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

Simon Marchi simon.marchi@polymtl.ca
Wed Feb 7 16:36:00 GMT 2018


On 2018-02-07 11:26, Michael Matz wrote:
> 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).

But do struct/classes have mangled names?

Simon



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