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tracing: fix macros "use of moved value" with log #1823

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merged 12 commits into from
Jan 29, 2022
Merged

tracing: fix macros "use of moved value" with log #1823

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874a462
tracing: fix macros "use of moved value" with log
Skepfyr Jan 9, 2022
bc81ef5
tracing: fix span macros with log feature
Skepfyr Jan 9, 2022
0ad95a9
tracing: revert fix span macros with log feature
Skepfyr Jan 11, 2022
68b56d0
tracing: Move LogValueSet into __macro_support
Skepfyr Jan 11, 2022
c20567a
tracing: Replace std with core in LogVisitor
Skepfyr Jan 11, 2022
50fd7f2
tracing: generate valueset only when needed
Skepfyr Jan 11, 2022
b4c6208
tracing: move some macro support behind log feature
Skepfyr Jan 17, 2022
ce02eda
tracing: add log_move_arg tests and fix log format
Skepfyr Jan 18, 2022
a691c5b
Merge branch 'master' into macros-with-log
hawkw Jan 19, 2022
a4e8d26
tracing: Add nop logger to global subcriber bench
Skepfyr Jan 23, 2022
0c1ab2b
Update tracing-core/src/field.rs
hawkw Jan 28, 2022
794040e
Merge branch 'master' into macros-with-log
hawkw Jan 29, 2022
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50 changes: 49 additions & 1 deletion tracing/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -980,7 +980,8 @@ pub mod __macro_support {
use crate::{collect::Interest, Metadata};
use core::fmt;
use core::sync::atomic::{AtomicUsize, Ordering};
use tracing_core::Once;
use tracing_core::field::{ValueSet, Visit};
use tracing_core::{Field, Once};

/// Callsite implementation used by macro-generated code.
///
Expand Down Expand Up @@ -1109,6 +1110,53 @@ pub mod __macro_support {
.finish()
}
}

/// Utility to format [`ValueSet`] for logging, used by macro-generated code.
///
/// /!\ WARNING: This is *not* a stable API! /!\
/// This type, and all code contained in the `__macro_support` module, is
/// a *private* API of `tracing`. It is exposed publicly because it is used
/// by the `tracing` macros, but it is not part of the stable versioned API.
/// Breaking changes to this module may occur in small-numbered versions
/// without warning.
#[derive(Debug)]
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pub struct LogValueSet<'a>(pub &'a ValueSet<'a>);
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i have a slight preference for giving this a new constructor, rather than a pub field, so that we can add new fields to it while still supporting earlier versions of the macros. however, i doubt this is an issue in practice, so it may not really matter...

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impl<'a> fmt::Display for LogValueSet<'a> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut visit = LogVisitor {
f,
is_first: true,
result: Ok(()),
};
self.0.record(&mut visit);
visit.result
}
}

struct LogVisitor<'a, 'b> {
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f: &'a mut fmt::Formatter<'b>,
is_first: bool,
result: fmt::Result,
}

impl Visit for LogVisitor<'_, '_> {
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fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
let res = if self.is_first {
self.is_first = false;
if field.name() == "message" {
write!(self.f, "{:?}", value)
} else {
write!(self.f, "{}={:?}", field.name(), value)
}
} else {
write!(self.f, " {}={:?}", field.name(), value)
};
Comment on lines +1154 to +1163
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nit, take it or leave it: this might look slightly nicer as a match?

Suggested change
let res = if self.is_first {
self.is_first = false;
if field.name() == "message" {
write!(self.f, "{:?}", value)
} else {
write!(self.f, "{}={:?}", field.name(), value)
}
} else {
write!(self.f, " {}={:?}", field.name(), value)
};
let res = match field.name() {
"message" if self.is_first() => write!(self.f, "{:?}", value),
"message" => write!(self.f, " {:?}", value),
name if self.is_first => write!(self.f, "{}={:?}", name, value),
name => write!(self.f, " {}={:?}", name, value,
};
self.is_first = false;

though, up to you

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I prefer the explicit something is only weird about the first one of the if. However, your snippet does produce a different output to mine, in the case of message not being the first field. Mine would produce:

foo=bar message=Hi! baz=quux

whereas yours would produce:

foo=bar Hi! baz=quux

Is that behaviour ok, or should I change it to be in line with yours?

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in practice, the valueset! macro will always re-order the message field to come first, so it doesn't really matter whether we handle it differently if it isn't the first field. i don't have a strong opinion about this code, so it's fine to leave it the way you had it if you prefer.

if let Err(err) = res {
self.result = self.result.and(Err(err));
}
}
}
}

mod sealed {
Expand Down
183 changes: 83 additions & 100 deletions tracing/src/macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -32,22 +32,24 @@ macro_rules! span {
fields: $($fields)*
};
let mut interest = $crate::collect::Interest::never();
(|value_set| {
if $crate::level_enabled!($lvl)
&& { interest = CALLSITE.interest(); !interest.is_never() }
&& CALLSITE.is_enabled(interest)
{
let meta = CALLSITE.metadata();
// span with explicit parent
$crate::Span::child_of($parent, meta, &value_set)
} else {
let span = CALLSITE.disabled_span();
$crate::if_log_enabled! { $lvl, {
span.record_all(&value_set);
}};
span
}
})($crate::valueset!(CALLSITE.metadata().fields(), $($fields)*))
if $crate::level_enabled!($lvl)
&& { interest = CALLSITE.interest(); !interest.is_never() }
&& CALLSITE.is_enabled(interest)
{
let meta = CALLSITE.metadata();
// span with explicit parent
$crate::Span::child_of(
$parent,
meta,
&$crate::valueset!(meta.fields(), $($fields)*),
)
} else {
let span = CALLSITE.disabled_span();
$crate::if_log_enabled! { $lvl, {
span.record_all(&$crate::valueset!(CALLSITE.metadata().fields(), $($fields)*));
}};
span
}
}
};
(target: $target:expr, $lvl:expr, $name:expr, $($fields:tt)*) => {
Expand All @@ -62,22 +64,23 @@ macro_rules! span {
};

let mut interest = $crate::collect::Interest::never();
(|value_set| {
if $crate::level_enabled!($lvl)
&& { interest = CALLSITE.interest(); !interest.is_never() }
&& CALLSITE.is_enabled(interest)
{
let meta = CALLSITE.metadata();
// span with contextual parent
$crate::Span::new(meta, &value_set)
} else {
let span = CALLSITE.disabled_span();
$crate::if_log_enabled! { $lvl, {
span.record_all(&value_set);
}};
span
}
})($crate::valueset!(CALLSITE.metadata().fields(), $($fields)*))
if $crate::level_enabled!($lvl)
&& { interest = CALLSITE.interest(); !interest.is_never() }
&& CALLSITE.is_enabled(interest)
{
let meta = CALLSITE.metadata();
// span with contextual parent
$crate::Span::new(
meta,
&$crate::valueset!(meta.fields(), $($fields)*),
)
} else {
let span = CALLSITE.disabled_span();
$crate::if_log_enabled! { $lvl, {
span.record_all(&$crate::valueset!(CALLSITE.metadata().fields(), $($fields)*));
}};
span
}
}
};
(target: $target:expr, parent: $parent:expr, $lvl:expr, $name:expr) => {
Expand Down Expand Up @@ -594,25 +597,33 @@ macro_rules! event {
level: $lvl,
fields: $($fields)*
};
(|value_set: $crate::field::ValueSet| {

let enabled = $crate::level_enabled!($lvl) && {
let interest = CALLSITE.interest();
!interest.is_never() && CALLSITE.is_enabled(interest)
};
if enabled {
(|value_set: $crate::field::ValueSet| {
$crate::__tracing_log!(
target: $target,
$lvl,
&value_set
);
let meta = CALLSITE.metadata();
// event with explicit parent
$crate::Event::child_of(
$parent,
meta,
&value_set
);
})($crate::valueset!(CALLSITE.metadata().fields(), $($fields)*));
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is there a reason we still need the closure in the event! macros, but we don't in the span! macros? I haven't actually tried it yet, but it seems like we should be able to just write this and get exactly the same behavior:

Suggested change
(|value_set: $crate::field::ValueSet| {
$crate::__tracing_log!(
target: $target,
$lvl,
&value_set
);
let meta = CALLSITE.metadata();
// event with explicit parent
$crate::Event::child_of(
$parent,
meta,
&value_set
);
})($crate::valueset!(CALLSITE.metadata().fields(), $($fields)*));
let value_set = ($crate::valueset!(CALLSITE.metadata().fields(), $($fields)*);
$crate::__tracing_log!(
target: $target,
$lvl,
&value_set
);
let meta = CALLSITE.metadata();
// event with explicit parent
$crate::Event::child_of(
$parent,
meta,
&value_set
);

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This doesn't work for the reasons mentioned elsewhere, however I can replace the closures with function calls which may be preferable (it also appears to improve perf, see benchmarking comment). However, those functions do look a bit weird:

#[inline]
pub fn log_and_dispatcht(target: &str, callsite: &MacroCallsite, value_set: ValueSet) {
        let meta = callsite.metadata();
        // event with contextual parent
        $crate::Event::dispatch(
            meta,
            &value_set
        );
        $crate::__tracing_log!(
            target: target,
            $lvl,
            &value_set
        );
}

and similarly a log_and_event, I imagine both would go in the __macro_support module.

} else {
$crate::__tracing_log!(
target: $target,
$lvl,
value_set
&$crate::valueset!(CALLSITE.metadata().fields(), $($fields)*)
);
if $crate::level_enabled!($lvl) {
let interest = CALLSITE.interest();
if !interest.is_never() && CALLSITE.is_enabled(interest) {
let meta = CALLSITE.metadata();
// event with explicit parent
$crate::Event::child_of(
$parent,
meta,
&value_set
);
}
}
})($crate::valueset!(CALLSITE.metadata().fields(), $($fields)*));
}
});

(target: $target:expr, parent: $parent:expr, $lvl:expr, { $($fields:tt)* }, $($arg:tt)+ ) => (
Expand Down Expand Up @@ -643,25 +654,31 @@ macro_rules! event {
level: $lvl,
fields: $($fields)*
};
(|value_set: $crate::field::ValueSet| {
let enabled = $crate::level_enabled!($lvl) && {
let interest = CALLSITE.interest();
!interest.is_never() && CALLSITE.is_enabled(interest)
};
if enabled {
(|value_set: $crate::field::ValueSet| {
let meta = CALLSITE.metadata();
// event with contextual parent
$crate::Event::dispatch(
meta,
&value_set
);
$crate::__tracing_log!(
target: $target,
$lvl,
&value_set
);
})($crate::valueset!(CALLSITE.metadata().fields(), $($fields)*));
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similarly, it seems like the closure should be able to be replaced by a let-binding?

} else {
$crate::__tracing_log!(
target: $target,
$lvl,
value_set
&$crate::valueset!(CALLSITE.metadata().fields(), $($fields)*)
);
if $crate::level_enabled!($lvl) {
let interest = CALLSITE.interest();
if !interest.is_never() && CALLSITE.is_enabled(interest) {
let meta = CALLSITE.metadata();
//let value_set = $crate::valueset!(meta.fields(), $($fields)*);
// event with contextual parent
$crate::Event::dispatch(
meta,
&value_set
);
}
}
})($crate::valueset!(CALLSITE.metadata().fields(), $($fields)*));
}
});
(target: $target:expr, $lvl:expr, { $($fields:tt)* }, $($arg:tt)+ ) => (
$crate::event!(
Expand Down Expand Up @@ -2160,50 +2177,16 @@ macro_rules! __tracing_stringify {
#[doc(hidden)]
#[macro_export]
macro_rules! __tracing_log {
(target: $target:expr, $level:expr, $($field:tt)+ ) => {};
(target: $target:expr, $level:expr, $value_set:expr ) => {};
}

#[cfg(feature = "log")]
#[doc(hidden)]
#[macro_export]
macro_rules! __tracing_log {
(target: $target:expr, $level:expr, $value_set:ident ) => {
(target: $target:expr, $level:expr, $value_set:expr ) => {
$crate::if_log_enabled! { $level, {
use $crate::{log, field};
struct LogValueSet<'a>(&'a field::ValueSet<'a>);
impl<'a> std::fmt::Display for LogValueSet<'a> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
let mut visit = Visit {
f,
is_first: true,
result: Ok(()),
};
self.0.record(&mut visit);
visit.result
}
}
struct Visit<'a, 'b> {
f: &'a mut std::fmt::Formatter<'b>,
is_first: bool,
result: std::fmt::Result,
}
impl field::Visit for Visit<'_, '_> {
fn record_debug(&mut self, field: &field::Field, value: &dyn std::fmt::Debug) {
let res = if self.is_first {
self.is_first = false;
if field.name() == "message" {
write!(self.f, "{:?}", value)
} else {
write!(self.f, "{}={:?}", field.name(), value)
}
} else {
write!(self.f, " {}={:?}", field.name(), value)
};
if let Err(err) = res {
self.result = self.result.and(Err(err));
}
}
}
use $crate::log;
let level = $crate::level_to_log!($level);
if level <= log::max_level() {
let log_meta = log::Metadata::builder()
Expand All @@ -2217,7 +2200,7 @@ macro_rules! __tracing_log {
.module_path(Some(module_path!()))
.line(Some(line!()))
.metadata(log_meta)
.args(format_args!("{}", LogValueSet(&$value_set)))
.args(format_args!("{}", $crate::__macro_support::LogValueSet($value_set)))
.build());
}
}
Expand Down