Rollup merge of #22980 - alexcrichton:debug-assertions, r=pnkfelix

 This commit is an implementation of [RFC 563][rfc] which adds a new
`cfg(debug_assertions)` directive which is specially recognized and calculated
by the compiler. The flag is turned off at any optimization level greater than 1
and may also be explicitly controlled through the `-C debug-assertions`
flag.

[rfc]: https://github.com/rust-lang/rfcs/pull/563

The `debug_assert!` and `debug_assert_eq!` macros now respect this instead of
the `ndebug` variable and `ndebug` no longer holds any meaning to the standard
library.

Code which was previously relying on `not(ndebug)` to gate expensive code should
be updated to rely on `debug_assertions` instead.

Closes #22492
[breaking-change]

8 files changed, 69 insertions, 2 deletions

diff --git a/src/test/run-fail/overflowing-add.rs b/src/test/run-fail/overflowing-add.rs
index 34a03e5f008..cd13b817c2b 100644
--- a/src/test/run-fail/overflowing-add.rs
+++ b/src/test/run-fail/overflowing-add.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // error-pattern:thread '<main>' panicked at 'arithmetic operation overflowed'
+// compile-flags: -C debug-assertions
 
 // (Work around constant-evaluation)
 fn value() -> u8 { 200 }
diff --git a/src/test/run-fail/overflowing-mul.rs b/src/test/run-fail/overflowing-mul.rs
index b18d99cd232..5d2f5396240 100644
--- a/src/test/run-fail/overflowing-mul.rs
+++ b/src/test/run-fail/overflowing-mul.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // error-pattern:thread '<main>' panicked at 'arithmetic operation overflowed'
+// compile-flags: -C debug-assertions
 
 // (Work around constant-evaluation)
 fn value() -> u8 { 200 }
diff --git a/src/test/run-fail/overflowing-sub.rs b/src/test/run-fail/overflowing-sub.rs
index ee32291eca6..b089dccbaa5 100644
--- a/src/test/run-fail/overflowing-sub.rs
+++ b/src/test/run-fail/overflowing-sub.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // error-pattern:thread '<main>' panicked at 'arithmetic operation overflowed'
+// compile-flags: -C debug-assertions
 
 // (Work around constant-evaluation)
 fn value() -> u8 { 42 }
diff --git a/src/test/run-make/debug-assertions/Makefile b/src/test/run-make/debug-assertions/Makefile
new file mode 100644
index 00000000000..71297562768
--- /dev/null
+++ b/src/test/run-make/debug-assertions/Makefile
@@ -0,0 +1,21 @@
+-include ../tools.mk
+
+all:
+	$(RUSTC) debug.rs -C debug-assertions=no
+	$(call RUN,debug) good
+	$(RUSTC) debug.rs -C opt-level=0
+	$(call RUN,debug) bad
+	$(RUSTC) debug.rs -C opt-level=1
+	$(call RUN,debug) good
+	$(RUSTC) debug.rs -C opt-level=2
+	$(call RUN,debug) good
+	$(RUSTC) debug.rs -C opt-level=3
+	$(call RUN,debug) good
+	$(RUSTC) debug.rs -O
+	$(call RUN,debug) good
+	$(RUSTC) debug.rs
+	$(call RUN,debug) bad
+	$(RUSTC) debug.rs -C debug-assertions=yes -O
+	$(call RUN,debug) bad
+	$(RUSTC) debug.rs -C debug-assertions=yes -C opt-level=1
+	$(call RUN,debug) bad
diff --git a/src/test/run-make/debug-assertions/debug.rs b/src/test/run-make/debug-assertions/debug.rs
new file mode 100644
index 00000000000..a0ccc75afd0
--- /dev/null
+++ b/src/test/run-make/debug-assertions/debug.rs
@@ -0,0 +1,42 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![deny(warnings)]
+
+use std::env;
+use std::thread;
+
+fn main() {
+    let should_fail = env::args().nth(1) == Some("bad".to_string());
+
+    assert_eq!(thread::spawn(debug_assert_eq).join().is_err(), should_fail);
+    assert_eq!(thread::spawn(debug_assert).join().is_err(), should_fail);
+    assert_eq!(thread::spawn(overflow).join().is_err(), should_fail);
+}
+
+fn debug_assert_eq() {
+    let mut hit1 = false;
+    let mut hit2 = false;
+    debug_assert_eq!({ hit1 = true; 1 }, { hit2 = true; 2 });
+    assert!(!hit1);
+    assert!(!hit2);
+}
+
+fn debug_assert() {
+    let mut hit = false;
+    debug_assert!({ hit = true; false });
+    assert!(!hit);
+}
+
+fn overflow() {
+    fn add(a: u8, b: u8) -> u8 { a + b }
+
+    add(200u8, 200u8);
+}
diff --git a/src/test/run-pass/conditional-debug-macro-off.rs b/src/test/run-pass/conditional-debug-macro-off.rs
index b5a5f57d07a..90142350772 100644
--- a/src/test/run-pass/conditional-debug-macro-off.rs
+++ b/src/test/run-pass/conditional-debug-macro-off.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags: --cfg ndebug
+// compile-flags: -C debug-assertions=no
 // exec-env:RUST_LOG=conditional-debug-macro-off=4
 
 #[macro_use]
diff --git a/src/test/run-pass/logging-enabled-debug.rs b/src/test/run-pass/logging-enabled-debug.rs
index 262d9b21eb4..dfc92728270 100644
--- a/src/test/run-pass/logging-enabled-debug.rs
+++ b/src/test/run-pass/logging-enabled-debug.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-flags:--cfg ndebug
+// compile-flags:-C debug-assertions=no
 // exec-env:RUST_LOG=logging-enabled-debug=debug
 
 #[macro_use]
diff --git a/src/test/run-pass/logging-separate-lines.rs b/src/test/run-pass/logging-separate-lines.rs
index 8526dfe72da..82a155b1173 100644
--- a/src/test/run-pass/logging-separate-lines.rs
+++ b/src/test/run-pass/logging-separate-lines.rs
@@ -10,6 +10,7 @@
 
 // ignore-windows
 // exec-env:RUST_LOG=debug
+// compile-flags:-C debug-assertions=y
 
 #[macro_use]
 extern crate log;