bug#39962: 27.0.90; Crash in Emacs 27.0.90

[Paul Eggert]

On 3/8/20 1:34 AM, Pieter van Oostrum wrote:
> (gdb) p (char *)lispsym
> $34 = 0x198 <error: Cannot access memory at address 0x198>
> (gdb) p (char *)&lispsym[0]
> 'lispsym' has unknown type; cast it to its declared type

lispsym's type is not known?! Either your compiler or your debugger has got a 
serious bug.

What does this command do?

(gdb) p (char *) &lispsym

Also, what does 'objdump -g emacs.o' say about lispsym? Mine says this:

emacs.o:     file format elf64-x86-64

Contents of the .debug_info section:

  Compilation Unit @ offset 0x0:
   Length:        0x1a196 (32-bit)
   Version:       4
   Abbrev Offset: 0x0
   Pointer Size:  8
 ...
 <1><8c7>: Abbrev Number: 70 (DW_TAG_structure_type)
    <8c8>   DW_AT_name        : (indirect string, offset: 0xcb81d): Lisp_Symbol
    <8cc>   DW_AT_byte_size   : 48
    <8cd>   DW_AT_alignment   : 8
    <8ce>   DW_AT_decl_file   : 4
    <8cf>   DW_AT_decl_line   : 805
    <8d1>   DW_AT_sibling     : <0x8e2>
 ...
 <1><8e2>: Abbrev Number: 8 (DW_TAG_pointer_type)
    <8e3>   DW_AT_byte_size   : 8
    <8e4>   DW_AT_type        : <0x8c7>
 ...
 <1><2969>: Abbrev Number: 122 (DW_TAG_array_type)
    <296a>   DW_AT_type        : <0x8c7>
    <296e>   DW_AT_alignment   : 8
    <296f>   DW_AT_sibling     : <0x297b>
 <2><2973>: Abbrev Number: 96 (DW_TAG_subrange_type)
    <2974>   DW_AT_type        : <0x2d>
    <2978>   DW_AT_upper_bound : 1279
 <2><297a>: Abbrev Number: 0
 <1><297b>: Abbrev Number: 9 (DW_TAG_variable)
    <297c>   DW_AT_name        : (indirect string, offset: 0x3c788): lispsym
    <2980>   DW_AT_decl_file   : 29
    <2981>   DW_AT_decl_line   : 1170
    <2983>   DW_AT_type        : <0x2969>
    <2987>   DW_AT_external    : 1
    <2987>   DW_AT_declaration : 1
 ...