Subject:
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Re: Possible bug with bss allocation
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Sat, 22 Jul 2000 06:10:26 GMT
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Viewed:
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4126 times
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> I was having some random hangs with a legOS program. If I added a
> little code or subtracted a little, everything started working again.
> I've isolated it to a problem whereby writing a zero to the last byte of
> bss data will hang the RCX. This only happens when the length of the
> .text segment (and presumably .data and .bss segments) are just right.
> In my testing, I always had a multiple of 16 bytes of .bss data and no
> .data segment. If the .text segment's length mod 16 was equal to 4,
> then I got the hang. I'm guessing that some important housekeeping
> structure is overlapped with the end of the .bss segment and if the
> alignment is just write, then zeroing out that last byte of .bss data
> has dire consequences. This seemed to happen regardless to the
> magnitued of the .bss and .text sizes. The example below is pretty
> minimal, but I also saw it happening with a 4K text segment and 1K of
> bss. Here's a test program:
The common section is aligned to 16 bytes by ld. This is unknown to
the tools generating the final .lx files.
The fix is to force the alignment of the .bss section to 2, with this
ld will generate files that work with the current tools. I changed
genlds.c in CVS at sourceforge.net to output the correct linker script
for this.
If you are using this, please make shure genlds gets rebuild, issue a
make realclean in your legOS directory.
Eddie C. Dost
ecd@skynet.be
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Message is in Reply To:
 | | Possible bug with bss allocation
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| I was having some random hangs with a legOS program. If I added a little code or subtracted a little, everything started working again. I've isolated it to a problem whereby writing a zero to the last byte of bss data will hang the RCX. This only (...) (26 years ago, 22-Jul-00, to lugnet.robotics.rcx.legos)
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