Re: [PATCH] s390: Implement 'type_align' gdbarch method

[Tom de Vries <tdevries@suse.de>]

On 08-08-19 13:40, Andreas Arnez wrote:
> The align.exp test case yields many FAILs on s390x, since GDB's _Alignoff
> doesn't always agree with the compiler's.  On s390x, the maximum alignment
> is 8, but GDB returns an alignment of 16 for 16-byte data types such as
> "long double".
> 
> This is fixed by implementing the type_align gdbarch method.  The new
> method returns an alignment of 8 for all integer, floating-point, and
> vector types larger than 8 bytes.  With this change, all align.exp tests
> pass.
> 

Hi,

in the "zSeries ELF Application Binary Interface Supplement" document I
find long double listed with 16-byte size and alignment.

Likewise in the "IBM XL C/C++ for Linux on z Systems Optimization and
Programming Guide".

So I wonder, is this patch hardcoding the assumptions of a single
compiler implementation (gcc) in gdb, thereby possibly breaking
functionality in gdb when debugging executables generated by other
compilers?

If so, ISTM the correct way to fix this is to get gcc to emit the
non-standard type alignment in the debug info.

Thanks,
- Tom