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adjust documentation and tests for hash in light of into iterator for… #1

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cedric-h
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@cedric-h cedric-h commented Dec 7, 2019

… arrays

I checked each location where .iter().cloned() was used.
There were some places where it was genuinely the right choice, because the list that the HashSet/Map was being made from was used again afterwards.
In other places, the list wasn't used again, so I figured it was safe to use .into_iter() in place of .iter().cloned(), avoiding copying memory for no reason.

A simple grep for .iter().cloned() reveals that there are a lot more places where this would need to be fixed; I chose to start with HashMap/Set because they were simply the most salient in my eyes.

@cedric-h
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cedric-h commented Dec 7, 2019

Some relevant PRs/Issues:
rust-lang#65819
rust-lang#66145

@LukasKalbertodt
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@cedric-h Sorry for my late reply and thanks a bunch! Your PR will help a lot. However, I'd like to wait with merging this until we decided how to proceed with my main PR. I hope you don't mind!

@cedric-h
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All good!

@LukasKalbertodt
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Since I needed to rebase and adjust tons of other places, I now simply replaced all of those iter().cloned() occurrences (and more) myself instead of cherry picking your commit. But thanks a ton anyway!

LukasKalbertodt pushed a commit that referenced this pull request Feb 14, 2021
HWAddressSanitizer support

#  Motivation
Compared to regular ASan, HWASan has a [smaller overhead](https://source.android.com/devices/tech/debug/hwasan). The difference in practice is that HWASan'ed code is more usable, e.g. Android device compiled with HWASan can be used as a daily driver.

# Example
```
fn main() {
    let xs = vec![0, 1, 2, 3];
    let _y = unsafe { *xs.as_ptr().offset(4) };
}
```
```
==223==ERROR: HWAddressSanitizer: tag-mismatch on address 0xefdeffff0050 at pc 0xaaaad00b3468
READ of size 4 at 0xefdeffff0050 tags: e5/00 (ptr/mem) in thread T0
    #0 0xaaaad00b3464  (/root/main+0x53464)
    #1 0xaaaad00b39b4  (/root/main+0x539b4)
    rust-lang#2 0xaaaad00b3dd0  (/root/main+0x53dd0)
    rust-lang#3 0xaaaad00b61dc  (/root/main+0x561dc)
    rust-lang#4 0xaaaad00c0574  (/root/main+0x60574)
    rust-lang#5 0xaaaad00b6290  (/root/main+0x56290)
    rust-lang#6 0xaaaad00b6170  (/root/main+0x56170)
    rust-lang#7 0xaaaad00b3578  (/root/main+0x53578)
    rust-lang#8 0xffff81345e70  (/lib64/libc.so.6+0x20e70)
    rust-lang#9 0xaaaad0096310  (/root/main+0x36310)

[0xefdeffff0040,0xefdeffff0060) is a small allocated heap chunk; size: 32 offset: 16
0xefdeffff0050 is located 0 bytes to the right of 16-byte region [0xefdeffff0040,0xefdeffff0050)
allocated here:
    #0 0xaaaad009bcdc  (/root/main+0x3bcdc)
    #1 0xaaaad00b1eb0  (/root/main+0x51eb0)
    rust-lang#2 0xaaaad00b20d4  (/root/main+0x520d4)
    rust-lang#3 0xaaaad00b2800  (/root/main+0x52800)
    rust-lang#4 0xaaaad00b1cf4  (/root/main+0x51cf4)
    rust-lang#5 0xaaaad00b33d4  (/root/main+0x533d4)
    rust-lang#6 0xaaaad00b39b4  (/root/main+0x539b4)
    rust-lang#7 0xaaaad00b61dc  (/root/main+0x561dc)
    rust-lang#8 0xaaaad00b3578  (/root/main+0x53578)
    rust-lang#9 0xaaaad0096310  (/root/main+0x36310)

Thread: T0 0xeffe00002000 stack: [0xffffc0590000,0xffffc0d90000) sz: 8388608 tls: [0xffff81521020,0xffff815217d0)
Memory tags around the buggy address (one tag corresponds to 16 bytes):
  0xfefcefffef80: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffef90: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefa0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefb0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefc0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefd0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffefe0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefcefffeff0: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
=>0xfefceffff000: a2  a2  05  00  e5 [00] 00  00  00  00  00  00  00  00  00  00
  0xfefceffff010: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff020: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff030: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff040: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff050: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff060: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff070: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
  0xfefceffff080: 00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
Tags for short granules around the buggy address (one tag corresponds to 16 bytes):
  0xfefcefffeff0: ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..
=>0xfefceffff000: ..  ..  c5  ..  .. [..] ..  ..  ..  ..  ..  ..  ..  ..  ..  ..
  0xfefceffff010: ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..  ..
See https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html#short-granules for a description of short granule tags
Registers where the failure occurred (pc 0xaaaad00b3468):
    x0  e500efdeffff0050  x1  0000000000000004  x2  0000ffffc0d8f5a0  x3  0200efff00000000
    x4  0000ffffc0d8f4c0  x5  000000000000004f  x6  00000ffffc0d8f36  x7  0000efff00000000
    x8  e500efdeffff0050  x9  0200efff00000000  x10 0000000000000000  x11 0200efff00000000
    x12 0200effe000006b0  x13 0200effe000006b0  x14 0000000000000008  x15 00000000c00000cf
    x16 0000aaaad00a0afc  x17 0000000000000003  x18 0000000000000001  x19 0000ffffc0d8f718
    x20 ba00ffffc0d8f7a0  x21 0000aaaad00962e0  x22 0000000000000000  x23 0000000000000000
    x24 0000000000000000  x25 0000000000000000  x26 0000000000000000  x27 0000000000000000
    x28 0000000000000000  x29 0000ffffc0d8f650  x30 0000aaaad00b3468
```

# Comments/Caveats
* HWASan is only supported on arm64.
* I'm not sure if I should add a feature gate or piggyback on the existing one for sanitizers.
* HWASan requires `-C target-feature=+tagged-globals`. That flag should probably be set transparently to the user. Not sure how to go about that.

# TODO
* Need more tests.
* Update documentation.
* Fix symbolization.
* Integrate with CI
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