Ah I think slowly understand. SYM_CLASS is more like “Eclipse, this thing here is data (SYM_CLASS_TYPE). Just so you know, it’s TYPE_CLASS_REAL
so don’t forget the comma!”
Okay I guess now this starts to make sense. The SYM_FLAG_* macros will then e.g. stand for things like typedefs, or structs.
But it’s still kinda hard for me to see how structs would really be “typed”..
I’m not that much into compilers which is why I understand all this some kind of slowly.. ^^
From: tcf-dev-bounces@xxxxxxxxxxx
[mailto:tcf-dev-bounces@xxxxxxxxxxx] On Behalf Of Kalle Hammarsten
Sent: Thursday, August 28, 2014 2:00 PM
To: TCF Development
Subject: Re: [tcf-dev] symbols.h
If you have a uint16_t type, that is a SYM_CLASS_TYPE with TYPE_CLASS_CARDINAL. A variable of that type is a SYM_CLASS_REFERENCE of the same TYPE_CLASS.
SYM_CLASS describes what kind of symbol it is, a function, a data type or a variable etc. Each SYM_CLASS can be of 1 or more different types.
As far as I know SYM_CLASS_FUNCTION is always of type TYPE_CLASS_FUNCTION, while a SYM_CLASS_TYPE or SYM_CLASS_REFERENCE can have a lot of different
types.
/Kalle H.
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.
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”?
_______________________________________________
tcf-dev mailing list
tcf-dev@xxxxxxxxxxx
To change your delivery options, retrieve your password, or unsubscribe from this list, visit
https://dev.eclipse.org/mailman/listinfo/tcf-dev
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.
