Questions about linking.

For example,there are two object files: a1.o and a2.o .
I think one object file shoud be composed of text segment,data segment
and bss segment.
Underside are the structure pictures of a1.o and a2.o:

|--------| |--------|
| bss1| |bss2 |
|--------| |--------|
|data1| |data2|
|--------| |--------|
|text1 | |text2 |
|--------| |--------|

If a1.o is linked with a2.o, and create the file a .
Which is the structure of a ?

|--------|
|bss2 | |---------|
|bss1 | | bss2 |
|--------| | data2|
|data2| | text2 |
|data1| |---------|
|--------| | bss1|
|text2 | | data1|
|text1 | | text1 |
|--------| |---------|

(1) (2)

Another question: For a library file, how the picture it is ?
Can you draw it for me?

Does Minix3.1.1 support dynamic linking?
(Supposeing it does) When one executeable is running, he want to
dynamically link a lib. Does someone can tell me how he do it?

Thanks.
Lxbcyllt.

Diagram (1) is how it is done. When an executable is loaded it is
allocated 2 segments in it's own LDT (5 in reality, but only 2 are
relevant). These are the text and data segment, stack and bss are
loaded into data segment. This segment must be of continuous memory so
having the parts all split up as is (2) wouldn't make sense at all.
-ivan

Ivan Kelly 写道：
[color=blue]
> Diagram (1) is how it is done.[/color]

If a1.o and a2.o are included in a liba.a,then the structure of liba.a
likes diagram (1) too.
Is right?

Thanks.
Lxbcyllt.

[email]lxbcyllt@jx163.com[/email] wrote:[color=blue]
> Ivan Kelly 写道：
>
> [color=green]
>>Diagram (1) is how it is done.[/color]
>
>
> If a1.o and a2.o are included in a liba.a,then the structure of liba.a
> likes diagram (1) too.
> Is right?
>
> Thanks.
> Lxbcyllt.
> [/color]

Minix 3 doesn't support dynamic linking; we don't even have a ld.so

Also, there is no virtual memory support, so memory is a issue.

> Minix 3 doesn't support dynamic linking; we don't even have a ld.so
Thanks for above help.

My other question is about static linking.

For example, if one library (i.e. liba.a) include two functions : f1( )
and f2( ), one object file which calls f1( ) is statically linked with
liba.a to get a executable, then is the f1( ) linked into the
executable or the whole liba.a ?

In other words, does the linker select the necessary stuff , not the
whole, to get the executable?
If so,is it applied to the LIB's global variables which are accessed by
a object file?

Are all the global variables which come from different object files
collected in the LIB's data segment by the linker ?

Thanks.
lxbcyllt.

[email]lxbcyllt@jx163.com[/email] wrote:[color=blue][color=green]
>> Minix 3 doesn't support dynamic linking; we don't even have a ld.so[/color]
> Thanks for above help.
>
> My other question is about static linking.
>
> For example, if one library (i.e. liba.a) include two functions : f1( )
> and f2( ), one object file which calls f1( ) is statically linked with
> liba.a to get a executable, then is the f1( ) linked into the
> executable or the whole liba.a ?
>
> In other words, does the linker select the necessary stuff , not the
> whole, to get the executable?
> If so,is it applied to the LIB's global variables which are accessed by
> a object file?
>
> Are all the global variables which come from different object files
> collected in the LIB's data segment by the linker ?[/color]


Libraries are a collection of objects (archive of object files).
Each objects, usually but not necessarily, contains a function and data.
During the linking phase the linker searches the libraries for
unresolved symbols and when it finds them extracts a copy of the object
file which is then linked as any object file in input to the linker.

If a global variable is found in the library the relevant object file is
retrieved from the archive and linked.

Ciao
Giovanni
--
A computer is like an air conditioner,
it stops working when you open Windows.
Registered Linux user #337974 <http://counter.li.org/>