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

[Sebastian Krawczuk]

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.

Good luck!
Sebastian.

PS.  It looks like we do your homework here ;)

Jun Koi wrote:
> 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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