gdb and newer versions of compilers

gdb and newer versions of compilers

[David Shrader]

Hello,

I have a user that is claiming gdb 7.2 does not work with C++ code 
compiled with GCC 4.8.2. Gdb is provided by the system (RHEL 6) while 
the compiler is one that I have provided. I'm still working with the 
user on possible errors in their workflow with gdb, but I wanted to 
investigate the limits of gdb's ability to keep working with binaries 
compiled by newer compilers because I really don't know. What kind of 
changes in a compiler would cause a particular version of gdb to no 
longer work correctly with it? For example, I know that a change in 
library format would probably require a new version of gdb, but does a 
change in C++ specs require the same treatment?

I know that running with the latest version of gdb is a good idea to get 
passed bugs and to net new features, but I'm trying to gain some sort of 
intuition as to when a new version of gdb is necessary rather than just 
a good idea.

Thank you all for your time and any help,
David

-- 
David Shrader
HPC-3 High Performance Computer Systems
Los Alamos National Lab
Email: dshrader <at> lanl.gov

Re: gdb and newer versions of compilers

[Eli Zaretskii]

> Date: Thu, 30 Apr 2015 10:00:17 -0600
> From: David Shrader <dshrader@lanl.gov>
> 
> I have a user that is claiming gdb 7.2 does not work with C++ code 
> compiled with GCC 4.8.2. Gdb is provided by the system (RHEL 6) while 
> the compiler is one that I have provided. I'm still working with the 
> user on possible errors in their workflow with gdb, but I wanted to 
> investigate the limits of gdb's ability to keep working with binaries 
> compiled by newer compilers because I really don't know. What kind of 
> changes in a compiler would cause a particular version of gdb to no 
> longer work correctly with it? For example, I know that a change in 
> library format would probably require a new version of gdb, but does a 
> change in C++ specs require the same treatment?

C++ support in GDB becomes significantly better with each new release,
and 7.2 is really old.  So it's quite possible that GDB 7.2 will not
be good enough for C++ debugging, certainly not as good as 7.9, the
latest released version.

> I know that running with the latest version of gdb is a good idea to get 
> passed bugs and to net new features, but I'm trying to gain some sort of 
> intuition as to when a new version of gdb is necessary rather than just 
> a good idea.

It is, specifically for C++ debugging.  Also, newer versions of GDB
support newer versions of DWARF debug info, so your user could use the
"-gdwarf-4 -g3" compiler options to get better debugging information
available to GDB.

Re: gdb and newer versions of compilers

[David Shrader]

Thank you for the information, Eli. I'll try the latest version with the 
user.

Thank you again,
David

On 04/30/2015 10:24 AM, Eli Zaretskii wrote:
>> Date: Thu, 30 Apr 2015 10:00:17 -0600
>> From: David Shrader <dshrader@lanl.gov>
>>
>> I have a user that is claiming gdb 7.2 does not work with C++ code
>> compiled with GCC 4.8.2. Gdb is provided by the system (RHEL 6) while
>> the compiler is one that I have provided. I'm still working with the
>> user on possible errors in their workflow with gdb, but I wanted to
>> investigate the limits of gdb's ability to keep working with binaries
>> compiled by newer compilers because I really don't know. What kind of
>> changes in a compiler would cause a particular version of gdb to no
>> longer work correctly with it? For example, I know that a change in
>> library format would probably require a new version of gdb, but does a
>> change in C++ specs require the same treatment?
> C++ support in GDB becomes significantly better with each new release,
> and 7.2 is really old.  So it's quite possible that GDB 7.2 will not
> be good enough for C++ debugging, certainly not as good as 7.9, the
> latest released version.
>
>> I know that running with the latest version of gdb is a good idea to get
>> passed bugs and to net new features, but I'm trying to gain some sort of
>> intuition as to when a new version of gdb is necessary rather than just
>> a good idea.
> It is, specifically for C++ debugging.  Also, newer versions of GDB
> support newer versions of DWARF debug info, so your user could use the
> "-gdwarf-4 -g3" compiler options to get better debugging information
> available to GDB.

-- 
David Shrader
HPC-3 High Performance Computer Systems
Los Alamos National Lab
Email: dshrader <at> lanl.gov