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Altera_Forum's avatar
Altera_Forum
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20 years ago

GCC

Dear gurus,

I have the following problem. I have built a library which is compiled and

linked separately from the rest of software. This library is stored in flash

memory as a standalone piece of software. Then I have built an application which

uses this library by calling its functions at some defined flash addresses. The

application has been compiled and linked separately from the library and it

resides at different addresses in flash.

Both the library and the application use global variables. These variables are

allocated at different ram addresses. Since GCC uses global pointer to reference

to global variables, when the application calls a library function, that function

is not able to reference its globals because the global pointer is assigned to the

application's ram area and not to library's ram area.

Can you suggest a way to workaround this problem ? (without suggesting to

rewrite the compiler ...)

Best Regards

/Alessandro

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    20 years ago

    Hi Alessandro,

    > Can you suggest a way to workaround this problem ?

    Disable use of the global pointer with the -G0 compiler option (for both library and app).

    If you _must_ use the gp, you can write some fixup code in your library to

    save/restore the gp. But, depending on your requirements ... it might not be

    worth the effort.

    Regards,

    --Scott
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    20 years ago

    --- Quote Start ---

    originally posted by alessandro@Feb 28 2006, 07:58 PM

    can you suggest a way to workaround this problem ? (without suggesting to

    rewrite the compiler ...)

    <div align='right'><{post_snapback}> (index.php?act=findpost&pid=12991)

    --- quote end ---

    --- Quote End ---

    Another possible workaround could be that the fixed locations of the functions you have to call in reality contains an assembler stub which only swaps the gp pointer value...

    bye

    PJ