perl script for struct offsets etc

[RDBrown at mira dot net]

The enclosed perl script generates a gdb command script from ptype output
that shows the byte offset, length in bytes and cumulative fill byte count
for each field of the class or structure.
Where class/structure ordering isn't imposed, the output could be used
to argue for an ordering that pushes alignment fill to the end or 
brings frequently referenced fields together for `better' cache usage.

Any scripting support added to gdb should be able to do something like this
directly.

501 /devel/spanopen/700 % gdb libff/librds.so
GNU gdb 19990928
Copyright 1998 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i686-pc-linux-gnu"...
(gdb) ptype sql_proccolinfo_t
type = class sql_proccolinfo_t {
  private:
    dh_i16_t dtor_flag;
    hm_hdl_t *hm_curhdl;
  public:
    slink sl;
    dh_u16_t pci_proccolid;
    procid_t pci_procid;
    tpe_rssid_t pci_rssid;
    char pci_col[36];
    char pci_datatype[36];
    typeid_t pci_typeid;
    sql_proccoltype_t pci_coltype;
    dh_i32_t pci_width;
    dh_i32_t pci_scale;
    dh_boolean pci_nonull;
    sql_dflt_t pci_dflttp;
    dh_char_t *pci_default;

    sql_proccolinfo_t & operator=(sql_proccolinfo_t const &);
    sql_proccolinfo_t(sql_proccolinfo_t const &);
    static void * operator new(unsigned int);
    static void * operator new(unsigned int, hm_hdl_t *);
    static void operator delete(void *);
    sql_proccolinfo_t(alloctype_t);
    sql_proccolinfo_t(hm_hdl_t *, alloctype_t);
    ~sql_proccolinfo_t(void);
}
(gdb) shell	# xterm cut & paste
501 /devel/spanopen/700 % perl gdboff.pl > gdb.proccolinfo_t <<EOF
> type = class sql_proccolinfo_t {
>   private:
>     dh_i16_t dtor_flag;
>     hm_hdl_t *hm_curhdl;
>   public:
>     slink sl;
>     dh_u16_t pci_proccolid;
>     procid_t pci_procid;
>     tpe_rssid_t pci_rssid;
>     char pci_col[36];
>     char pci_datatype[36];
>     typeid_t pci_typeid;
>     sql_proccoltype_t pci_coltype;
>     dh_i32_t pci_width;
>     dh_i32_t pci_scale;
>     dh_boolean pci_nonull;
>     sql_dflt_t pci_dflttp;
>     dh_char_t *pci_default;
> 
>     sql_proccolinfo_t & operator=(sql_proccolinfo_t const &);
>     sql_proccolinfo_t(sql_proccolinfo_t const &);
>     static void * operator new(unsigned int);
>     static void * operator new(unsigned int, hm_hdl_t *);
>     static void operator delete(void *);
>     sql_proccolinfo_t(alloctype_t);
>     sql_proccolinfo_t(hm_hdl_t *, alloctype_t);
>     ~sql_proccolinfo_t(void);
> }
> EOF
502 /devel/spanopen/700 % exit	# Leading `>'-s from bash.
exit
(gdb) source gdb.proccolinfo_t
sizeof(sql_proccolinfo_t)	128
sql_proccolinfo_t.dtor_flag	0	2	0
sql_proccolinfo_t.hm_curhdl	4	4	2
sql_proccolinfo_t.sl	8	8	2
sql_proccolinfo_t.pci_proccolid	16	2	2
sql_proccolinfo_t.pci_procid	20	4	4
sql_proccolinfo_t.pci_rssid	24	4	4
sql_proccolinfo_t.pci_col	28	36	4
sql_proccolinfo_t.pci_datatype	64	36	4
sql_proccolinfo_t.pci_typeid	100	4	4
sql_proccolinfo_t.pci_coltype	104	4	4
sql_proccolinfo_t.pci_width	108	4	4
sql_proccolinfo_t.pci_scale	112	4	4
sql_proccolinfo_t.pci_nonull	116	1	4
sql_proccolinfo_t.pci_dflttp	120	4	7
sql_proccolinfo_t.pci_default	124	4	7
(gdb) q
502 /devel/spanopen/700 % exit


# Generate a gdb script to display offset, length and cumulative fill bytes
# for each field of a class or struct,
# from the gdb ptype output of the class or struct.
# eg
#sizeof(xyz)	128
#xyz.dtor_flag	0	2	0
#xyz.hm_curhdl	4	4	2
# ...
while (<>) {
    if (/^type = (?:class|struct) (\w+) {\s*$/) {
	$the_type = $1;
	printf "printf \"sizeof(%s)\\t%%d\\n\", sizeof(%s)\n",
	    $the_type, $the_type;
	printf "set variable \$cumlen = 0\n";
    }
    if (defined($the_type)) {
	if (/^}\s*$/) {
	    undef $the_type;
	}
	elsif (/^(?:|  p(?:rivate|public):)\s*$/) {
	}
	elsif (/ \**(\w+)(?:|\[\d+\]);\s*$/) {
	    my($the_field) = $1;
	    printf  "set variable \$offset = (int)(&(((%s *)0)->%s))\nset variable \$fieldlen = sizeof(((%s *)0)->%s)\nprintf \"%s.%s\\t%%d\\t%%d\\t%%d\\n\", \$offset, \$fieldlen, \$offset - \$cumlen\nset variable \$cumlen += \$fieldlen\n",
		$the_type, $the_field, $the_type, $the_field,
		$the_type, $the_field;
	}
	elsif (/(?:[^; ]|\);)\s*$/) {
	}
    }
}