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Fix stacked borrows violation(s)

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With MIRIFLAGS=-Zmiri-track-raw-pointers, miri detects a violation of
stacked borrows because slice::get_unchecked produces a pointer which only has
provenance over the single element at that index, but
copy_nonoverlapping was used to copy that element and the one after it.
The new implementation uses .as_ptr() which returns a pointer that has
provenance over the whole buffer.
This commit is contained in:
Ben Kimock
2021-11-28 13:58:13 -05:00
parent c6e428a044
commit 8ea38413d2
2 changed files with 43 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/pretty/exponent.rs
+3 -3
View File
@@ -14,11 +14,11 @@ pub unsafe fn write_exponent3(mut k: isize, mut result: *mut u8) -> usize {
if k >= 100 {
*result = b'0' + (k / 100) as u8;
k %= 100;
let d = DIGIT_TABLE.get_unchecked(k as usize * 2);
let d = DIGIT_TABLE.as_ptr().offset(k * 2);
ptr::copy_nonoverlapping(d, result.offset(1), 2);
sign as usize + 3
} else if k >= 10 {
let d = DIGIT_TABLE.get_unchecked(k as usize * 2);
let d = DIGIT_TABLE.as_ptr().offset(k * 2);
ptr::copy_nonoverlapping(d, result, 2);
sign as usize + 2
} else {
@@ -38,7 +38,7 @@ pub unsafe fn write_exponent2(mut k: isize, mut result: *mut u8) -> usize {
debug_assert!(k < 100);
if k >= 10 {
let d = DIGIT_TABLE.get_unchecked(k as usize * 2);
let d = DIGIT_TABLE.as_ptr().offset(k * 2);
ptr::copy_nonoverlapping(d, result, 2);
sign as usize + 2
} else {
src/pretty/mantissa.rs
+40 -8
View File
@@ -15,10 +15,26 @@ pub unsafe fn write_mantissa_long(mut output: u64, mut result: *mut u8) {
let c1 = (c / 100) << 1;
let d0 = (d % 100) << 1;
let d1 = (d / 100) << 1;
ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c0 as usize), result.offset(-2), 2);
ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c1 as usize), result.offset(-4), 2);
ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(d0 as usize), result.offset(-6), 2);
ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(d1 as usize), result.offset(-8), 2);
ptr::copy_nonoverlapping(
DIGIT_TABLE.as_ptr().offset(c0 as isize),
result.offset(-2),
2,
);
ptr::copy_nonoverlapping(
DIGIT_TABLE.as_ptr().offset(c1 as isize),
result.offset(-4),
2,
);
ptr::copy_nonoverlapping(
DIGIT_TABLE.as_ptr().offset(d0 as isize),
result.offset(-6),
2,
);
ptr::copy_nonoverlapping(
DIGIT_TABLE.as_ptr().offset(d1 as isize),
result.offset(-8),
2,
);
result = result.offset(-8);
}
write_mantissa(output as u32, result);
@@ -31,19 +47,35 @@ pub unsafe fn write_mantissa(mut output: u32, mut result: *mut u8) {
output /= 10_000;
let c0 = (c % 100) << 1;
let c1 = (c / 100) << 1;
ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c0 as usize), result.offset(-2), 2);
ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c1 as usize), result.offset(-4), 2);
ptr::copy_nonoverlapping(
DIGIT_TABLE.as_ptr().offset(c0 as isize),
result.offset(-2),
2,
);
ptr::copy_nonoverlapping(
DIGIT_TABLE.as_ptr().offset(c1 as isize),
result.offset(-4),
2,
);
result = result.offset(-4);
}
if output >= 100 {
let c = ((output % 100) << 1) as u32;
output /= 100;
ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c as usize), result.offset(-2), 2);
ptr::copy_nonoverlapping(
DIGIT_TABLE.as_ptr().offset(c as isize),
result.offset(-2),
2,
);
result = result.offset(-2);
}
if output >= 10 {
let c = (output << 1) as u32;
ptr::copy_nonoverlapping(DIGIT_TABLE.get_unchecked(c as usize), result.offset(-2), 2);
ptr::copy_nonoverlapping(
DIGIT_TABLE.as_ptr().offset(c as isize),
result.offset(-2),
2,
);
} else {
*result.offset(-1) = b'0' + output as u8;
}