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feat(r8): Add line span expansion and outside-range fallback #86

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romtsn merged 2 commits into from
Feb 16, 2026
+100 −5
Merged

feat(r8): Add line span expansion and outside-range fallback #86

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b4acde2
feat(r8): Add line span expansion and outside-range fallback
romtsn Feb 9, 2026
ea0879b
fix: Cap span expansion at u16::MAX (65535) line range
romtsn Feb 16, 2026
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72 changes: 67 additions & 5 deletions src/cache/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,15 @@ use crate::mapper::{format_cause, format_frames, format_throwable};
use crate::utils::{class_name_to_descriptor, extract_class_name, synthesize_source_file};
use crate::{java, stacktrace, DeobfuscatedSignature, StackFrame, StackTrace, Throwable};

/// Maximum number of frames emitted by span expansion for a single mapping entry.
///
/// R8 uses `0:65535` as the catch-all range for methods with a single unique position:
/// <https://r8.googlesource.com/r8/+/refs/heads/main/doc/retrace.md#catch-all-range-for-methods-with-a-single-unique-position>
///
/// No real method would span more lines than this, so ranges exceeding this cap
/// are treated as malformed and fall through to single-line handling.
const MAX_SPAN_EXPANSION: u32 = 65_535;

pub use raw::{ProguardCache, PRGCACHE_VERSION};

/// Result of looking up member mappings for a frame.
Expand Down Expand Up @@ -838,6 +847,8 @@ pub struct RemappedFrameIter<'r, 'data> {
had_mappings: bool,
/// Whether this method has any line-based mappings.
has_line_info: bool,
/// Whether any frame was successfully matched by iterate_with_lines.
matched_any: bool,
/// The source file of the outer class for synthesis.
outer_source_file: Option<&'data str>,
}
Expand All @@ -851,6 +862,7 @@ impl<'r, 'data> RemappedFrameIter<'r, 'data> {
skip_count: 0,
had_mappings: false,
has_line_info: false,
matched_any: false,
outer_source_file: None,
}
}
Expand All @@ -871,6 +883,7 @@ impl<'r, 'data> RemappedFrameIter<'r, 'data> {
skip_count,
had_mappings,
has_line_info,
matched_any: false,
outer_source_file,
}
}
Expand All @@ -883,6 +896,7 @@ impl<'r, 'data> RemappedFrameIter<'r, 'data> {
skip_count: 0,
had_mappings: false,
has_line_info: false,
matched_any: false,
outer_source_file: None,
}
}
Expand Down Expand Up @@ -932,9 +946,20 @@ impl<'r, 'data> RemappedFrameIter<'r, 'data> {
&mut members,
self.outer_source_file,
self.has_line_info,
&mut self.pending_frames,
);
self.inner = Some((cache, frame, members));
mapped
if mapped.is_some() {
self.matched_any = true;
self.inner = Some((cache, frame, members));
mapped
} else if !self.matched_any && self.has_line_info {
// Outside-range fallback: no member matched the frame line.
// Remap only the class name, keeping the obfuscated method name
// and the original line.
Some(cache.remap_class_only(&frame, self.outer_source_file))
} else {
None
}
} else {
let mapped =
iterate_without_lines(cache, &mut frame, &mut members, self.outer_source_file);
Expand Down Expand Up @@ -965,6 +990,7 @@ fn iterate_with_lines<'a>(
members: &mut std::slice::Iter<'_, raw::Member>,
outer_source_file: Option<&str>,
has_line_info: bool,
pending_frames: &mut Vec<StackFrame<'a>>,
) -> Option<StackFrame<'a>> {
let frame_line = frame.line.unwrap_or(0);
for member in members {
Expand All @@ -974,10 +1000,46 @@ fn iterate_with_lines<'a>(
}
// If the mapping entry has no line range, determine output line.
if member.endline().unwrap_or(0) == 0 {
let output_line = if member.original_startline().is_none() {
if member.original_startline().is_none() {
// Bare method mapping: pass through frame line.
frame.line
} else if member.original_startline().unwrap_or(0) > 0 {
return map_member_without_lines(
cache,
frame,
member,
outer_source_file,
frame.line,
);
}
// Span expansion: if the original range spans multiple lines,
// emit one frame per original line.
if member.original_endline != u32::MAX
&& member.original_endline > member.original_startline().unwrap_or(0)
&& (member.original_endline - member.original_startline().unwrap_or(0))
<= MAX_SPAN_EXPANSION
{
let first_line = member.original_startline().unwrap_or(0) as usize;
let last_line = member.original_endline as usize;
let mut first_frame = None;
for line in first_line..=last_line {
if let Some(f) = map_member_without_lines(
cache,
frame,
member,
outer_source_file,
Some(line),
) {
if first_frame.is_none() {
first_frame = Some(f);
} else {
pending_frames.push(f);
}
}
}
// Reverse so pop() drains in ascending line order.
pending_frames.reverse();
return first_frame;
}
let output_line = if member.original_startline().unwrap_or(0) > 0 {
Some(member.original_startline().unwrap_or(0) as usize)
} else {
None
Expand Down
33 changes: 33 additions & 0 deletions src/mapper.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,15 @@ use std::fmt;
use std::fmt::{Error as FmtError, Write};
use std::iter::FusedIterator;

/// Maximum number of frames emitted by span expansion for a single mapping entry.
///
/// R8 uses `0:65535` as the catch-all range for methods with a single unique position:
/// <https://r8.googlesource.com/r8/+/refs/heads/main/doc/retrace.md#catch-all-range-for-methods-with-a-single-unique-position>
///
/// No real method would span more lines than this, so ranges exceeding this cap
/// are treated as malformed and fall through to single-line handling.
const MAX_SPAN_EXPANSION: usize = 65_535;

use crate::builder::{
Member, MethodReceiver, ParsedProguardMapping, RewriteAction, RewriteCondition, RewriteRule,
};
Expand Down Expand Up @@ -697,6 +706,22 @@ impl<'s> ProguardMapper<'s> {
collected.rewrite_rules.extend(member.rewrite_rules.iter());
continue;
}
// Span expansion: if the original range spans multiple lines,
// emit one frame per original line.
if let Some(oe) = member.original_endline {
let os = member.original_startline.unwrap_or(0);
if oe > os && (oe - os) <= MAX_SPAN_EXPANSION {
for line in os..=oe {
collected.frames.push(map_member_without_lines(
&frame,
member,
Some(line),
));
}
collected.rewrite_rules.extend(member.rewrite_rules.iter());
continue;
}
}
// Single-line: use original_startline if > 0, else None.
let output_line = if member.original_startline.unwrap_or(0) > 0 {
member.original_startline
Expand All @@ -712,6 +737,14 @@ impl<'s> ProguardMapper<'s> {
collected.rewrite_rules.extend(member.rewrite_rules.iter());
}
}

// Outside-range fallback: if we had line mappings but nothing matched,
// remap only the class name, keeping the obfuscated method name and original line.
if collected.frames.is_empty() && has_line_info {
collected
.frames
.push(remap_class_only(&frame, frame.file()));
}
} else {
for member in mapping_entries {
// For parameter-based lookups, use original_startline if > 0, else None
Expand Down
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