Re: gdb 8.x - g++ 7.x compatibility

[Simon Marchi <simon dot marchi at polymtl dot ca>]

On 2018-02-02 22:17, Roman Popov wrote:
> Hello,
> I'm trying to switch from g++ 5.4 to g++ 7.2.
> GDB 8.0.1 however does not understand RTTI generated by g++7.2, so my
> Python scripts for GDB are not working.
>
> Here is a code example:
>
> struct base {  virtual ~base(){}  };
>
> template< int IVAL, unsigned UVAL, unsigned long long ULLVAL>
> struct derived : base {
>     int x = IVAL + + UVAL + ULLVAL;
> };
>
> int main()
> {
>     base * o = new derived<1,2,3>{};
>     return 0;
> }
>
> When compiled with g++5.4 I can read value of x in debugger.
> When compiled with g++7.2   gdb reports:
> warning: RTTI symbol not found for class 'derived<1, 2u, 3ull>'
>
> Problem here is that type name saved in debug information is
> *derived<1, 2, 3>*, not *derived<1, 2u, 3ull>*
>
> Do you plan to fix this anytime soon?
>
> Thanks,
> Roman

Hi Roman,

Your problem is probably linked to these issues, if you want to follow 
them:

gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81932
gdb: https://sourceware.org/bugzilla/show_bug.cgi?id=22013

As Carl said, it's a good idea to try with the latest version of both 
tools, but I think the issue will still be present.

GCC changed how it outputs unsigned template parameters in the debug 
info (from 2u to just 2), and it doesn't look like it's going to change 
it back.  So I suppose we'll have to find a way to make GDB deal with 
it.

Simon