
>>>>> too).
>>>>>
>>>>> 1: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86985
>>>>>
>>>>> The reproducer from the PR now produces the expected output:
>>>>>
>>>>> $ ~/gcc-build/gcc/xgcc -B ~/gcc-build/gcc -g -c zero_length.c
>>>>> $ ~/gcc-build/gcc/xgcc -B ~/gcc-build/gcc -g -c flexible.c
>>>>> $ gdb -batch -ex 'ptype baz' zero_length.o
>>>>> type = struct {
>>>>> int foo;
>>>>> int bar[0];
>>>>> }
>>>>> $ gdb -batch -ex 'ptype baz' flexible.o
>>>>> type = struct {
>>>>> int foo;
>>>>> int bar[];
>>>>> }
>>>>>
>>>>> This was bootstrapped and tested on x86_64-pc-linux-gnu.
>>>>>
>>>>> I don't have commit rights (first time contributor), so if this change is
>>>>> okay
>>>>> could it please be applied?
>>
>> [snip]
>>
>> Here's the patch with the is_c () helper instead.
>>
>> 2018-08-17 Omar Sandoval <[email protected]>
>>
I've added the PR number here.
>> * dwarf2out.c (is_c): New.
>> (add_subscript_info): Add DW_AT_count of 0 for C zero-length arrays.
>>
>> diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
>> index 5a74131d332..189f9bb381f 100644
>> --- a/gcc/dwarf2out.c
>> +++ b/gcc/dwarf2out.c
>> @@ -3671,6 +3671,7 @@ static const char *get_AT_string (dw_die_ref, enum
>> dwarf_attribute);
>> static int get_AT_flag (dw_die_ref, enum dwarf_attribute);
>> static unsigned get_AT_unsigned (dw_die_ref, enum dwarf_attribute);
>> static inline dw_die_ref get_AT_ref (dw_die_ref, enum dwarf_attribute);
>> +static bool is_c (void);
>> static bool is_cxx (void);
>> static bool is_cxx (const_tree);
>> static bool is_fortran (void);
>> @@ -5434,6 +5435,19 @@ get_AT_file (dw_die_ref die, enum dwarf_attribute
>> attr_kind)
>> return a ? AT_file (a) : NULL;
>> }
>>
>> +/* Return TRUE if the language is C. */
>> +
>> +static inline bool
>> +is_c (void)
>> +{
>> + unsigned int lang = get_AT_unsigned (comp_unit_die (), DW_AT_language);
>> +
>> + return (lang == DW_LANG_C || lang == DW_LANG_C89 || lang == DW_LANG_C99
>> + || lang == DW_LANG_C11 || lang == DW_LANG_ObjC);
>> +
>> +
>> +}
>> +
>> /* Return TRUE if the language is C++. */
>>
>> static inline bool
>> @@ -20918,12 +20932,24 @@ add_subscript_info (dw_die_ref type_die, tree
>> type, bool collapse_p)
>> dimension arr(N:*)
>> Since the debugger is definitely going to need to know N
>> to produce useful results, go ahead and output the lower
>> - bound solo, and hope the debugger can cope. */
>> + bound solo, and hope the debugger can cope.
>> +
>> + For C and C++, if upper is NULL, this may be a zero-length array
>> + or a flexible array; we'd like to be able to distinguish between
>> + the two. Set DW_AT_count to 0 for the former. TYPE_SIZE is NULL
>> + for the latter. */
>>
I found inserting this comment here confusing, I've moved it down and
shortened it.
>> if (!get_AT (subrange_die, DW_AT_lower_bound))
>> add_bound_info (subrange_die, DW_AT_lower_bound, lower, NULL);
>> - if (upper && !get_AT (subrange_die, DW_AT_upper_bound))
>> - add_bound_info (subrange_die, DW_AT_upper_bound, upper, NULL);
>> + if (!get_AT (subrange_die, DW_AT_upper_bound)
>> + && !get_AT (subrange_die, DW_AT_count))
>> + {
>> + if (upper)
>> + add_bound_info (subrange_die, DW_AT_upper_bound, upper, NULL);
>> + else if ((is_c () || is_cxx ()) && TYPE_SIZE (type))
>> + add_bound_info (subrange_die, DW_AT_count,
>> + build_int_cst (TREE_TYPE (lower), 0), NULL);
>> + }
>> }
>>
>> /* Otherwise we have an array type with an unspecified length. The
>
> Ping. Does this version look okay for trunk?
>
Looks ok to me (but I can't approve).
Also, I've added a testcase.
OK for trunk?
Thanks,
- Tom
[debug] DWARF: add DW_AT_count to zero-length arrays
2018-09-04 Omar Sandoval <[email protected]>
Tom de Vries <[email protected]>
PR debug/86985
* dwarf2out.c (is_c): New function.
(add_subscript_info): Add DW_AT_count of 0 for C zero-length arrays.
* gcc.dg/guality/zero-length-array.c: New test.
---
gcc/dwarf2out.c | 26 ++++++++++++++++++++++--
gcc/testsuite/gcc.dg/guality/zero-length-array.c | 21 +++++++++++++++++++
2 files changed, 45 insertions(+), 2 deletions(-)
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 77317ed2575..58c3906cdbf 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -3679,6 +3679,7 @@ static const char *get_AT_string (dw_die_ref, enum dwarf_attribute);
static int get_AT_flag (dw_die_ref, enum dwarf_attribute);
static unsigned get_AT_unsigned (dw_die_ref, enum dwarf_attribute);
static inline dw_die_ref get_AT_ref (dw_die_ref, enum dwarf_attribute);
+static bool is_c (void);
static bool is_cxx (void);
static bool is_cxx (const_tree);
static bool is_fortran (void);
@@ -5442,6 +5443,19 @@ get_AT_file (dw_die_ref die, enum dwarf_attribute attr_kind)
return a ? AT_file (a) : NULL;
}
+/* Return TRUE if the language is C. */
+
+static inline bool
+is_c (void)
+{
+ unsigned int lang = get_AT_unsigned (comp_unit_die (), DW_AT_language);
+
+ return (lang == DW_LANG_C || lang == DW_LANG_C89 || lang == DW_LANG_C99
+ || lang == DW_LANG_C11 || lang == DW_LANG_ObjC);
+
+
+}
+
/* Return TRUE if the language is C++. */
static inline bool
@@ -20952,8 +20966,16 @@ add_subscript_info (dw_die_ref type_die, tree type, bool collapse_p)
if (!get_AT (subrange_die, DW_AT_lower_bound))
add_bound_info (subrange_die, DW_AT_lower_bound, lower, NULL);
- if (upper && !get_AT (subrange_die, DW_AT_upper_bound))
- add_bound_info (subrange_die, DW_AT_upper_bound, upper, NULL);
+ if (!get_AT (subrange_die, DW_AT_upper_bound)
+ && !get_AT (subrange_die, DW_AT_count))
+ {
+ if (upper)
+ add_bound_info (subrange_die, DW_AT_upper_bound, upper, NULL);
+ else if ((is_c () || is_cxx ()) && TYPE_SIZE (type))
+ /* Zero-length array. */
+ add_bound_info (subrange_die, DW_AT_count,
+ build_int_cst (TREE_TYPE (lower), 0), NULL);
+ }
}
/* Otherwise we have an array type with an unspecified length. The
diff --git a/gcc/testsuite/gcc.dg/guality/zero-length-array.c b/gcc/testsuite/gcc.dg/guality/zero-length-array.c
new file mode 100644
index 00000000000..33f34d98ac2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/guality/zero-length-array.c
@@ -0,0 +1,21 @@
+/* PR debug/86985 */
+/* { dg-do run } */
+/* { dg-options "-g" } */
+
+struct {
+ int foo;
+ int bar[0];
+} zla; /* Zero length array. */
+
+struct {
+ int foo;
+ int bar[];
+} fam; /* Flexible array member. */
+
+int
+main ()
+{
+ /* { dg-final { gdb-test . "type:zla" "struct { int foo; int bar[0]; }" } } */
+ /* { dg-final { gdb-test . "type:fam" "struct { int foo; int bar[]; }" } } */
+ return 0;
+}
