On Thu, Mar 26, 2020 at 7:03 PM Jim Wilson <jimw@xxxxxxxxxx> wrote:
>
> On Wed, Mar 25, 2020 at 6:41 PM William Tambe via Gcc-help
> <gcc-help@xxxxxxxxxxx> wrote:
> > Any idea what is causing GCC to generate the following symbols prefixed
> > with "call_" ?
> >
> > call___do_global_ctors_aux
> > call___do_global_dtors_aux
> > call_frame_dummy
>
> find . -type f | xargs grep do_global_ctors_aux
> on a linux machine in the gcc source tree will show you all uses of
> do_global_ctors_aux, there are only about a hundred of them, and most
> of them are obviously not relevant. You can ignore the ia64, pa, and
> ChangeLog file hits. That gives a couple dozen, of which the most
> interesting one is this one
> ./libgcc/crtstuff.c:CRT_CALL_STATIC_FUNCTION
> (__LIBGCC_INIT_SECTION_ASM_OP__, __do_global_ctors_aux)
Thanks for shedding the light; essentially CRT_CALL_STATIC_FUNCTION()
inserts functions calls into the section given as argument.
But there is a weird behavior I am seeing; CRT_CALL_STATIC_FUNCTION()
is defined as follow:
# define CRT_CALL_STATIC_FUNCTION(SECTION_OP, FUNC) \
static void __attribute__((__used__)) \
call_ ## FUNC (void) \
{ \
asm (SECTION_OP); \
FUNC (); \
FORCE_CODE_SECTION_ALIGN \
asm (__LIBGCC_TEXT_SECTION_ASM_OP__); \
}
When asm (__LIBGCC_TEXT_SECTION_ASM_OP__) is used, it is not necessary
the same section as before the use of asm (SECTION_OP); hence the
prologue instructions end up not showing in the dis-assembly of "call_
## FUNC" .
Any idea why asm (__LIBGCC_TEXT_SECTION_ASM_OP__) is used instead of
asm (".previous") to restore the section before the use of asm
(SECTION_OP) ?
I tried above and it seems to work; I can see the prologue
instructions correctly showing in the dis-assembly of "call_ ## FUNC".
>
> Jim
