* GDB returns wrong type when traversing optimized-out Fields
@ 2018-02-05 4:02 Roman Popov
2018-02-05 4:07 ` Roman Popov
0 siblings, 1 reply; 4+ messages in thread
From: Roman Popov @ 2018-02-05 4:02 UTC (permalink / raw)
To: gdb
Hi all,
I've encountered strange GDB behavior when requesting a value of
optimized-away field.
Instead of returning None or raising exception, GDB returns an
optimizied-out value of wrong type.
Here is a small reproducer *optimize_out.cpp*:
template <unsigned v1, unsigned v2>
struct TRAITS {
static const unsigned val1 = v1;
static const unsigned val2 = v2;
};
template < class TRAITS >
struct foo {
static const unsigned x1 = TRAITS::v1;
static const unsigned x2 = TRAITS::v2;
};
int main () {
foo<TRAITS<1,2>> f1;
// SET BREAKPOINT HERE
return 0;
}
# Using g++ 7.3
$ g++ -g optimize_out.cpp
# Using gdb 8.1
$ gdb a.out
(gdb) break optimize_out.cpp:14
(gdb) r
(gdb) p f1
$1 = {static x1 = <optimized out>, static x2 = <optimized out>}
Ok, looks good. Now traverse fields:
(gdb) python
>f1 = gdb.parse_and_eval("f1")
>for field in f1.type.fields():
> print ("field name: ", field.name, "field type: ", field.type)
> field_val = f1[field]
> print ("optout?: ",field_val.is_optimized_out, "type: ",field_val.type)
>end
field name: x1 field type: const unsigned int
optout?: True type: foo<TRAITS<1, 2> >
field name: x2 field type: const unsigned int
optout?: True type: foo<TRAITS<1, 2> >
So type we get is foo<TRAITS<1, 2> >, not unsigned int.
Looks like GDB-MI has same behavior. At least this code sample totatlly
confuses GDB GUI I use.
Thanks,
Roman
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: GDB returns wrong type when traversing optimized-out Fields
2018-02-05 4:02 GDB returns wrong type when traversing optimized-out Fields Roman Popov
@ 2018-02-05 4:07 ` Roman Popov
2018-02-05 5:39 ` Simon Marchi
0 siblings, 1 reply; 4+ messages in thread
From: Roman Popov @ 2018-02-05 4:07 UTC (permalink / raw)
To: gdb
I apologize for code typo in previous email. Here is correct code sample:
template <unsigned v1, unsigned v2>
struct TRAITS {
static const unsigned val1 = v1;
static const unsigned val2 = v2;
};
template < class TRAITS >
struct foo {
static const unsigned x1 = TRAITS::val1;
static const unsigned x2 = TRAITS::val2;
};
int main () {
foo<TRAITS<1,2>> f1;
// SET BREAKPOINT HERE
return 0;
}
-Roman
2018-02-04 20:02 GMT-08:00 Roman Popov <ripopov@gmail.com>:
> Hi all,
> I've encountered strange GDB behavior when requesting a value of
> optimized-away field.
> Instead of returning None or raising exception, GDB returns an
> optimizied-out value of wrong type.
>
> Here is a small reproducer *optimize_out.cpp*:
>
> template <unsigned v1, unsigned v2>
> struct TRAITS {
> static const unsigned val1 = v1;
> static const unsigned val2 = v2;
> };
> template < class TRAITS >
> struct foo {
> static const unsigned x1 = TRAITS::v1;
> static const unsigned x2 = TRAITS::v2;
> };
>
> int main () {
> foo<TRAITS<1,2>> f1;
> // SET BREAKPOINT HERE
> return 0;
> }
>
> # Using g++ 7.3
> $ g++ -g optimize_out.cpp
>
> # Using gdb 8.1
> $ gdb a.out
>
> (gdb) break optimize_out.cpp:14
> (gdb) r
> (gdb) p f1
> $1 = {static x1 = <optimized out>, static x2 = <optimized out>}
>
> Ok, looks good. Now traverse fields:
>
> (gdb) python
> >f1 = gdb.parse_and_eval("f1")
> >for field in f1.type.fields():
> > print ("field name: ", field.name, "field type: ", field.type)
> > field_val = f1[field]
> > print ("optout?: ",field_val.is_optimized_out, "type:
> ",field_val.type)
> >end
> field name: x1 field type: const unsigned int
> optout?: True type: foo<TRAITS<1, 2> >
> field name: x2 field type: const unsigned int
> optout?: True type: foo<TRAITS<1, 2> >
>
>
>
> So type we get is foo<TRAITS<1, 2> >, not unsigned int.
>
> Looks like GDB-MI has same behavior. At least this code sample totatlly
> confuses GDB GUI I use.
>
> Thanks,
> Roman
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: GDB returns wrong type when traversing optimized-out Fields
2018-02-05 4:07 ` Roman Popov
@ 2018-02-05 5:39 ` Simon Marchi
2018-02-05 6:20 ` Roman Popov
0 siblings, 1 reply; 4+ messages in thread
From: Simon Marchi @ 2018-02-05 5:39 UTC (permalink / raw)
To: Roman Popov, gdb
On 2018-02-04 11:06 PM, Roman Popov wrote:
> I apologize for code typo in previous email. Here is correct code sample:
>
> template <unsigned v1, unsigned v2>
> struct TRAITS {
> static const unsigned val1 = v1;
> static const unsigned val2 = v2;
> };
> template < class TRAITS >
> struct foo {
> static const unsigned x1 = TRAITS::val1;
> static const unsigned x2 = TRAITS::val2;
> };
>
> int main () {
> foo<TRAITS<1,2>> f1;
> // SET BREAKPOINT HERE
> return 0;
> }
>
> -Roman
>
>
> 2018-02-04 20:02 GMT-08:00 Roman Popov <ripopov@gmail.com>:
>
>> Hi all,
>> I've encountered strange GDB behavior when requesting a value of
>> optimized-away field.
>> Instead of returning None or raising exception, GDB returns an
>> optimizied-out value of wrong type.
>>
>> Here is a small reproducer *optimize_out.cpp*:
>>
>> template <unsigned v1, unsigned v2>
>> struct TRAITS {
>> static const unsigned val1 = v1;
>> static const unsigned val2 = v2;
>> };
>> template < class TRAITS >
>> struct foo {
>> static const unsigned x1 = TRAITS::v1;
>> static const unsigned x2 = TRAITS::v2;
>> };
>>
>> int main () {
>> foo<TRAITS<1,2>> f1;
>> // SET BREAKPOINT HERE
>> return 0;
>> }
>>
>> # Using g++ 7.3
>> $ g++ -g optimize_out.cpp
>>
>> # Using gdb 8.1
>> $ gdb a.out
>>
>> (gdb) break optimize_out.cpp:14
>> (gdb) r
>> (gdb) p f1
>> $1 = {static x1 = <optimized out>, static x2 = <optimized out>}
>>
>> Ok, looks good. Now traverse fields:
>>
>> (gdb) python
>>> f1 = gdb.parse_and_eval("f1")
>>> for field in f1.type.fields():
>>> print ("field name: ", field.name, "field type: ", field.type)
>>> field_val = f1[field]
>>> print ("optout?: ",field_val.is_optimized_out, "type:
>> ",field_val.type)
>>> end
>> field name: x1 field type: const unsigned int
>> optout?: True type: foo<TRAITS<1, 2> >
>> field name: x2 field type: const unsigned int
>> optout?: True type: foo<TRAITS<1, 2> >
>>
>>
>>
>> So type we get is foo<TRAITS<1, 2> >, not unsigned int.
>>
>> Looks like GDB-MI has same behavior. At least this code sample totatlly
>> confuses GDB GUI I use.
>>
>> Thanks,
>> Roman
>>
Hi Roman,
It just seems to be that we return a value with the type of the structure
instead of the type of the field in an error path somewhere. It causes
these weird behaviors in the CLI too:
(gdb) p f1
$1 = {static x1 = <optimized out>, static x2 = <optimized out>}
(gdb) p f1.x1
$2 = <optimized out>
(gdb) ptype f1.x1
type = struct foo<TRAITS<1, 2> > [with TRAITS = TRAITS<1, 2>] {
static const unsigned int x1;
static const unsigned int x2;
}
(gdb) ptype f1.x1.x1
type = struct foo<TRAITS<1, 2> > [with TRAITS = TRAITS<1, 2>] {
static const unsigned int x1;
static const unsigned int x2;
}
(gdb) p f1.x1.x1.x1.x1
$3 = <optimized out>
Can you try the patch below? I did not run the testsuite on it.
From ef7f73557e291ed2d8bc7f175765bdbb91e2c817 Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@polymtl.ca>
Date: Mon, 5 Feb 2018 00:34:08 -0500
Subject: [PATCH] Return right type in value_static_field
---
gdb/value.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/gdb/value.c b/gdb/value.c
index 9a144fb7fb..063f57129a 100644
--- a/gdb/value.c
+++ b/gdb/value.c
@@ -2978,7 +2978,10 @@ value_static_field (struct type *type, int fieldno)
= lookup_minimal_symbol (phys_name, NULL, NULL);
if (!msym.minsym)
- return allocate_optimized_out_value (type);
+ {
+ struct type *field_type = TYPE_FIELD_TYPE (type, fieldno);
+ return allocate_optimized_out_value (field_type);
+ }
else
{
retval = value_at_lazy (TYPE_FIELD_TYPE (type, fieldno),
--
2.16.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: GDB returns wrong type when traversing optimized-out Fields
2018-02-05 5:39 ` Simon Marchi
@ 2018-02-05 6:20 ` Roman Popov
0 siblings, 0 replies; 4+ messages in thread
From: Roman Popov @ 2018-02-05 6:20 UTC (permalink / raw)
To: Simon Marchi; +Cc: gdb
Thanks Simon,
Your patch solves the issue for all of my clients!
-Roman
2018-02-04 21:39 GMT-08:00 Simon Marchi <simark@simark.ca>:
> On 2018-02-04 11:06 PM, Roman Popov wrote:
> > I apologize for code typo in previous email. Here is correct code sample:
> >
> > template <unsigned v1, unsigned v2>
> > struct TRAITS {
> > static const unsigned val1 = v1;
> > static const unsigned val2 = v2;
> > };
> > template < class TRAITS >
> > struct foo {
> > static const unsigned x1 = TRAITS::val1;
> > static const unsigned x2 = TRAITS::val2;
> > };
> >
> > int main () {
> > foo<TRAITS<1,2>> f1;
> > // SET BREAKPOINT HERE
> > return 0;
> > }
> >
> > -Roman
> >
> >
> > 2018-02-04 20:02 GMT-08:00 Roman Popov <ripopov@gmail.com>:
> >
> >> Hi all,
> >> I've encountered strange GDB behavior when requesting a value of
> >> optimized-away field.
> >> Instead of returning None or raising exception, GDB returns an
> >> optimizied-out value of wrong type.
> >>
> >> Here is a small reproducer *optimize_out.cpp*:
> >>
> >> template <unsigned v1, unsigned v2>
> >> struct TRAITS {
> >> static const unsigned val1 = v1;
> >> static const unsigned val2 = v2;
> >> };
> >> template < class TRAITS >
> >> struct foo {
> >> static const unsigned x1 = TRAITS::v1;
> >> static const unsigned x2 = TRAITS::v2;
> >> };
> >>
> >> int main () {
> >> foo<TRAITS<1,2>> f1;
> >> // SET BREAKPOINT HERE
> >> return 0;
> >> }
> >>
> >> # Using g++ 7.3
> >> $ g++ -g optimize_out.cpp
> >>
> >> # Using gdb 8.1
> >> $ gdb a.out
> >>
> >> (gdb) break optimize_out.cpp:14
> >> (gdb) r
> >> (gdb) p f1
> >> $1 = {static x1 = <optimized out>, static x2 = <optimized out>}
> >>
> >> Ok, looks good. Now traverse fields:
> >>
> >> (gdb) python
> >>> f1 = gdb.parse_and_eval("f1")
> >>> for field in f1.type.fields():
> >>> print ("field name: ", field.name, "field type: ", field.type)
> >>> field_val = f1[field]
> >>> print ("optout?: ",field_val.is_optimized_out, "type:
> >> ",field_val.type)
> >>> end
> >> field name: x1 field type: const unsigned int
> >> optout?: True type: foo<TRAITS<1, 2> >
> >> field name: x2 field type: const unsigned int
> >> optout?: True type: foo<TRAITS<1, 2> >
> >>
> >>
> >>
> >> So type we get is foo<TRAITS<1, 2> >, not unsigned int.
> >>
> >> Looks like GDB-MI has same behavior. At least this code sample totatlly
> >> confuses GDB GUI I use.
> >>
> >> Thanks,
> >> Roman
> >>
>
> Hi Roman,
>
> It just seems to be that we return a value with the type of the structure
> instead of the type of the field in an error path somewhere. It causes
> these weird behaviors in the CLI too:
>
> (gdb) p f1
> $1 = {static x1 = <optimized out>, static x2 = <optimized out>}
> (gdb) p f1.x1
> $2 = <optimized out>
> (gdb) ptype f1.x1
> type = struct foo<TRAITS<1, 2> > [with TRAITS = TRAITS<1, 2>] {
> static const unsigned int x1;
> static const unsigned int x2;
> }
> (gdb) ptype f1.x1.x1
> type = struct foo<TRAITS<1, 2> > [with TRAITS = TRAITS<1, 2>] {
> static const unsigned int x1;
> static const unsigned int x2;
> }
> (gdb) p f1.x1.x1.x1.x1
> $3 = <optimized out>
>
> Can you try the patch below? I did not run the testsuite on it.
>
>
> From ef7f73557e291ed2d8bc7f175765bdbb91e2c817 Mon Sep 17 00:00:00 2001
> From: Simon Marchi <simon.marchi@polymtl.ca>
> Date: Mon, 5 Feb 2018 00:34:08 -0500
> Subject: [PATCH] Return right type in value_static_field
>
> ---
> gdb/value.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/gdb/value.c b/gdb/value.c
> index 9a144fb7fb..063f57129a 100644
> --- a/gdb/value.c
> +++ b/gdb/value.c
> @@ -2978,7 +2978,10 @@ value_static_field (struct type *type, int fieldno)
> = lookup_minimal_symbol (phys_name, NULL, NULL);
>
> if (!msym.minsym)
> - return allocate_optimized_out_value (type);
> + {
> + struct type *field_type = TYPE_FIELD_TYPE (type, fieldno);
> + return allocate_optimized_out_value (field_type);
> + }
> else
> {
> retval = value_at_lazy (TYPE_FIELD_TYPE (type, fieldno),
> --
> 2.16.1
>
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2018-02-05 4:02 GDB returns wrong type when traversing optimized-out Fields Roman Popov
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