[Bug c/86092] New: global constant pointer optimization

[srinivas.sundar at vvdntech dot in]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86092

            Bug ID: 86092
           Summary: global constant pointer optimization
           Product: gcc
           Version: 5.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: srinivas.sundar at vvdntech dot in
  Target Milestone: ---

Here is my sample kernel code. which works fine in gcc-4, had an issue with
gcc-5. I get both the print even if I allocate the dynamic memory to
kern_buff_p.
Disassemble of code gives the constant variable is optimized in the If
statement. Can you provide me any FLAG to disable this optimization with this
constant pointers.


static char*  const kern_buff_p;

static int __init hello_start(void)
{

 if(!kern_buff_p)
        printk(KERN_INFO "buffer is NULL for first time \n");

  *((char**)(unsigned long
int)((&kern_buff_p)))=kmalloc(KERN_BUF_SIZE,GFP_KERNEL);

 if(!kern_buff_p)
        printk(KERN_INFO "buffer is NULL for second time \n");
}