[gentoo-user] [OFF TOPIC] Qt Creator unable to access containers in debug mode

[gentoo-user] [OFF TOPIC] Qt Creator unable to access containers in debug mode

[Francisco Ares]

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Hi,

Recently - but can't figure out exactly when - Qt Creator has become unable
to access Qt containers (where the STL ones work as expected) on the debug
panel.  It shows <not accessible> in place of the expected item quantity
for a QList, for instance, but for a std::vector<std::string>, it works,
allowing inspection of all items.

Any hints on what I may be doing wrong? The headers are all accessible, for
instance. Should I build Qt with debug symbols enabled, as recommended for
glibc?

Using current Qt 4.8.5, Qt Creator 2.8.1, gdb 7.7.1, gcc 4.8.3

Thanks!
Francisco

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[gentoo-user] Re: [OFF TOPIC] Qt Creator unable to access containers in debug mode

[Nikos Chantziaras]

On 24/03/15 15:07, Francisco Ares wrote:
> Hi,
>
> Recently - but can't figure out exactly when - Qt Creator has become
> unable to access Qt containers (where the STL ones work as expected) on
> the debug panel.  It shows <not accessible> in place of the expected
> item quantity for a QList, for instance, but for a
> std::vector<std::string>, it works, allowing inspection of all items.
>
> Any hints on what I may be doing wrong? The headers are all accessible,
> for instance. Should I build Qt with debug symbols enabled, as
> recommended for glibc?
>
> Using current Qt 4.8.5, Qt Creator 2.8.1, gdb 7.7.1, gcc 4.8.3

I remember having a problem with old Creator that had to do with showing 
contents of variables. I don't remember the details though. I only 
remember that the issue was gdb. I was using a version that was not 
working correctly with Creator 2.8. I had to downgrade to an old gdb. 
7.5.1, I think.

I can't reproduce the problem anymore, since I've since switched to 
Creator 3 (now on 3.3.2.) This is rather easy to upgrade to now, as Qt5 
is now in portage (although in ~arch.) If you want to upgrade, note that 
you can still develop for Qt4 just fine. Qt5 is only used to run Creator 
itself, it doesn't have any effect on the version of Qt you want to 
develop for.

Re: [gentoo-user] Re: [OFF TOPIC] Qt Creator unable to access containers in debug mode

[Francisco Ares]

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Thank you, gonna play a bit around  gdb.

Best regards,
Francisco

2015-03-24 10:52 GMT-03:00 Nikos Chantziaras <realnc@gmail.com>:

> On 24/03/15 15:07, Francisco Ares wrote:
>
>> Hi,
>>
>> Recently - but can't figure out exactly when - Qt Creator has become
>> unable to access Qt containers (where the STL ones work as expected) on
>> the debug panel.  It shows <not accessible> in place of the expected
>> item quantity for a QList, for instance, but for a
>> std::vector<std::string>, it works, allowing inspection of all items.
>>
>> Any hints on what I may be doing wrong? The headers are all accessible,
>> for instance. Should I build Qt with debug symbols enabled, as
>> recommended for glibc?
>>
>> Using current Qt 4.8.5, Qt Creator 2.8.1, gdb 7.7.1, gcc 4.8.3
>>
>
> I remember having a problem with old Creator that had to do with showing
> contents of variables. I don't remember the details though. I only remember
> that the issue was gdb. I was using a version that was not working
> correctly with Creator 2.8. I had to downgrade to an old gdb. 7.5.1, I
> think.
>
> I can't reproduce the problem anymore, since I've since switched to
> Creator 3 (now on 3.3.2.) This is rather easy to upgrade to now, as Qt5 is
> now in portage (although in ~arch.) If you want to upgrade, note that you
> can still develop for Qt4 just fine. Qt5 is only used to run Creator
> itself, it doesn't have any effect on the version of Qt you want to develop
> for.
>
>
>

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Re: [gentoo-user] [OFF TOPIC] Qt Creator unable to access containers in debug mode

[Fernando Rodriguez]

On Tuesday, March 24, 2015 10:07:56 AM Francisco Ares wrote:
> Hi,
> 
> Recently - but can't figure out exactly when - Qt Creator has become unable
> to access Qt containers (where the STL ones work as expected) on the debug
> panel.  It shows <not accessible> in place of the expected item quantity
> for a QList, for instance, but for a std::vector<std::string>, it works,
> allowing inspection of all items.
> 
> Any hints on what I may be doing wrong? The headers are all accessible, for
> instance. Should I build Qt with debug symbols enabled, as recommended for
> glibc?
> 
> Using current Qt 4.8.5, Qt Creator 2.8.1, gdb 7.7.1, gcc 4.8.3
> 
> Thanks!
> Francisco

Try to print it from gdb cli, if it works you'll know the issue QtCreator, 
otherwise you're likely missing some symbols. You should always compile any 
development libraries with debug symbols.

-- 
Fernando Rodriguez

[gentoo-user] Re: [OFF TOPIC] Qt Creator unable to access containers in debug mode

[Nikos Chantziaras]

On 24/03/15 21:12, Fernando Rodriguez wrote:
> On Tuesday, March 24, 2015 10:07:56 AM Francisco Ares wrote:
>> Hi,
>>
>> Recently - but can't figure out exactly when - Qt Creator has become unable
>> to access Qt containers (where the STL ones work as expected) on the debug
>> panel.  It shows <not accessible> in place of the expected item quantity
>> for a QList, for instance, but for a std::vector<std::string>, it works,
>> allowing inspection of all items.
>>
>> Any hints on what I may be doing wrong? The headers are all accessible, for
>> instance. Should I build Qt with debug symbols enabled, as recommended for
>> glibc?
>>
>> Using current Qt 4.8.5, Qt Creator 2.8.1, gdb 7.7.1, gcc 4.8.3
>>
>> Thanks!
>> Francisco
>
> Try to print it from gdb cli, if it works you'll know the issue QtCreator,
> otherwise you're likely missing some symbols. You should always compile any
> development libraries with debug symbols.

You don't need debug symbols for inspecting containers. They are not 
needed. The only reason for enabling debug symbols in Qt is if you want 
to step into Qt's code.

Re: [gentoo-user] Re: [OFF TOPIC] Qt Creator unable to access containers in debug mode

[Fernando Rodriguez]

On Tuesday, March 24, 2015 9:32:07 PM Nikos Chantziaras wrote:
> On 24/03/15 21:12, Fernando Rodriguez wrote:
> > On Tuesday, March 24, 2015 10:07:56 AM Francisco Ares wrote:
> >> Hi,
> >>
> >> Recently - but can't figure out exactly when - Qt Creator has become 
unable
> >> to access Qt containers (where the STL ones work as expected) on the 
debug
> >> panel.  It shows <not accessible> in place of the expected item quantity
> >> for a QList, for instance, but for a std::vector<std::string>, it works,
> >> allowing inspection of all items.
> >>
> >> Any hints on what I may be doing wrong? The headers are all accessible, 
for
> >> instance. Should I build Qt with debug symbols enabled, as recommended 
for
> >> glibc?
> >>
> >> Using current Qt 4.8.5, Qt Creator 2.8.1, gdb 7.7.1, gcc 4.8.3
> >>
> >> Thanks!
> >> Francisco
> >
> > Try to print it from gdb cli, if it works you'll know the issue QtCreator,
> > otherwise you're likely missing some symbols. You should always compile 
any
> > development libraries with debug symbols.
> 
> You don't need debug symbols for inspecting containers. They are not 
> needed. The only reason for enabling debug symbols in Qt is if you want 
> to step into Qt's code.

Thank you. You do need symbols though, just not Qts for this specific case. 
There are many reasons why you should compile your development libraries with 
symbols besides stepping into the code. Such as getting a backtrace. Even 
proprietary (closed-source) libraries often make the symbols available for 
this reason.

-- 
Fernando Rodriguez

Re: [gentoo-user] Re: [OFF TOPIC] Qt Creator unable to access containers in debug mode

[Francisco Ares]

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Thank you all for those clues, pretty interesting.

For now I suppose it is a gdb thing, as QtCreator is able to show details
about STL containers as expected.

Going to fiddle in gdb a bit more...


2015-03-24 17:07 GMT-03:00 Fernando Rodriguez <
frodriguez.developer@outlook.com>:

> On Tuesday, March 24, 2015 9:32:07 PM Nikos Chantziaras wrote:
> > On 24/03/15 21:12, Fernando Rodriguez wrote:
> > > On Tuesday, March 24, 2015 10:07:56 AM Francisco Ares wrote:
> > >> Hi,
> > >>
> > >> Recently - but can't figure out exactly when - Qt Creator has become
> unable
> > >> to access Qt containers (where the STL ones work as expected) on the
> debug
> > >> panel.  It shows <not accessible> in place of the expected item
> quantity
> > >> for a QList, for instance, but for a std::vector<std::string>, it
> works,
> > >> allowing inspection of all items.
> > >>
> > >> Any hints on what I may be doing wrong? The headers are all
> accessible,
> for
> > >> instance. Should I build Qt with debug symbols enabled, as recommended
> for
> > >> glibc?
> > >>
> > >> Using current Qt 4.8.5, Qt Creator 2.8.1, gdb 7.7.1, gcc 4.8.3
> > >>
> > >> Thanks!
> > >> Francisco
> > >
> > > Try to print it from gdb cli, if it works you'll know the issue
> QtCreator,
> > > otherwise you're likely missing some symbols. You should always compile
> any
> > > development libraries with debug symbols.
> >
> > You don't need debug symbols for inspecting containers. They are not
> > needed. The only reason for enabling debug symbols in Qt is if you want
> > to step into Qt's code.
>
> Thank you. You do need symbols though, just not Qts for this specific case.
> There are many reasons why you should compile your development libraries
> with
> symbols besides stepping into the code. Such as getting a backtrace. Even
> proprietary (closed-source) libraries often make the symbols available for
> this reason.
>
> --
> Fernando Rodriguez
>
>

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[gentoo-user] Re: [OFF TOPIC] Qt Creator unable to access containers in debug mode

[Nikos Chantziaras]

Note that gdb cannot inspect containers. It doesn't know anything about 
them.

Qt Creator uses "debugging helpers" for that. See:

   https://qt-project.org/doc/qtcreator-2.8/creator-debugging-helpers.html

Since you're using a deprecated version of Creator (2.8 is from 2013 and 
not maintained anymore), those helpers are probably not updated for new 
gdb versions.

If you don't want to upgrade Creator through portage, you could instead 
use the binary Qt Creator installer, and simply install it in your home 
directory (I did that in the past, before Qt5 was put in ~arch.)


On 24/03/15 22:43, Francisco Ares wrote:
> Thank you all for those clues, pretty interesting.
>
> For now I suppose it is a gdb thing, as QtCreator is able to show
> details about STL containers as expected.
>
> Going to fiddle in gdb a bit more...
>
>
> 2015-03-24 17:07 GMT-03:00 Fernando Rodriguez
> <frodriguez.developer@outlook.com
> <mailto:frodriguez.developer@outlook.com>>:
>
>     On Tuesday, March 24, 2015 9:32:07 PM Nikos Chantziaras wrote:
>      > On 24/03/15 21:12, Fernando Rodriguez wrote:
>      > > On Tuesday, March 24, 2015 10:07:56 AM Francisco Ares wrote:
>      > >> Hi,
>      > >>
>      > >> Recently - but can't figure out exactly when - Qt Creator has
>     become
>     unable
>      > >> to access Qt containers (where the STL ones work as expected)
>     on the
>     debug
>      > >> panel.  It shows <not accessible> in place of the expected
>     item quantity
>      > >> for a QList, for instance, but for a std::vector<std::string>,
>     it works,
>      > >> allowing inspection of all items.
>      > >>
>      > >> Any hints on what I may be doing wrong? The headers are all
>     accessible,
>     for
>      > >> instance. Should I build Qt with debug symbols enabled, as
>     recommended
>     for
>      > >> glibc?
>      > >>
>      > >> Using current Qt 4.8.5, Qt Creator 2.8.1, gdb 7.7.1, gcc 4.8.3
>      > >>
>      > >> Thanks!
>      > >> Francisco
>      > >
>      > > Try to print it from gdb cli, if it works you'll know the issue
>     QtCreator,
>      > > otherwise you're likely missing some symbols. You should always
>     compile
>     any
>      > > development libraries with debug symbols.
>      >
>      > You don't need debug symbols for inspecting containers. They are not
>      > needed. The only reason for enabling debug symbols in Qt is if
>     you want
>      > to step into Qt's code.
>
>     Thank you. You do need symbols though, just not Qts for this
>     specific case.
>     There are many reasons why you should compile your development
>     libraries with
>     symbols besides stepping into the code. Such as getting a backtrace.
>     Even
>     proprietary (closed-source) libraries often make the symbols
>     available for
>     this reason.

Re: [gentoo-user] Re: [OFF TOPIC] Qt Creator unable to access containers in debug mode

[Fernando Rodriguez]

On Wednesday, March 25, 2015 12:32:30 AM Nikos Chantziaras wrote:
> Note that gdb cannot inspect containers. It doesn't know anything about 
> them.

It can, it's just not pretty:

(gdb) p list1
$1 = {{p = {static shared_null = {ref = {_q_value = 15}, alloc = 0, begin = 0, 
end = 0, sharable = 1, array = {0x0}}, 
      d = 0x61b050}, d = 0x61b050}}
(gdb) p/c ((QString*)list1.d.array).d.data[0]@10
$2 = {72 'H', 101 'e', 108 'l', 108 'l', 111 'o', 32 ' ', 71 'G', 68 'D', 66 
'B', 0 '\000'}

and with missing symbols:

(gdb) p list1
No symbol "list1" in current context.

So I wasn't arguing, just suggesting a way to find out quickly.

-- 
Fernando Rodriguez