Kunsheng

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Hello everyone,

I am dealing with some Linux kernel code, which define most its functions with Macros. The trouble I am having is to use those code in user space in Windows.

For example, I have a function defined like this:
-------------------------------------------------------------------------

#define list_for_each_entry_safe(pos, n, head, member) \
for (pos = list_entry((head)->next, typeid(*pos), member), \
n = list_entry(pos->member.next, typeid(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, typeid(*n), member))

-------------------------------------------------------------------------

And in user space code, I call it in this way:

--------------------------------------------------------

list_for_each_entry_safe( pcre_item, tmp,
&(((pcre_list_head_t *)(hr.value))->head), list)
{
// My code to handle each element in the list
}

----------------------------------------------------------


This is working like a charm in Linux, but I got errors in Windows:

It reminds me missing ';' after 'list_for_each_entry_safe( pcre_item, tmp,
&(((pcre_list_head_t *)(hr.value))->head), list)'.


Does this kind of linux code not working in Windows at all? (Linux is in GCC C stand and VC is ANSI C)

I prefer not to convert them to normal functions but keep it the way if it could be working under windows by some tricks.


Any idea?


Thanks,

-Kun

Sergei Steshenko

Does your code under Windows include a file where the needed macros are defined ?

Or do you the needed macro definitions copy-pasted into your code ?

osor

It seems you replaced the linux macro definition by substituting typeid for typeof. You cannot do this!

AFAIK (and my knowledge on VC) is quite limited, typeid != typeof. The typeid construct is part of the RTTI of ISO C++. The typeof construct is not ISO C or ISO C++, and it cannot be implemented portably on any given compiler. If you want to use it on windows, I suggest using mingwin-gcc or icc, as both of these are known to have a version of typeof compatible with that used in linux.

If your goal is to use this sort of code in userspace, I would simply recommend using C++ (and its template functionality will take care of this). You might instead try a hack that will create a macro for typeof by relying on other nonportable features of VC(++) as found here.

Kunsheng

Thanks, osor. I checked the site you refer to and it provides some #define functions similar to ones I got problem.

The biggest problem is that the following #define macros

-------------------------------------------------------------------------

#define list_for_each_entry_safe(pos, n, head, member) \
for (pos = list_entry((head)->next, typeid(*pos), member), \
n = list_entry(pos->member.next, typeid(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, typeid(*n), member))

-------------------------------------------------------------------------

is not working in my user space program in this way:

--------------------------------------------------------

list_for_each_entry_safe( pcre_item, tmp,
&(((pcre_list_head_t *)(hr.value))->head), list)
{
// My code to handle each element in the list
}

----------------------------------------------------------


looks like the '\' at the end of each lines is not compatible in VC, but the site you refer to is using this, weird, right ?

osor

I think you misunderstood. The problem is not the backslash, it is the fact that using typeid will give you undesired functionality (namely, instead of a compile-time string substitution for an object’s type, you will get an instance of the C++ class std::type_info.

My suggestion was the following: if this kind of feature is really that important to you, you should use standard ISO C++, which includes support for iterators and templates. You can use std::for_each or try out some of the more programmer-friendly options from boost. Rewrite your program to use this portable functionality.

If, however, you want to be hackish, you can create a header like the one linked above. Then, change typeid back to typeof (or to whatever identifier you chose for the macro in your header file) so that it all works out.

P.S.
It is unnecessary to repost unchanged code samples.

P.P.S
When posting future code, please enclose them with between [code] and [/code].

jf.argentino

Some remarks:

1°) GCC is a compiler collection, and you can choose which standard to use when compiling with the "-std=" option.

2°) Why? Kernel code is the kind of code where heavy use of macros could be interesting... But for "normal" programming it is not a good practice since it is really dangerous for many reasons. You'd better use function and if performance really matter you could forcing them as inlined.

3°) backslash is just an escape character, so the precompiler won't take in account the "newline" at the end of the line, which is necessary there since macro must stand in one line only.

By the way, if you're programming in C++, use containers like those in the STL, boost or any wide-spread portable libraries, this is true for C too, but I'm not aware of any containers library widely used, maybe glib from gtk+?