Replies

John Regehrregehr@mastodon.social
Oct 1, 2026, 6:12 PM
reported now:
https://github.com/llvm/llvm-project/issues/228084
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mx alex tax1a - 2020 (6)atax1a@infosec.exchange
Oct 1, 2026, 2:21 AM
@regehr why not? sounds like a great place to put a stack!
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Slava Pestovslava@mathstodon.xyz
Oct 1, 2026, 2:22 AM
@atax1a @regehr it’s just preparing alignment for a very large allocation
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mx alex tax1a - 2020 (6)atax1a@infosec.exchange
Oct 1, 2026, 2:23 AM
@slava @regehr ah yes we love a good VLA
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John Regehrregehr@mastodon.social
Oct 1, 2026, 2:24 AM
@atax1a @slava it comes from a 1<<32 alligned alloca, this is totally legal in LLVM (if not obviously desirable) but it triggers an integer overflow in the 64-bit RISC-V backend
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David Chisnall (*Now with 50% more sarcasm!*)david_chisnall@infosec.exchange
Oct 1, 2026, 9:09 AM
@atax1a @regehr Ah, I see you’re familiar with AMD GPUs.
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David Chisnall (*Now with 50% more sarcasm!*)david_chisnall@infosec.exchange
Oct 1, 2026, 2:53 PM
@atax1a @regehr
For those missing context:
AMD GPUs place (placed?) their stack memory at address 0, which meant 0 was a valid memory address. This caused a bunch of problems in LLVM because LLVM assumes that a pointer at address 0 is invalid.
The C spec is more fun here. An integer constant expression of 0 is a null pointer but an implementation is free to determine that a constant expression that turns into some entirely different bit pattern when compiled. Some mainframes do this and null pointers are not represented as zero.
For CHERI C we aim to implement most of the 'de facto' C standard (i.e. all of the stuff that C programmers expect, even if the standard says they shouldn't). This includes being able to memset a struct with zero and have all of the pointer fields be filled with nulls.
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DougMerritt (log😅 = 💧log😄)dougmerritt@mathstodon.xyz
Oct 1, 2026, 2:23 AM
@regehr
Baby's first code generator :)
"It seemed like a good idea at the time!"
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Samlenary@types.pl
Oct 1, 2026, 2:45 AM
@regehr it's *so* aligned right now.
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Fabian Giesenrygorous@mastodon.gamedev.place
Oct 1, 2026, 4:05 AM
@regehr (affects thick Austrian accent) I need your clothes, your boots and your stack
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Per Vognsenpervognsen@mastodon.social
Oct 1, 2026, 4:06 AM
@rygorous @regehr Confession: as much as I work on compilers and related tools, every time I read or write the word 'terminator' I still get a mental image of The Terminator.
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Fabian Giesenrygorous@mastodon.gamedev.place
Oct 1, 2026, 4:07 AM
@pervognsen @regehr This is objectively correct.
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Florian 'floe' Echtlerfloe@hci.social
Oct 1, 2026, 5:19 AM
@rygorous @pervognsen @regehr
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Ron Garciarg9119@mathstodon.xyz
Oct 1, 2026, 10:54 PM
@regehr your github icon is sooo good!
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