1 //! Items which do not have a correspondence to any API in the proc_macro crate, 2 //! but are necessary to include in proc-macro2. 3 4 use crate::fallback; 5 use crate::imp; 6 use crate::marker::{ProcMacroAutoTraits, MARKER}; 7 use crate::Span; 8 use core::fmt::{self, Debug}; 9 10 /// Invalidate any `proc_macro2::Span` that exist on the current thread. 11 /// 12 /// The implementation of `Span` uses thread-local data structures and this 13 /// function clears them. Calling any method on a `Span` on the current thread 14 /// created prior to the invalidation will return incorrect values or crash. 15 /// 16 /// This function is useful for programs that process more than 2<sup>32</sup> 17 /// bytes of Rust source code on the same thread. Just like rustc, proc-macro2 18 /// uses 32-bit source locations, and these wrap around when the total source 19 /// code processed by the same thread exceeds 2<sup>32</sup> bytes (4 20 /// gigabytes). After a wraparound, `Span` methods such as `source_text()` can 21 /// return wrong data. 22 /// 23 /// # Example 24 /// 25 /// As of late 2023, there is 200 GB of Rust code published on crates.io. 26 /// Looking at just the newest version of every crate, it is 16 GB of code. So a 27 /// workload that involves parsing it all would overflow a 32-bit source 28 /// location unless spans are being invalidated. 29 /// 30 /// ``` 31 /// use flate2::read::GzDecoder; 32 /// use std::ffi::OsStr; 33 /// use std::io::{BufReader, Read}; 34 /// use std::str::FromStr; 35 /// use tar::Archive; 36 /// 37 /// rayon::scope(|s| { 38 /// for krate in every_version_of_every_crate() { 39 /// s.spawn(move |_| { 40 /// proc_macro2::extra::invalidate_current_thread_spans(); 41 /// 42 /// let reader = BufReader::new(krate); 43 /// let tar = GzDecoder::new(reader); 44 /// let mut archive = Archive::new(tar); 45 /// for entry in archive.entries().unwrap() { 46 /// let mut entry = entry.unwrap(); 47 /// let path = entry.path().unwrap(); 48 /// if path.extension() != Some(OsStr::new("rs")) { 49 /// continue; 50 /// } 51 /// let mut content = String::new(); 52 /// entry.read_to_string(&mut content).unwrap(); 53 /// match proc_macro2::TokenStream::from_str(&content) { 54 /// Ok(tokens) => {/* ... */}, 55 /// Err(_) => continue, 56 /// } 57 /// } 58 /// }); 59 /// } 60 /// }); 61 /// # 62 /// # fn every_version_of_every_crate() -> Vec<std::fs::File> { 63 /// # Vec::new() 64 /// # } 65 /// ``` 66 /// 67 /// # Panics 68 /// 69 /// This function is not applicable to and will panic if called from a 70 /// procedural macro. 71 #[cfg(span_locations)] 72 #[cfg_attr(docsrs, doc(cfg(feature = "span-locations")))] 73 pub fn invalidate_current_thread_spans() { 74 crate::imp::invalidate_current_thread_spans(); 75 } 76 77 /// An object that holds a [`Group`]'s `span_open()` and `span_close()` together 78 /// in a more compact representation than holding those 2 spans individually. 79 /// 80 /// [`Group`]: crate::Group 81 #[derive(Copy, Clone)] 82 pub struct DelimSpan { 83 inner: DelimSpanEnum, 84 _marker: ProcMacroAutoTraits, 85 } 86 87 #[derive(Copy, Clone)] 88 enum DelimSpanEnum { 89 #[cfg(wrap_proc_macro)] 90 Compiler { 91 join: proc_macro::Span, 92 open: proc_macro::Span, 93 close: proc_macro::Span, 94 }, 95 Fallback(fallback::Span), 96 } 97 98 impl DelimSpan { 99 pub(crate) fn new(group: &imp::Group) -> Self { 100 #[cfg(wrap_proc_macro)] 101 let inner = match group { 102 imp::Group::Compiler(group) => DelimSpanEnum::Compiler { 103 join: group.span(), 104 open: group.span_open(), 105 close: group.span_close(), 106 }, 107 imp::Group::Fallback(group) => DelimSpanEnum::Fallback(group.span()), 108 }; 109 110 #[cfg(not(wrap_proc_macro))] 111 let inner = DelimSpanEnum::Fallback(group.span()); 112 113 DelimSpan { 114 inner, 115 _marker: MARKER, 116 } 117 } 118 119 /// Returns a span covering the entire delimited group. 120 pub fn join(&self) -> Span { 121 match &self.inner { 122 #[cfg(wrap_proc_macro)] 123 DelimSpanEnum::Compiler { join, .. } => Span::_new(imp::Span::Compiler(*join)), 124 DelimSpanEnum::Fallback(span) => Span::_new_fallback(*span), 125 } 126 } 127 128 /// Returns a span for the opening punctuation of the group only. 129 pub fn open(&self) -> Span { 130 match &self.inner { 131 #[cfg(wrap_proc_macro)] 132 DelimSpanEnum::Compiler { open, .. } => Span::_new(imp::Span::Compiler(*open)), 133 DelimSpanEnum::Fallback(span) => Span::_new_fallback(span.first_byte()), 134 } 135 } 136 137 /// Returns a span for the closing punctuation of the group only. 138 pub fn close(&self) -> Span { 139 match &self.inner { 140 #[cfg(wrap_proc_macro)] 141 DelimSpanEnum::Compiler { close, .. } => Span::_new(imp::Span::Compiler(*close)), 142 DelimSpanEnum::Fallback(span) => Span::_new_fallback(span.last_byte()), 143 } 144 } 145 } 146 147 impl Debug for DelimSpan { 148 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { 149 Debug::fmt(&self.join(), f) 150 } 151 } 152