atomic-dbg
This crate provides dbg
, eprint
, and eprintln
, macros which work just like their counterparts in std, but which:
- Write atomically, up to the greatest length supported on the platform.
- Don't use locks (in userspace).
- Preserve libc's
errno
and Windows' last-error code value.
This means they can be used just about anywhere within a program, including inside allocator implementations, inside synchronization primitives, startup code, around FFI calls, inside signal handlers, and in the child process of a fork
before an exec
.
And, when multiple threads are printing, as long as their within the length supported on the platform, the output is readable instead of potentially interleaved with other output.
For example, this code:
use atomic_dbg::dbg;
fn main() {
dbg!(2, 3, 4);
}
Has this strace output:
write(2, "[examples/dbg.rs:4] 2 = 2\n[examples/dbg.rs:4] 3 = 3\n[examples/dbg.rs:4] 4 = 4\n", 78[examples/dbg.rs:4] 2 = 2
which is a single atomic write
call.
For comparison, with std::dbg
it looks like this:
write(2, "[", 1[) = 1
write(2, "examples/dbg.rs", 15examples/dbg.rs) = 15
write(2, ":", 1:) = 1
write(2, "4", 14) = 1
write(2, "] ", 2] ) = 2
write(2, "2", 12) = 1
write(2, " = ", 3 = ) = 3
write(2, "2", 12) = 1
write(2, "\n", 1
) = 1
write(2, "[", 1[) = 1
write(2, "examples/dbg.rs", 15examples/dbg.rs) = 15
write(2, ":", 1:) = 1
write(2, "4", 14) = 1
write(2, "] ", 2] ) = 2
write(2, "3", 13) = 1
write(2, " = ", 3 = ) = 3
write(2, "3", 13) = 1
write(2, "\n", 1
) = 1
write(2, "[", 1[) = 1
write(2, "examples/dbg.rs", 15examples/dbg.rs) = 15
write(2, ":", 1:) = 1
write(2, "4", 14) = 1
write(2, "] ", 2] ) = 2
write(2, "4", 14) = 1
write(2, " = ", 3 = ) = 3
write(2, "4", 14) = 1
write(2, "\n", 1
) = 1