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Rollup merge of rust-lang#119033 - Zalathar:unicode, r=davidtwco
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coverage: `llvm-cov` expects column numbers to be bytes, not code points

Normally the compiler emits column numbers as a 1-based number of Unicode code points.

But when we embed coverage mappings for `-Cinstrument-coverage`, those mappings will ultimately be read by the `llvm-cov` tool. That tool assumes that column numbers are 1-based numbers of *bytes*, and relies on that assumption when slicing up source code to apply highlighting (in HTML reports, and in text-based reports with colour).

For the very common case of all-ASCII source code, bytes and code points are the same, so the difference isn't noticeable. But for code that contains non-ASCII characters, emitting column numbers as code points will result in `llvm-cov` slicing strings in the wrong places, producing mangled output or fatal errors.

(See taiki-e/cargo-llvm-cov#275 as an example of what can go wrong.)
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matthiaskrgr authored Jan 8, 2024
2 parents d8b03c0 + 6971e93 commit 32089a9
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90 changes: 70 additions & 20 deletions compiler/rustc_mir_transform/src/coverage/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ use rustc_middle::mir::{
use rustc_middle::ty::TyCtxt;
use rustc_span::def_id::LocalDefId;
use rustc_span::source_map::SourceMap;
use rustc_span::{Span, Symbol};
use rustc_span::{BytePos, Pos, RelativeBytePos, Span, Symbol};

/// Inserts `StatementKind::Coverage` statements that either instrument the binary with injected
/// counters, via intrinsic `llvm.instrprof.increment`, and/or inject metadata used during codegen
Expand Down Expand Up @@ -107,6 +107,12 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
);

let mappings = self.create_mappings(&coverage_spans, &coverage_counters);
if mappings.is_empty() {
// No spans could be converted into valid mappings, so skip this function.
debug!("no spans could be converted into valid mappings; skipping");
return;
}

self.inject_coverage_statements(bcb_has_coverage_spans, &coverage_counters);

self.mir_body.function_coverage_info = Some(Box::new(FunctionCoverageInfo {
Expand Down Expand Up @@ -148,9 +154,9 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> {
// Flatten the spans into individual term/span pairs.
.flat_map(|(term, spans)| spans.iter().map(move |&span| (term, span)))
// Convert each span to a code region, and create the final mapping.
.map(|(term, span)| {
let code_region = make_code_region(source_map, file_name, span, body_span);
Mapping { term, code_region }
.filter_map(|(term, span)| {
let code_region = make_code_region(source_map, file_name, span, body_span)?;
Some(Mapping { term, code_region })
})
.collect::<Vec<_>>()
}
Expand Down Expand Up @@ -252,41 +258,85 @@ fn inject_statement(mir_body: &mut mir::Body<'_>, counter_kind: CoverageKind, bb
data.statements.insert(0, statement);
}

/// Convert the Span into its file name, start line and column, and end line and column
/// Convert the Span into its file name, start line and column, and end line and column.
///
/// Line numbers and column numbers are 1-based. Unlike most column numbers emitted by
/// the compiler, these column numbers are denoted in **bytes**, because that's what
/// LLVM's `llvm-cov` tool expects to see in coverage maps.
///
/// Returns `None` if the conversion failed for some reason. This shouldn't happen,
/// but it's hard to rule out entirely (especially in the presence of complex macros
/// or other expansions), and if it does happen then skipping a span or function is
/// better than an ICE or `llvm-cov` failure that the user might have no way to avoid.
fn make_code_region(
source_map: &SourceMap,
file_name: Symbol,
span: Span,
body_span: Span,
) -> CodeRegion {
) -> Option<CodeRegion> {
debug!(
"Called make_code_region(file_name={}, span={}, body_span={})",
file_name,
source_map.span_to_diagnostic_string(span),
source_map.span_to_diagnostic_string(body_span)
);

let (file, mut start_line, mut start_col, mut end_line, mut end_col) =
source_map.span_to_location_info(span);
if span.hi() == span.lo() {
// Extend an empty span by one character so the region will be counted.
if span.hi() == body_span.hi() {
start_col = start_col.saturating_sub(1);
} else {
end_col = start_col + 1;
}
let lo = span.lo();
let hi = span.hi();

let file = source_map.lookup_source_file(lo);
if !file.contains(hi) {
debug!(?span, ?file, ?lo, ?hi, "span crosses multiple files; skipping");
return None;
}

// Column numbers need to be in bytes, so we can't use the more convenient
// `SourceMap` methods for looking up file coordinates.
let rpos_and_line_and_byte_column = |pos: BytePos| -> Option<(RelativeBytePos, usize, usize)> {
let rpos = file.relative_position(pos);
let line_index = file.lookup_line(rpos)?;
let line_start = file.lines()[line_index];
// Line numbers and column numbers are 1-based, so add 1 to each.
Some((rpos, line_index + 1, (rpos - line_start).to_usize() + 1))
};
if let Some(file) = file {
start_line = source_map.doctest_offset_line(&file.name, start_line);
end_line = source_map.doctest_offset_line(&file.name, end_line);

let (lo_rpos, mut start_line, mut start_col) = rpos_and_line_and_byte_column(lo)?;
let (hi_rpos, mut end_line, mut end_col) = rpos_and_line_and_byte_column(hi)?;

// If the span is empty, try to expand it horizontally by one character's
// worth of bytes, so that it is more visible in `llvm-cov` reports.
// We do this after resolving line/column numbers, so that empty spans at the
// end of a line get an extra column instead of wrapping to the next line.
if span.is_empty()
&& body_span.contains(span)
&& let Some(src) = &file.src
{
// Prefer to expand the end position, if it won't go outside the body span.
if hi < body_span.hi() {
let hi_rpos = hi_rpos.to_usize();
let nudge_bytes = src.ceil_char_boundary(hi_rpos + 1) - hi_rpos;
end_col += nudge_bytes;
} else if lo > body_span.lo() {
let lo_rpos = lo_rpos.to_usize();
let nudge_bytes = lo_rpos - src.floor_char_boundary(lo_rpos - 1);
// Subtract the nudge, but don't go below column 1.
start_col = start_col.saturating_sub(nudge_bytes).max(1);
}
// If neither nudge could be applied, stick with the empty span coordinates.
}
CodeRegion {

// Apply an offset so that code in doctests has correct line numbers.
// FIXME(#79417): Currently we have no way to offset doctest _columns_.
start_line = source_map.doctest_offset_line(&file.name, start_line);
end_line = source_map.doctest_offset_line(&file.name, end_line);

Some(CodeRegion {
file_name,
start_line: start_line as u32,
start_col: start_col as u32,
end_line: end_line as u32,
end_col: end_col as u32,
}
})
}

fn is_eligible_for_coverage(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_mir_transform/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
#![feature(min_specialization)]
#![feature(never_type)]
#![feature(option_get_or_insert_default)]
#![feature(round_char_boundary)]
#![feature(trusted_step)]
#![feature(try_blocks)]
#![feature(yeet_expr)]
Expand Down
53 changes: 53 additions & 0 deletions tests/coverage/unicode.cov-map
Original file line number Diff line number Diff line change
@@ -0,0 +1,53 @@
Function name: unicode::main
Raw bytes (67): 0x[01, 01, 09, 01, 05, 03, 05, 1e, 0d, 22, 09, 03, 05, 11, 1b, 1e, 0d, 22, 09, 03, 05, 09, 01, 0e, 01, 00, 0b, 05, 01, 09, 00, 0c, 03, 00, 10, 00, 1b, 05, 00, 1c, 00, 28, 22, 02, 08, 00, 25, 09, 00, 29, 00, 46, 11, 00, 47, 02, 06, 1b, 02, 06, 00, 07, 17, 02, 05, 01, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 9
- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
- expression 1 operands: lhs = Expression(0, Add), rhs = Counter(1)
- expression 2 operands: lhs = Expression(7, Sub), rhs = Counter(3)
- expression 3 operands: lhs = Expression(8, Sub), rhs = Counter(2)
- expression 4 operands: lhs = Expression(0, Add), rhs = Counter(1)
- expression 5 operands: lhs = Counter(4), rhs = Expression(6, Add)
- expression 6 operands: lhs = Expression(7, Sub), rhs = Counter(3)
- expression 7 operands: lhs = Expression(8, Sub), rhs = Counter(2)
- expression 8 operands: lhs = Expression(0, Add), rhs = Counter(1)
Number of file 0 mappings: 9
- Code(Counter(0)) at (prev + 14, 1) to (start + 0, 11)
- Code(Counter(1)) at (prev + 1, 9) to (start + 0, 12)
- Code(Expression(0, Add)) at (prev + 0, 16) to (start + 0, 27)
= (c0 + c1)
- Code(Counter(1)) at (prev + 0, 28) to (start + 0, 40)
- Code(Expression(8, Sub)) at (prev + 2, 8) to (start + 0, 37)
= ((c0 + c1) - c1)
- Code(Counter(2)) at (prev + 0, 41) to (start + 0, 70)
- Code(Counter(4)) at (prev + 0, 71) to (start + 2, 6)
- Code(Expression(6, Add)) at (prev + 2, 6) to (start + 0, 7)
= ((((c0 + c1) - c1) - c2) + c3)
- Code(Expression(5, Add)) at (prev + 2, 5) to (start + 1, 2)
= (c4 + ((((c0 + c1) - c1) - c2) + c3))

Function name: unicode::サビ
Raw bytes (9): 0x[01, 01, 00, 01, 01, 1e, 14, 00, 18]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 1
- Code(Counter(0)) at (prev + 30, 20) to (start + 0, 24)

Function name: unicode::他 (unused)
Raw bytes (9): 0x[01, 01, 00, 01, 00, 1e, 19, 00, 25]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 1
- Code(Zero) at (prev + 30, 25) to (start + 0, 37)

Function name: unicode::申し訳ございません
Raw bytes (9): 0x[01, 01, 00, 01, 01, 18, 01, 02, 02]
Number of files: 1
- file 0 => global file 1
Number of expressions: 0
Number of file 0 mappings: 1
- Code(Counter(0)) at (prev + 24, 1) to (start + 2, 2)

40 changes: 40 additions & 0 deletions tests/coverage/unicode.coverage
Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
LL| |// edition: 2021
LL| |// ignore-windows - we can't force `llvm-cov` to use ANSI escapes on Windows
LL| |// llvm-cov-flags: --use-color
LL| |
LL| |// Check that column numbers are denoted in bytes, so that they don't cause
LL| |// `llvm-cov` to fail or emit malformed output.
LL| |//
LL| |// Note that when `llvm-cov` prints ^ arrows on a subsequent line, it simply
LL| |// inserts one space character for each "column", with no understanding of
LL| |// Unicode or character widths. So those arrows will tend to be misaligned
LL| |// for non-ASCII source code, regardless of whether column numbers are code
LL| |// points or bytes.
LL| |
LL| 1|fn main() {
LL| 33| for _İ in 'А'..='Я' { /* Я */ }
^32 ^32
LL| |
LL| 1| if 申し訳ございません() && 申し訳ございません() {
^0
LL| 0| println!("true");
LL| 1| }
LL| |
LL| 1| サビ();
LL| 1|}
LL| |
LL| 1|fn 申し訳ございません() -> bool {
LL| 1| std::hint::black_box(false)
LL| 1|}
LL| |
LL| |macro_rules! macro_that_defines_a_function {
LL| | (fn $名:ident () $体:tt) => {
LL| 1| fn $名 () $体 fn 他 () {}
^0
LL| | }
LL| |}
LL| |
LL| |macro_that_defines_a_function! {
LL| | fn サビ() {}
LL| |}

36 changes: 36 additions & 0 deletions tests/coverage/unicode.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
// edition: 2021
// ignore-windows - we can't force `llvm-cov` to use ANSI escapes on Windows
// llvm-cov-flags: --use-color

// Check that column numbers are denoted in bytes, so that they don't cause
// `llvm-cov` to fail or emit malformed output.
//
// Note that when `llvm-cov` prints ^ arrows on a subsequent line, it simply
// inserts one space character for each "column", with no understanding of
// Unicode or character widths. So those arrows will tend to be misaligned
// for non-ASCII source code, regardless of whether column numbers are code
// points or bytes.

fn main() {
forin 'А'..='Я' { /* Я */ }

if 申し訳ございません() && 申し訳ございません() {
println!("true");
}

サビ();
}

fn 申し訳ございません() -> bool {
std::hint::black_box(false)
}

macro_rules! macro_that_defines_a_function {
(fn $名:ident () $体:tt) => {
fn $名 () $体 fn() {}
}
}

macro_that_defines_a_function! {
fn サビ() {}
}

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