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Re: [GOLD] How can I add a undefined symbol in target implementation, not by "-u SYM" from command line ?
On Mon, Aug 13, 2012 at 8:30 PM, Jiong WANG <email@example.com> wrote:
> 2012/8/13 Ian Lance Taylor <firstname.lastname@example.org>:
>> On Mon, Aug 13, 2012 at 3:25 AM, Jiong WANG <email@example.com> wrote:
>>> How can I predefine a undefined symbol in target implementation?
>>> actually, I am porting gold for tilegx, and our arch's tls
>>> implementation requires predefiniation of "_tls_get_addr" because the
>>> assembler generate relocation which use this symbol implicitly.
>>> I know there are interfaces, "define_in_output_data/segment" to
>>> predefined symbol with value, but there is no interface to predefine
>>> "undefined" symbol ?
>>> gold linker do support this by command line "-u SYMBOL", but it's
>>> a compile time decision not link time.
>>> currently, I managed to support this by the following ugly code:
>>> options::parse_set(NULL, "_tls_get_addr",
>>> which is bad, so, could anyone give me some suggestion on this?
>> I assume that the symbol is defined somewhere. You probably want to
>> add a do_is_defined_by_abi method to your Target. See the examples in
>> existing targets.
> Hi Ian & all, thanks for your suggestion.
> I have explored do_is_defined_by_abi, and found it's mostly to avoid
> warning, but not for creating such a symbol
> do_is_defined_by_abi has one argument of the type "const Symbol*", so
> when it's invoked, that symbol should already existed.
> basically, I want to create a symbol which is neither against
> section or segment, just a normally external function symbol.
I'm sorry, I don't understand what you mean.
If there is no reference to __tls_get_addr in the object files, why do
you care whether it is defined?
If there is a reference in the object files, then where is it defined?
You seem to be asking how to create an undefined symbol, as though
used with the -u option. But that makes no sense. Why would you want
that? The purpose of the -u option is to add a reference to a symbol
in order to fetch the definition from an archive.