Le 10/02/2012 21:32, Mike Frysinger a écrit :
On Friday 10 February 2012 14:39:12 Albert ARIBAUD wrote:
Le 07/02/2012 16:20, Mike Frysinger a écrit :
On Monday 06 February 2012 16:01:56 Albert ARIBAUD wrote:
Le 06/02/2012 21:57, Mike Frysinger a écrit :
Is there a keep attribute like the linker has for sections?
yes, __attribute__((used))
What is the point in adding a 'static' qualifier and a ((used))
attribute, when not adding them in the first place gives the same
result?
to control the visibility
I don't understand what you mean with this. Can you please elaborate?
no static means it has global elf visibility (other .c files can "extern" it,
and you have to worry about symbol clashes):
$ gcc -x c -c - -o test.o<<<'int foo;'&& readelf -s test.o | grep foo
7: 0000000000000004 4 OBJECT GLOBAL DEFAULT COM foo
static means it has local elf visibility (other files don't get access, and you
don't have to worry about symbol clashes):
$ gcc -x c -c - -o test.o<<<'static int foo;'&& readelf -s test.o | grep foo
5: 0000000000000000 4 OBJECT LOCAL DEFAULT 3 foo
imo, anything that should not be externally accessed should have "static".
this is just good programming practice.
I would agree 100% if the symbol was truly local, i.e. declared *and
used* locally. Here, however, it is used globally, by being gathered in
a global section to serve as an entry in a global array.
The only interest of making the symbol static would indeed be to allow
reusing the symbol name elsewhere, which I think is quite improbable
considering the symbol was global so far.
So we add the static qualifier despite the object actually not being
static; and because the object is not actually static, that qualifier
causes a legit diagnostic; and to eliminate that diagnostic, we add an
'unused' attribute. This I find less than good programming practice.
-mike
Amicalement,
--
Albert.
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