Hi all,

is there any way how to print a content of a D global variable in GDB ?
-- 
mk

On Saturday, 31 March 2012 at 14:58:48 UTC, Martin Krejcirik wrote:
> Hi all,
>
> is there any way how to print a content of a D global variable in GDB ?

Try in gdb:

p 'module_name.glob_var'

P.S. You can also use autocomplete: p 'module_name.<TAB><TAB>

> Try in gdb:
>
> p 'module_name.glob_var'


argh, the single quotes. Thanks, now it works if the global is declared shared.
But if it isn't, print shows just the init value, no changed data. Any idea ?

--
mk

On Mon, 02 Apr 2012 19:36:27 +0200, Martin Krejcirik <mk-junk@i-line.cz> wrote:

>> Try in gdb:
>>
>> p 'module_name.glob_var'
>
>
> argh, the single quotes. Thanks, now it works if the global is declared shared.
> But if it isn't, print shows just the init value, no changed data. Any idea ?
>
> --
> mk

Unless it's shared or __gshared, every thread gets it's own copy. D defaults to thread local storage (TLS).

On 2.4.2012 19:56, simendsjo wrote:
> Unless it's shared or __gshared, every thread gets it's own copy. D defaults to thread local storage (TLS).

I know but the problem is, that gdb doesn't show the changed value of TLS variable. Example:

import std.stdio;

shared int shrgl = 1;
int tlsgl = 10;

void main()
{
   writefln("%s %s", shrgl, tlsgl); // prints 1,10
   shrgl++; tlsgl++;
   writefln("%s %s", shrgl, tlsgl); // prints 2,11
==> gdb p 'tls.shrgl' ==> 2
==> gdb p 'tls.tlslg' ==> 10
}

--
mk

On Monday, 2 April 2012 at 22:24:36 UTC, Martin Krejcirik wrote:
> On 2.4.2012 19:56, simendsjo wrote:
>> Unless it's shared or __gshared, every thread gets it's own copy. D
>> defaults to thread local storage (TLS).
>
> I know but the problem is, that gdb doesn't show the changed value of
> TLS variable. Example:
>
> import std.stdio;
>
> shared int shrgl = 1;
> int tlsgl = 10;
>
> void main()
> {
>    writefln("%s %s", shrgl, tlsgl); // prints 1,10
>    shrgl++; tlsgl++;
>    writefln("%s %s", shrgl, tlsgl); // prints 2,11
> ==> gdb p 'tls.shrgl' ==> 2
> ==> gdb p 'tls.tlslg' ==> 10
> }
>
> --
> mk

Can't reproduce. With gdc and dmd-2.058 I have correct result. GDB-7.3

On Tue, 03 Apr 2012 07:47:40 +0200, Mihail Zenkov <mihail.zenkov@gmail.com> wrote:

> On Monday, 2 April 2012 at 22:24:36 UTC, Martin Krejcirik wrote:
>> On 2.4.2012 19:56, simendsjo wrote:
>>> Unless it's shared or __gshared, every thread gets it's own copy. D
>>> defaults to thread local storage (TLS).
>>
>> I know but the problem is, that gdb doesn't show the changed value of
>> TLS variable. Example:
>>
>> import std.stdio;
>>
>> shared int shrgl = 1;
>> int tlsgl = 10;
>>
>> void main()
>> {
>>    writefln("%s %s", shrgl, tlsgl); // prints 1,10
>>    shrgl++; tlsgl++;
>>    writefln("%s %s", shrgl, tlsgl); // prints 2,11
>> ==> gdb p 'tls.shrgl' ==> 2
>> ==> gdb p 'tls.tlslg' ==> 10
>> }
>>
>> --
>> mk
>
> Can't reproduce. With gdc and dmd-2.058 I have correct result. GDB-7.3

I cannot reproduce this on dmd-2.059 trunk either.

On 3.4.2012 9:40, simendsjo wrote:
>> Can't reproduce. With gdc and dmd-2.058 I have correct result. GDB-7.3
> I cannot reproduce this on dmd-2.059 trunk either.

Interesting. I'm using dmd 2.058 binary (.zip) on debian squeeze 32bit, gdb-minimal 7.3-1~bpo60+1 from backports. Even tried to compile gdb 7.4, but still the same behavior.

-- 
mk

On Wednesday, 4 April 2012 at 01:23:34 UTC, Martin Krejcirik wrote:
> On 3.4.2012 9:40, simendsjo wrote:
>>> Can't reproduce. With gdc and dmd-2.058 I have correct result. GDB-7.3
>> I cannot reproduce this on dmd-2.059 trunk either.
>
> Interesting. I'm using dmd 2.058 binary (.zip) on debian squeeze 32bit,
> gdb-minimal 7.3-1~bpo60+1 from backports. Even tried to compile gdb 7.4,
> but still the same behavior.

I also use dmd-2.058/linux/bin32/dmd.
1. Try compile without options, just 'dmd tls.d'
2. How you set break point in the end of program? Try add this hack:
int *p = null;
*p = 5;
It segfault you program and you can check  backtrace and variable state.

On Wednesday, 4 April 2012 at 07:01:39 UTC, Mihail Zenkov wrote:
> 1. Try compile without options, just 'dmd tls.d'

I'm not sure what that should accomplish, as I wouldn't get the debug info.

> 2. How you set break point in the end of program? Try add this

breakpoints are ok. In fact everything is ok, except it looks like that gdb is accessing (in print, set var) a "shadow" non-tls copy of my tls variable.

Consider this example:
import std.stdio;

__gshared int shrvar = 1;
int tlsvar = 5;

void main()
{
   writefln("%d %d | %#x %#x", shrvar, tlsvar, &shrvar, &tlsvar); // 1, 5
   shrvar++; tlsvar++;
   writefln("%d %d | %#x %#x", shrvar, tlsvar, &shrvar, &tlsvar); // gdb p 'tls.tlsvar' = 5
}

Now running GDB:

(gdb) b 10
Breakpoint 1 at 0x806b7ba: file tls.d, line 10.
(gdb) r
Starting program: /home/mk/dmd/tls
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/i686/cmov/libthread_db.so.1".
1 5 | 0x808f308 0xf7e466c8

Breakpoint 1, D main () at tls.d:10
10         writefln("%d %d | %#x %#x", shrvar, tlsvar, &shrvar, &tlsvar); // gdb p 'tls.tlslg' = 5
(gdb) n
2 6 | 0x808f308 0xf7e466c8
11      }
(gdb) info address tls.shrvar
Symbol "tls.shrvar()" is static storage at address 0x808f308.
(gdb) info address tls.tlsvar
Symbol "tls.tlsvar()" is static storage at address 0x808f004.
(gdb) x 0xf7e466c8
0xf7e466c8:     0x00000006
(gdb) x 0x808f004
0x808f004:      0x00000005

As you can see, the address of tlsvar in gdb is different then the one from writeln.

Trying similar C program in gdb, it correctly recognize the TLS variable:
(gdb) info address shrvar
Symbol "shrvar" is static storage at address 0x8049658.
(gdb) info address tlsvar
Symbol "tlsvar" is a thread-local variable at offset 0x0 in the thread-local storage for `/home/mk/dmd/glob'.

I read somwhere that it is necessary to link libpthread, not sure if that applies to DMD too, but it doesn't seem to have any effect anyway.