Does MingW/Dev support #pragma data_seg

Beats me how the message body relates to the message subject, but you sound like you know what you are doing.

I'll answer the subject, since I do not understand the message (I suggest you post some code to explain).

The authors of GCC (of which MinGW is a Windows port) are pathalogically averse to #pragma directives. To do the same thing as #pragma data_seg you need to use a section attribute, the syntax for data is as follows:

<type/class> <identifier> __attribute__((section ("<segment_name>"), shared)) [= <initializer>] ;

e.g.
int foo __attribute__((section ("shared_seg"), shared)) = 0;

The 'shared' keyword is Windows NT specific (and presumably 2K and XP although the documentation does not state that). It allows the section to be shared among multiple executables/DLLs.

Section attribute can also be specified for functions, e.g:

extern void foobar (void) __attribute__ ((section ("bar")));

The documentation does not mention the 'shared' keyword in relation to functions, so I am not sure on that one, I guess you could try it, or maybe it does not matter?.

I've not ever done any of this BTW, I just know my way around the documentation!

Attributes do loads of stuff you'd otherwise use a pragma for.

References:
http://gcc.gnu.org/onlinedocs/gcc-3.2.3/gcc/Function-Attributes.html#Function%20Attributes
http://gcc.gnu.org/onlinedocs/gcc-3.2.3/gcc/Attribute-Syntax.html#Attribute%20Syntax
http://gcc.gnu.org/onlinedocs/gcc-3.2.3/gcc/Variable-Attributes.html#Variable%20Attributes
http://gcc.gnu.org/onlinedocs/gcc-3.2.3/gcc/Type-Attributes.html#Type%20Attributes
http://gcc.gnu.org/onlinedocs/gcc-3.2.3/gcc/C---Attributes.html#C++%20Attributes

There are some pragmas for som GCC variants, but not i386 versions:
http://gcc.gnu.org/onlinedocs/gcc-3.2.3/gcc/Pragmas.html#Pragmas

Clifford

Thanks, this was exactly what I was after. I just need to look for an alternative now to work on 9x series as well.

I'm assuming it's for a shared data segment, which I thought was possible on 9x. I could be very, very wrong though (as Clifford gave some very nice docs on)

What do you mean by "when the calling application is active?" I wonder if we can avoid shared anything with some clever thinking.

JMan

The documentation indicated that the shared keyword was for only nt based machines. When I implemented it to test it on a 9x series it compiled then produced and error at run time.

I don't think it is possible to avoid the shared segment as the system hook needs this capacity to be system wide rather than just attached to the application setting the hook. I have been attempting to work a mapped memory file as an alternative without any success todate.

If anyone can recommend a site that discusses mapped memory files in relation to creating an alternative form of shared segment for dll's I would appreciate it.

Here are two sites where you will find some information and source code about file mappings used as shared memory:

http://www.codeguru.com/system/index.shtml

http://www.codeproject.com/system

( codeproject is down for the moment)

Liviu

Thanks the sample code looks like it is exactly what I was after.

Thanks again