Auto merge of #44312 - eddyb:static-by-any-other-name, r=alexcrichton

Use rvalue promotion to 'static instead of static items.

Fixes #44240. Among other things, in crates that do a lot of formatting, this could reduce the number of items, although I haven't measured the performance benefits. If there's a codegen slowdown, that should IMO be solved by caching the output of miri, *not* by using `static`.

r? @alexcrichton

2 files changed, 4 insertions, 16 deletions

diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index 7392a153e3b..7992aefcb42 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -545,7 +545,7 @@ impl fmt::Debug for CStr {
 #[stable(feature = "cstr_default", since = "1.10.0")]
 impl<'a> Default for &'a CStr {
     fn default() -> &'a CStr {
-        static SLICE: &'static [c_char] = &[0];
+        const SLICE: &'static [c_char] = &[0];
         unsafe { CStr::from_ptr(SLICE.as_ptr()) }
     }
 }
diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 72d561fae3b..8089671f309 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -66,23 +66,11 @@ macro_rules! panic {
         panic!("explicit panic")
     });
     ($msg:expr) => ({
-        $crate::rt::begin_panic($msg, {
-            // static requires less code at runtime, more constant data
-            static _FILE_LINE_COL: (&'static str, u32, u32) = (file!(), line!(),
-                __rust_unstable_column!());
-            &_FILE_LINE_COL
-        })
+        $crate::rt::begin_panic($msg, &(file!(), line!(), __rust_unstable_column!()))
     });
     ($fmt:expr, $($arg:tt)+) => ({
-        $crate::rt::begin_panic_fmt(&format_args!($fmt, $($arg)+), {
-            // The leading _'s are to avoid dead code warnings if this is
-            // used inside a dead function. Just `#[allow(dead_code)]` is
-            // insufficient, since the user may have
-            // `#[forbid(dead_code)]` and which cannot be overridden.
-            static _FILE_LINE_COL: (&'static str, u32, u32) = (file!(), line!(),
-                __rust_unstable_column!());
-            &_FILE_LINE_COL
-        })
+        $crate::rt::begin_panic_fmt(&format_args!($fmt, $($arg)+),
+                                    &(file!(), line!(), __rust_unstable_column!()))
     });
 }