tracing: Add support for span fields
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@ -68,7 +68,10 @@ typedef struct TracingSpanGuard TracingSpanGuard;
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/// Creates a span for a callsite.
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///
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/// The span must be freed when it goes out of scope.
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TracingSpanHandle* tracing_span_create(const TracingCallsite* callsite);
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TracingSpanHandle* tracing_span_create(
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const TracingCallsite* callsite,
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const char* const* field_values,
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size_t fields_len);
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/// Clones the given span.
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///
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@ -216,7 +219,7 @@ public:
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Span() : inner(nullptr, tracing_span_free) {}
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/// Use the `TracingSpan` macro instead of calling this constructor directly.
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Span(const TracingCallsite* callsite) : inner(tracing_span_create(callsite), tracing_span_free) {}
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Span(const TracingCallsite* callsite, const char* const* field_values, size_t fields_len) : inner(tracing_span_create(callsite, field_values, fields_len), tracing_span_free) {}
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Span(Span& span) : inner(std::move(span.inner)) {}
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Span(const Span& span) : inner(tracing_span_clone(span.inner.get()), tracing_span_free) {}
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@ -257,9 +260,31 @@ public:
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/// strings.
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#define TracingSpan(level, target, name) ([&] { \
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static constexpr const char* const FIELDS[] = {}; \
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const char* T_VALUES[] = {}; \
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static TracingCallsite* CALLSITE = \
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T_CALLSITE(name, target, level, FIELDS, true); \
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return tracing::Span(CALLSITE); \
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return tracing::Span( \
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CALLSITE, T_VALUES, T_ARRLEN(T_VALUES)); \
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}())
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/// Expands to a `tracing::Span` object which is used to record a span.
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/// The `Span::Enter` method on that object records that the span has been
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/// entered, and returns a RAII guard object, which will exit the span when
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/// dropped.
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///
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/// Arguments: (level, target, name, key, value[, key2, value2, ...])
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///
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/// level, target, name, and all keys MUST be static constants, and MUST be
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/// valid UTF-8 strings.
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#define TracingSpanFields(level, target, name, ...) ([&] { \
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static constexpr const char* const FIELDS[] = \
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{T_FIELD_NAMES(__VA_ARGS__)}; \
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const char* T_VALUES[] = \
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{T_FIELD_VALUES(__VA_ARGS__)}; \
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static TracingCallsite* CALLSITE = \
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T_CALLSITE(name, target, level, FIELDS, true); \
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return tracing::Span( \
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CALLSITE, T_VALUES, T_ARRLEN(T_VALUES)); \
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}())
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#endif
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@ -270,6 +270,9 @@ pub extern "C" fn tracing_callsite(
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}
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macro_rules! repeat {
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(0, $val:expr) => {
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[]
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};
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(1, $val:expr) => {
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[$val]
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};
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@ -435,14 +438,76 @@ macro_rules! repeat {
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}
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#[no_mangle]
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pub extern "C" fn tracing_span_create(callsite: *const FfiCallsite) -> *mut Span {
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pub extern "C" fn tracing_span_create(
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callsite: *const FfiCallsite,
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field_values: *const *const c_char,
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fields_len: usize,
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) -> *mut Span {
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let callsite = unsafe { &*callsite };
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let field_values = unsafe { slice::from_raw_parts(field_values, fields_len) };
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let meta = callsite.metadata();
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assert!(meta.is_span());
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let span = if level_enabled!(*meta.level()) && callsite.is_enabled() {
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Span::new(meta, &meta.fields().value_set(&[]))
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let mut fi = meta.fields().iter();
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let mut vi = field_values
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.iter()
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.map(|&p| unsafe { CStr::from_ptr(p) })
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.map(|cs| cs.to_string_lossy());
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macro_rules! new_span {
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($n:tt) => {
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Span::new(
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meta,
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&meta.fields().value_set(&repeat!(
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$n,
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(
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&fi.next().unwrap(),
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Some(&vi.next().unwrap().as_ref() as &dyn Value)
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)
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)),
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)
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};
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}
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// https://github.com/tokio-rs/tracing/issues/782 might help improve things here.
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match field_values.len() {
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0 => new_span!(0),
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1 => new_span!(1),
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2 => new_span!(2),
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3 => new_span!(3),
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4 => new_span!(4),
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5 => new_span!(5),
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6 => new_span!(6),
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7 => new_span!(7),
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8 => new_span!(8),
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9 => new_span!(9),
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10 => new_span!(10),
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11 => new_span!(11),
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12 => new_span!(12),
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13 => new_span!(13),
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14 => new_span!(14),
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15 => new_span!(15),
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16 => new_span!(16),
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17 => new_span!(17),
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18 => new_span!(18),
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19 => new_span!(19),
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20 => new_span!(20),
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21 => new_span!(21),
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22 => new_span!(22),
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23 => new_span!(23),
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24 => new_span!(24),
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25 => new_span!(25),
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26 => new_span!(26),
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27 => new_span!(27),
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28 => new_span!(28),
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29 => new_span!(29),
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30 => new_span!(30),
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31 => new_span!(31),
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32 => new_span!(32),
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_ => unimplemented!(),
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}
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} else {
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Span::none()
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};
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