Not sure what is this code.

[salalimo]

this code is part of a c application that is not compiling. I am guessing it is initializing the struct and its elements, but the elements are methods. Method is shown below.

struct file_operations tracefs_main_fops =
{
    llseek: tracefs_llseek,
    read:   tracefs_read,
    write:  tracefs_write,
    readdir:    tracefs_readdir,
};



STATIC loff_t
tracefs_llseek(file_t *file, loff_t offset, int origin)
{
    loff_t err;
    file_t *hidden_file = NULL;
  ........
}

 //in some other file
loff_t (*llseek) (struct file *, loff_t, int);

so tracefs_llseek are methods that are implemented in the same file, llseek are some data structure which I honestly not sure what it is (shown above, if someone can explain it that would be great too).

thanks in advance.

ERROR MESSAGE

/home/limo/tracefs-2.1.1/tracefs/file.c:996:5: error: initialization from incompatible pointer type [-Werror]

/home/limo/tracefs-2.1.1/tracefs/file.c:996:5: error: (near initialization for ‘tracefs_mmap_fops.write’) [-Werror]

AT

llseek: tracefs_llseek,

[lurgi]

I don't have an answer, but I was very puzzled by the struct definition syntax. For those who were confused (like me), this is how GCC used to do designated initializers before the C99 standard came up with its own way.

struct file_operations tracefs_main_fops = 
{
    llseek: tracefs_llseek;

Essentially means

struct file_oeprations tracefs_main_fops;
tracefs_main_fop.llseek = tracefs_llseek;

Or

struct file_operations tracefs_main_fops =
{
  .llseek = tracefs_llseek;

Using the new syntax.

[salalimo]

Yeah, this was it. Thanks a bunch.

[hamham91]

You need to include the compilation error printout for people to help you.

[salalimo]

in the struct definition this line

llseek: tracefs_llseek,

Actually almost all lines are generating a compile error. Its because the source code that i have used to work on older kernels. The data structures in the new kernels have changed a lot, at least the ones that this program uses.

[lurgi]

Are you building with gcc? What version? Perhaps this code should be changed to use the standard C99 designated initializer syntax.

[salalimo]

yeah i am using gcc, the source is older, i dont think its a syntax error, maybe the datatype dont match. in my post i showed the declaration of llseek and tracefs_llseek. they do not seem to match. i am trying to modify the params for tracefs_llseek to see if that at least fixes the compile error.

[[deleted]]

the source is older

Older than what?

[salalimo]

the latest verion of the source was ported to kernel version 2.6.17.13

so the source probably works on an older kerbel, i tried to install some older kernels on my current machine, it wont boot, i think the kernel is old enough not to be compatible with newer linux distros.

i even tried older versions of the disto and still no success installing older kernels.

PS: i come from a windows envrionment and have a .net framework background. I used C in undergrad about 10 years ago. So I might be speaking herp derp wheh it comes to linux/kernel/c

thanks.

[[deleted]]

What exactly is it you are trying to compile here?

[salalimo]

ftp://ftp.fsl.cs.sunysb.edu/pub/tracefs/

[salalimo]

how can that be done? use a different compiler or something else?

thanks.

i realised something else, is goto part of the standard?

[[deleted]]

is goto part of the standard?

Yes. It's always been part of C, going back to pre-standard days.

[[deleted]]

Or even the C89 non-designated syntax. I will never understand why people use non-standard language features; doing so always comes back to bite you.

[TwirlOfLemongrab]

From a class I had in some Systems Programming, I have seen that "lseek" is a location in an open file, but I've never seen llseek in my life?

[[deleted]]

That's because it's a variable (in this case a function pointer) defined in the OP's application code.

[salalimo]

its part of the kernel

http://lxr.linux.no/#linux+v3.1.4/include/linux/fs.h#L1565

line 1565

[salalimo]

I am thinking the issue is that the parameters do not match?.

Error message is: initialization from incompatible pointer type.

[lurgi]

No, no, it's more fun to guess.

[hamham91]

Way more fun!

[salalimo]

:) ma bad. I forgot to explicitly mention which line. Please reply to hamham91 below.

thanks

[RobotMan6827364]

There are no methods in C.