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

[Michael Matz <matz@suse.de>]

Hi,

On Wed, 7 Feb 2018, Simon Marchi wrote:

> This addresses the issue of how to do good software design in GDB to 
> support different producers cleanly, but I think we have some issues 
> even before that, like how to support g++ 7.3 and up.  I'll try to 
> summarize the issue quickly. It's now possible to end up with two 
> templated classes with the same name that differ only by the signedness 
> of their non-type template parameter.  One is Foo<int N> and the other 
> is Foo<unsigned int N> (the 10 is unsigned).  Until 7.3, g++ would 
> generate names like Foo<10> for the former and names like Foo<10u> for 
> the later (in the DW_AT_name attribute of the classes' DIEs). Since 7.3, 
> it produces Foo<10> for both.

Yeah, gdb needs a way to lookup types by name, and since the change 
DW_AT_name can't be used for this anymore.  Either that needs to be 
fixed/reverted, or we do the more obvious thing: since types in C++ have 
linkage it makes sense to add the linkage (i.e. mangled) name to the types 
DIE using the traditional DW_AT_MIPS_linkage_name.

That latter solution would have the advantage that you don't need to 
demangle anything anymore.  From vtable you get to typeinfo, from there 
for typeinfo name, and that contains the mangled type name (without _Z 
prefix).


Ciao,
Michael.