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Can't malloc the last 4KB of the heap #264

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opened 2021-03-17 14:10:08 -05:00 by MichaelBell · 5 comments

MichaelBell commented

2021-03-17 14:10:08 -05:00

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malloc won't allocate the last 4KB of available heap (addresses in 2003F000- 20040000). A simple test program is here: https://gist.github.com/MichaelBell/a13513a483a07a41c5b74e8458fba51d

I believe the problem is _sbrk should allow heap_end to be moved up to __StackLimit. I've got a commit which appears to fix the issue but I'm not sufficiently familiar with how this is meant to work to know whether that's the correct approach.

malloc won't allocate the last 4KB of available heap (addresses in 2003F000- 20040000). A simple test program is here: https://gist.github.com/MichaelBell/a13513a483a07a41c5b74e8458fba51d I believe the problem is _sbrk should allow heap_end to be moved up to __StackLimit. I've got a [commit which appears to fix the issue](https://github.com/MichaelBell/pico-sdk/commit/4d84592bef7cdeb2b1f4081ca528875c14fa447b) but I'm not sufficiently familiar with how this is meant to work to know whether that's the correct approach.

kilograham commented

2021-03-17 19:56:05 -05:00

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yes your fix looks sensible... it is all a bit of a hack (the OPTIMISTIC_SBRK thing) since SBRK is being called for 4K but you are not giving it 4K...

yes your fix looks sensible... it is all a bit of a hack (the OPTIMISTIC_SBRK thing) since SBRK is being called for 4K but you are not giving it 4K...

MichaelBell commented

2021-03-18 07:22:40 -05:00

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Cool, I've made a pull request with a brief explanation of what it does.

Cool, I've made a pull request with a brief explanation of what it does.

kilograham commented

2021-03-21 19:11:56 -05:00

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can you please rebase onto develop-1.1.1

can you please rebase onto develop-1.1.1

MichaelBell commented

2021-03-22 13:44:04 -05:00

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I've rebased and updated the PR.

I've rebased and updated the PR.

kilograham commented

2021-03-24 09:36:49 -05:00

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merged

merged

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