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fix: check segment name when matching symbol neighbors #558

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Merged
trevor-e merged 1 commit into from
Jan 30, 2026
+53 −55
Merged

fix: check segment name when matching symbol neighbors #558

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108 changes: 53 additions & 55 deletions src/launchpad/size/symbols/macho_symbol_sizes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,12 +3,18 @@
from typing import NamedTuple

import lief
import sentry_sdk

from launchpad.utils.logging import get_logger

logger = get_logger(__name__)


def _decode_name(raw_name: str | bytes) -> str:
"""Decode a name from bytes if necessary."""
return raw_name.decode("utf-8", errors="replace") if isinstance(raw_name, bytes) else str(raw_name)


class _SymbolSizeData(NamedTuple):
name: str
section_name: str | None
Expand All @@ -34,19 +40,16 @@ def __init__(self, binary: lief.MachO.Binary) -> None:

def get_symbol_sizes(self) -> list[SymbolSize]:
"""Get the symbol sizes."""
symbol_data = list(self._symbol_sizes(self.binary))

symbol_sizes: list[SymbolSize] = []
for data in symbol_data:
symbol_sizes.append(
SymbolSize(
mangled_name=data.name,
section_name=data.section_name,
segment_name=data.segment_name,
address=data.address,
size=data.size,
)
symbol_sizes = [
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@trevor-e trevor-e Jan 30, 2026

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There's some light cleanup mixed in here as well, left a comment on the bug fix.

SymbolSize(
mangled_name=data.name,
section_name=data.section_name,
segment_name=data.segment_name,
address=data.address,
size=data.size,
)
for data in self._symbol_sizes(self.binary)
]

logger.debug(f"Found {len(symbol_sizes)} symbol sizes")
symbol_sizes.sort(key=lambda x: x.size, reverse=True)
Expand Down Expand Up @@ -78,65 +81,60 @@ def _symbol_sizes(self, bin: lief.MachO.Binary) -> Generator[_SymbolSizeData]:

# sort symbols by their address so we can calculate the distance between them
syms = sorted((s for s in bin.symbols if self._is_measurable(s)), key=lambda s: s.value)
num_syms = len(syms)

cached_section = None
cached_section_va = None

for idx, sym in enumerate(syms):
start = sym.value

section = bin.section_from_virtual_address(start)
if section:
max_section_addr = section.virtual_address + section.size
raw_name = section.name
section_name = (
raw_name.decode("utf-8", errors="replace") if isinstance(raw_name, bytes) else str(raw_name)
)

if section.segment:
raw_seg_name = section.segment.name
segment_name = (
raw_seg_name.decode("utf-8", errors="replace")
if isinstance(raw_seg_name, bytes)
else str(raw_seg_name)
)
else:
segment_name = None
if cached_section_va == start:
section = cached_section
else:
max_section_addr = None
section_name = None
segment_name = None
section = bin.section_from_virtual_address(start)

if not section:
logger.warning("size.macho.symbol_not_found_in_section", extra={"symbol": sym.name})
cached_section = None
cached_section_va = None
continue

# Only calculate the distance between symbols in the same section
if max_section_addr:
if idx + 1 < len(syms):
next_sym = syms[idx + 1]
next_sym_section = bin.section_from_virtual_address(next_sym.value)
end = (
next_sym.value
if next_sym_section and next_sym_section.name == section.name
else max_section_addr
)
else:
end = max_section_addr
max_section_addr = section.virtual_address + section.size
section_name = _decode_name(section.name)
segment_name = _decode_name(section.segment.name) if section.segment else None

if idx + 1 < num_syms:
next_sym = syms[idx + 1]
next_sym_section = bin.section_from_virtual_address(next_sym.value)
cached_section = next_sym_section
cached_section_va = next_sym.value
same_section = (
next_sym_section
and next_sym_section.segment
and next_sym_section.segment.name == section.segment.name
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@trevor-e trevor-e Jan 30, 2026

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This is the core fix, we had a case where a symbol got compared to a section in a different segment.

and next_sym_section.name == section.name
)
end = next_sym.value if same_section else max_section_addr
else:
end = syms[idx + 1].value
end = max_section_addr
cached_section = None
cached_section_va = None

# Convert virtual addresses to file offsets to calculate the disk size
offset_end = bin.virtual_address_to_offset(end)
offset_start = bin.virtual_address_to_offset(start)
size = 0
if not isinstance(offset_end, lief.lief_errors) and not isinstance(offset_start, lief.lief_errors):
raw_size = offset_end - offset_start
if raw_size < 0:
logger.warning(
"size.macho.negative_symbol_size",
extra={
"symbol": sym.name,
"offset_start": offset_start,
"offset_end": offset_end,
"section": section_name,
},
)
error_context = {
"symbol": sym.name,
"offset_start": offset_start,
"offset_end": offset_end,
"section": section_name,
}
logger.warning("size.macho.negative_symbol_size", extra=error_context)
sentry_sdk.capture_message("size.macho.negative_symbol_size", level="error", extras=error_context)
size = max(0, raw_size)
else:
logger.warning(f"Failed to calculate size for symbol {sym.name}")
Expand Down
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