Re: [PATCH] [gdb/symtab] Workaround PR gas/31115

[Tom Tromey <tom@tromey.com>]

>>>>> "Tom" == Tom de Vries <tdevries@suse.de> writes:

Tom> This is a regression due to PR gas/31115, which makes gas produce a low_pc
Tom> with the thumb bit set (0x4d8 & 0x1):
Tom> ...
Tom>  <1><24>: Abbrev Number: 2 (DW_TAG_subprogram)
Tom>     <25>   DW_AT_name        : main
Tom>     <29>   DW_AT_external    : 1
Tom>     <29>   DW_AT_type        : <0x2f>
Tom>     <2a>   DW_AT_low_pc      : 0x4d9
Tom>     <2e>   DW_AT_high_pc     : 12
Tom> ...

Tom> The regression was introduced in 2.39, and is also present in 2.40 and 2.41,
Tom> and hasn't been fixed yet.

Tom> Work around this in read_func_scope, by using gdbarch_addr_bits_remove on
Tom> low_pc and high_pc.

Are there ever cases where this bit ought to be set here?

Tom>    lowpc = per_objfile->relocate (unrel_low);
Tom>    highpc = per_objfile->relocate (unrel_high);
 
Tom> +  if (gdbarch_bfd_arch_info (gdbarch)->arch == bfd_arch_arm
Tom> +      && producer_is_gas_ge_2_39 (cu))
Tom> +    {
Tom> +      /* Gas version 2.39 produces DWARF for a Thumb subprogram with a low_pc
Tom> +	 attribute with the thumb bit set (PR gas/31115).  Work around this.  */
Tom> +      lowpc = gdbarch_addr_bits_remove (gdbarch, lowpc);
Tom> +      highpc = gdbarch_addr_bits_remove (gdbarch, highpc);

'relocate' calls gdbarch_adjust_dwarf2_addr.  I wonder if that's a
better approach.

Right now there are a few gdbarch methods here and it's never been clear
to me why they are different or when one should be used or not.  That
is, there's also adjust_dwarf2_line, which is used in several other
spots -- except dwarf_record_line_1 which for some reason calls
gdbarch_addr_bits_remove.

Tom