From a72767970adbe3600d1b66eff118ba4dd732c804 Mon Sep 17 00:00:00 2001 From: "Panashe M. Fundira" Date: Wed, 27 Jul 2016 13:12:35 -0400 Subject: [PATCH] Update docs for assert! and debug_assert! --- src/libcore/macros.rs | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs index 43868d124a22..e3207a0a86c4 100644 --- a/src/libcore/macros.rs +++ b/src/libcore/macros.rs @@ -32,8 +32,19 @@ macro_rules! panic { /// Ensure that a boolean expression is `true` at runtime. /// -/// This will invoke the `panic!` macro if the provided expression cannot be -/// evaluated to `true` at runtime. +/// This will ensure the termination of the program if the provided expression +/// cannot be evaluated to `true` at runtime by means of an unrecoverable error +/// (not necessarily a `panic!`, can also be an `abort`). +/// +/// Assertions are always checked in both debug and release builds, and cannot +/// be disabled. +/// +/// Unsafe code relies on `assert!` to enforce run-time invariants that, if +/// violated could lead to unsafety. +/// +/// Other use-cases of `assert!` include +/// [testing](https://doc.rust-lang.org/book/testing.html) and enforcing +/// run-time invariants in safe code (whose violation cannot result in unsafety). /// /// This macro has a second version, where a custom panic message can be provided. /// @@ -123,6 +134,13 @@ macro_rules! assert_eq { /// expensive to be present in a release build but may be helpful during /// development. /// +/// An unchecked assertion allows a program in an inconsistent state to keep +/// running, which might have unexpected consequences but does not introduce +/// unsafety as long as this only happens in safe code. The performance cost +/// of assertions, is however, not measurable in general. Replacing `assert!` +/// with `debug_assert!` is thus only encourage after thorough profiling, and +/// more importantly, only in safe code! +/// /// # Examples /// /// ```