Hi!
That makes all perfect sense to me. But unfortunately I don’t understand what a “symbol class” is.
What is the fundamental difference between a SYM_CLASS_FUNCTION and a TYPE_CLASS_FUNCTION?
int main() {}; // is main a SYM_CLASS_FUNCTION or TYPE_CLASS_FUNCTION?
int (*fnc_ptr)(void) = &main; // what about fnc_ptr? TYPE_CLASS _POINTER or _FUNCTION?
If SYM_CLASS_REFERENCE is the address of an object (variable) in memory where is the difference to TYPE_CLASS_POINTER?
You see, I really don’t get it what symbol classes are.
From: tcf-dev-bounces@xxxxxxxxxxx
[mailto:tcf-dev-bounces@xxxxxxxxxxx] On Behalf Of Kalle Hammarsten
Sent: Thursday, August 28, 2014 1:06 PM
To: TCF Development
Subject: Re: [tcf-dev] symbols.h
In symbols.h there are comments explaining the SYM_CLASS_* defines. SYM_CLASS_REFERENCE for instance means a variable.
The TYPE_CLASS_* defines are data type descriptions, the one needing explaining might be TYPE_CLASS_COMPOSITE that means a complex type like a
struct or union.
/Kalle H.
Hi Xavier!
Thanks for he fast reply! I already took a look at the windows implementation.
It is where I was starting and step by step adapted it to my version of the tcf-agent.
It is good that you took a function as example because this is already the point where I have my struggles.
SYM_CLASS_FUNCTION is said to be an address of a function. So when would I have to return this information?
I don’t understand what a symbol class and a type class is because this is confusing me a little.
Another thing is SYM_CLASS_REFERENCE and TYPE_CLASS_POINTER. As soon as I reached my aha-moment I think
I can do it without help but right now I’m a little stuck.
J
Thank you and best regards,
Stefan
Could someone explain to me a few things about the SYM_CLASS_* and TYPE_CLASS_* macros?
E.g. where do things like char, short, void struct, bit, bitfield fall into?
What would be a “cardinal class type”?
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Hi Stefan,
> E.g. where do things like char, short, void struct, bit, bitfield fall into?
Take a look at Dwarf3 specs, page 65.
(http://dwarfstd.org/doc/Dwarf3.pdf)
You'll got an AT_base_type with an encoding.
Depending of the encoding, you can have a boolean, an address.
(page 146).
symbols_elf.c / get_symbol_type_class will decypher a Symbol object to return it's class.
For instance, on linux, compile a program with debug info and do readelf -wi
<1><141>: Abbrev Number: 2 (DW_TAG_subprogram)
<142> DW_AT_external : 1
<143> DW_AT_name : (indirect string, offset: 0x169): usrRtpAppInit
<147> DW_AT_decl_file : 1
<148> DW_AT_decl_line : 25
<149> DW_AT_prototyped : 1
<14a> DW_AT_low_pc : 0x100044
<14e> DW_AT_high_pc : 0x100048
That describes a function. Look in get_symbol_type_class, it will convert the TAG_subprogram as TYPE_CLASS_FUNCTION.
Same logic applies for data types like ARRAY, ENUMERATION.
> What would be a “cardinal class type”?
get_symbol_type sees :
DW_ATE_unsigned_char unsigned (character) as cardinal.
I'm not 100% sure what a cardinal type means but cardinal is number used for counting.
Hope it helps a little,
Very Best Regards,
Xavier.
