Re: binary compatibity (mixing different gcc versions) in modules

[J Sloan <jjs@lexus.com>]

I always compile the nvidia tarball against
whatever kernel I'm running - it has been
quite stable thus used, and I've used it with
stock RH kernels, -ac kernels, -aa kernels
and 2.5 kernels...

Joe

Richard B. Johnson wrote:

>On 17 Jun 2002, Emmanuel Michon wrote:
>
>  
>
>>Hi,
>>
>>looking at nvidia proprietary driver, the makefile warns
>>the user against insmod'ing a module compiled with a gcc
>>version different from the one that was used to compile
>>the kernel.
>>
>>This sounds strange to me, since I never encountered this
>>problem.
>>
>>As a counterpart, what I'm sure of, is that you easily get system
>>crashes when insmod'ing a module resulting of the linking together 
>>(with ld -r) of object files (.o) that were not produced by the same gcc.
>>
>>Can someone give me a clue on what happens?
>>
>>    
>>
>
>Nothing happens if you don't use -fcaller-saves or some other such
>optimization(s). Even -fomit-frame-pointer is safe across called
>functions so there should not be a problem mixing and matching.
>
>Note that your 'C' runtime library was probably not created by your
>current C Compiler and your user-mode C programs probably run just
>fine.
>
>Very old GNU C compilers followed the "M$" convention of prepending
>an underscore on a global variable. Therefore "main:" became "_main:".
>With such a compiler output, the linker will have trouble.
>
>If you link together certain objects to make a module, you must
>ascertain that the objects were produced using the same kernel
>structures (read identical kernel version). As an example, the
>main module structure, used by the kernel to find out where your
>module's procedures are, is called: "struct file_operations".
>The first structure member used to be a pointer to lseek(), now
>it's an opaque object of type THIS_MODULE.
>
>Imagine the fun if you made a module with this mixup!
>
>Cheers,
>Dick Johnson
>
>Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
>
>                 Windows-2000/Professional isn't.
>
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