[Dwarf-discuss] multiple entries for one line of code in .debug_line ?

[Jun Koi]

Hi Sebastian,

On 10/7/06, Sebastian Krawczuk <syk at ocsystems.com> wrote:
> Jun,
>
> All is fine.  Anything that your compiler emitted in rage 0xc01526c4
> and  0xc01526ea  is in reference to your 'return' statement at line
> 369.  Maybe the compiler broken it into atomic operations and had to
> produce such source line table.  I don't know.  I would not worry too
> much and just aggregate data from such entries and interpret is as one
> line entry and range 0xc01526c4-0xc01526ea.
>

What an excellent explanation. Thank you.

> Good luck!
> Sebastian.
>
> PS.  It looks like we do your homework here ;)

It .. is ... not! Because I am not a student!

This is my personal project, for hobby only :-)

Best,
Jun

> > Hello,
> >
> > I used dwarfdump to get information on source codes, and saw something
> > strange: one line of code may make up to 4 entries in debug_line?
> >
> > For example, please see the below code (from Linux kernel):
> >
> >
> > asmlinkage ssize_t sys_write(unsigned int fd, const char __user * buf,
> > size_t count)
> > {
> >     struct file *file;
> >     ssize_t ret = -EBADF;
> >     int fput_needed;
> >
> >     file = fget_light(fd, &fput_needed);
> >     if (file) {
> >         loff_t pos = file_pos_read(file);
> >         ret = vfs_write(file, buf, count, &pos);       <==== ? (line 369)
> >         file_pos_write(file, pos);
> >         fput_light(file, fput_needed);
> >     }
> >
> >     return ret;
> > }
> >
> >
> >
> > The line "ret = vfs_write(...)" at line 369 got 4 entries like below
> > (vfs_write() is a normal function, not a macro):
> >
> >
> > /home/jun/projects/linux-2.6.16.29/fs/read_write.c:       [369,-1]
> >    0xc01526c4      // new statement
> > /home/jun/projects/0928/linux-2.6.16.29/fs/read_write.c:
> > [369,-1]        0xc01526ca      // new statement
> > /home/jun/projects/0928/linux-2.6.16.29/fs/read_write.c:
> > [369,-1]        0xc01526d0      // new statement
> > /home/jun/projects/0928/linux-2.6.16.29/fs/read_write.c:
> > [369,-1]        0xc01526ea      // new statement
> >
> >
> > Is there any reason of that? As I observed, normally a line of code
> > has only 1 debug_line entry.
> >
> >
> > Many thanks.
> > Jun
> >
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> >
>
>