X-Git-Url: https://git.ralfj.de/web.git/blobdiff_plain/4fb0688c1bdca89c3e47307a0b3d82b63aaf8576..77f6f5e5733e33974a167477ae0528bb3f9d96b1:/ralf/_posts/2019-07-14-uninit.md

diff --git a/ralf/_posts/2019-07-14-uninit.md b/ralf/_posts/2019-07-14-uninit.md
index c6ee054..5aa60df 100644
--- a/ralf/_posts/2019-07-14-uninit.md
+++ b/ralf/_posts/2019-07-14-uninit.md
@@ -54,7 +54,7 @@ However, if you [run the example](https://play.rust-lang.org/?version=stable&mod
 ## What *is* uninitialized memory?
 
 How is this possible?
-The answer is that every byte in memory cannot just have a value in `0..256` (this is Rust/Ruby syntax for a left-inclusive right-exclusive range), it can also be "uninitialized".
+The answer is that, in the "abstract machine" that is used to specify the behavior of our program,  every byte in memory cannot just have a value in `0..256` (this is Rust/Ruby syntax for a left-inclusive right-exclusive range), it can also be "uninitialized".
 Memory *remembers* if you initialized it.
 The `x` that is passed to `always_return_true` is *not* the 8-bit representation of some number, it is an uninitialized byte.
 Performing operations such as comparison on uninitialized bytes is undefined behavior.
@@ -108,7 +108,7 @@ It runs on the Rust abstract machine, and that machine (which only exists in our
 The real, physical hardware that we end up running the compiled program on is a very efficient *but imprecise* implementation of this abstract machine, and all the rules that Rust has for undefined behavior work together to make sure that this imprecision is not visible for *well-behaved* (UB-free) programs.
 But for programs that do have UB, this "illusion" breaks down, and [anything is possible](https://raphlinus.github.io/programming/rust/2018/08/17/undefined-behavior.html).
 
-UB-free programs can be made sense of by looking at their assembly, but *whether* a program has UB is impossible to tell on that level.
+*Only* UB-free programs can be made sense of by looking at their assembly, but *whether* a program has UB is impossible to tell on that level.
 For that, you need to think in terms of the abstract machine.[^sanitizer]
 
 [^sanitizer]: This does imply that tools like valgrind, that work on the final assembly, can never reliably detect *all* UB.