[Bug ld/18379] New: .fini_array support brings in unused codes

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18379

            Bug ID: 18379
           Summary: .fini_array support brings in unused codes
           Product: binutils
           Version: 2.26 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: hjl.tools at gmail dot com
  Target Milestone: ---

To support .fini_array, linker always links in the .fini_array handler
even if it isn't used.  We can't mark the .fini_array handler weak since
it won't be called when it is used:

address@hidden fini]$ cat foo.c 
static void foo ( void ) __attribute__((destructor));

static int counter;

static void 
foo (void)
{
  counter++;
}
address@hidden fini]$ cat start.c 
extern void __libc_csu_fini (void)
#ifdef WEAK
__attribute__((weak))
#endif
;

void
_start ()
{
#ifdef WEAK
  if (__libc_csu_fini)
#endif
    __libc_csu_fini ();
}
address@hidden fini]$ cat fini.c 
#include <stdint.h>
#include <stddef.h>

extern void (*__fini_array_start[]) (void);
extern void (*__fini_array_end[]) (void);

static void
run_fini_arry (void *p)
{
  uintptr_t i = (uintptr_t) p;
  while (i-- > 0)
    (*__fini_array_start [i]) ();
}

extern void bar (void (*fn) (void *), void *arg, void *handle);

void
__libc_csu_fini (void)
{
  ptrdiff_t count = __fini_array_end - __fini_array_start;
  if (count)
    bar ((void (*) (void *)) run_fini_arry, (void *) count, NULL);
}
address@hidden fini]$ cat bar.S 
        .section .text.bar,"ax",@progbits
        .globl  bar
        .type   bar, @function
bar:
        .space 0x400000
        .size   bar, .-bar
address@hidden fini]$ make LD=ld
gcc  -O2 -g   -c -o start.o start.c
ld -o x start.o libbar.a
gcc  -O2 -g -DWEAK -c start.c -o startweak.o
gcc  -O2 -g -fpic   -c -o foo.o foo.c
ld -o xw startweak.o foo.o libbar.a
ld -o yw startweak.o libbar.a
ls -l x xw yw
-rwxrwxr-x 1 hjl hjl 4197928 May  5 12:59 x
-rwxrwxr-x 1 hjl hjl    2864 May  5 12:59 xw
-rwxrwxr-x 1 hjl hjl    1968 May  5 12:59 yw
address@hidden fini]$

-- 
You are receiving this mail because:
You are on the CC list for the bug.