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STM8 Readme: Add page0 null pointer check notes.

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Kelvin Lawson
2010-02-17 00:49:29 +00:00
parent c00ce7c1ec
commit 9205a742ee
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ports/stm8/README
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@@ -347,6 +347,17 @@ your calculations.
As mentioned previously, this RAM layout is only the one utilised by the
test applications. You may choose whatever layout you like.
Note that on this platform data can be placed at address 0x0, but the
Atomthreads kernel performs validity checks on pointers to ensure they
are not NULL pointers (point to address 0x0). For this reason the
example projects (STVD and Makefile) force the linker to not use address
0x0 and instead start the page0 space at 0x2. This ensures that the
linker does not place any data at address 0x0, and hence all NULL-ptr
checks are still suitable checks for valid pointers. This does, however,
waste 2 bytes. For your own projects you can force this within STVD by
editing the project linker settings (Input -> Zero Page start at 0x2)
or by editing the linker .LKF file as can be seen in atomthreads.lkf.
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