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parser: Support unsafe(expr) (#5973)

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This commit is contained in:
Nick Treleaven
2020-07-28 09:20:52 +01:00
committed by GitHub
parent d7ed3cd8b7
commit 19c226fcf8
7 changed files with 54 additions and 39 deletions
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11
doc/docs.md
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@ -1907,10 +1907,10 @@ To mark potentially memory-unsafe operations, enclose them in an `unsafe` block:
```v
// allocate 2 uninitialized bytes & return a reference to them
mut p := unsafe { &byte(malloc(2)) }
mut p := unsafe(&byte(malloc(2)))
p[0] = `h` // Error: pointer indexing is only allowed in `unsafe` blocks
unsafe {
p[0] = `h`
p[0] = `h` // OK
p[1] = `i`
}
p++ // Error: pointer arithmetic is only allowed in `unsafe` blocks
@ -1920,13 +1920,12 @@ unsafe {
assert *p == `i`
```
Best practice is to avoid putting memory-safe expressions inside an `unsafe` block,
Best practice is to avoid putting memory-safe expressions inside an `unsafe` expression/block,
so that the reason for using `unsafe` is as clear as possible. Generally any code
you think is memory-safe should not be inside an `unsafe` block, so the compiler
can verify it.
you think is memory-safe should be verified by the compiler.
If you suspect your program does violate memory-safety, you have a head start on
finding the cause: look at the `unsafe` blocks (and how they interact with
finding the cause: look for the `unsafe` keyword (and how it affects the
surrounding code).
* Note: This is work in progress.