addr2line: detect clang version and dispatch to modern or legacy resolver#4973
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TianlongLiang wants to merge 1 commit into
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addr2line: detect clang version and dispatch to modern or legacy resolver#4973TianlongLiang wants to merge 1 commit into
TianlongLiang wants to merge 1 commit into
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…able overlay
Refactor the wasm symbolicator to make its DWARF workaround explicit
and unconditional. addr2line.py runs one llvm-symbolizer -f -i call
per address, then overlays the outermost frame's function name from a
startup-built DWARF interval table.
The overlay exists because llvm-symbolizer returns the wrong outermost
function name on wasm targets for two independent, source-verified
reasons:
- Symbol-table override on the outermost frame (LLVM design, not a
bug). symbolizeInlinedCode in llvm/lib/DebugInfo/Symbolize/
SymbolizableObjectFile.cpp unconditionally rewrites the outermost
frame's FunctionName from getNameFromSymbolTable when
FunctionNameKind::LinkageName and UseSymbolTable are both set, which
is the default. Inline frames come from getInliningInfoForAddress
(a different code path) and are provably immune.
- AddrDieMap invariant violation from wasm-opt -Oz -g DCE ghosts.
LocationUpdater::getNewFuncStart in binaryen's src/wasm/wasm-debug.cpp
returns 0 as a tombstone when an old address doesn't map to a
surviving IR node, and updateDIE writes it into DW_AT_low_pc without
removing the DW_TAG_subprogram. LLVM's updateAddressDieMap in
DWARFUnit.cpp requires child ranges ⊆ parent ranges; these ghosts
break that invariant so the map's upper_bound − 1 lookup returns
an insertion-order-dependent DIE.
Both mechanisms produce the same "wrong outermost frame name" symptom
and both apply on any supported wasi-sdk, so the overlay runs on every
resolution. build_subprogram_intervals filters three DIE classes at
parse time: DW_AT_declaration=true (forward decls), low_pc == 0
(DWARF Code-section-relative zero is the function-count LEB, not a
real body — this is the DCE-ghost pattern), and high_pc <= low_pc
(degenerate ranges). The innermost covering DW_TAG_subprogram wins.
Also includes accumulated tool improvements:
- --mode flag {interp,aot,fast-interp} for different runtime offset
conventions (interp post-advance, aot at-instruction-start,
fast-interp's transformed in-memory bytecode)
- Inline frame annotation "(inlined into <next>)" for clarity
- llvm-symbolizer preferred over llvm-addr2line for column info
- Fallback for offset=0 (trap at function entry; frame_ip not captured)
- Last-resort function-index name fallback when DWARF lacks PC ranges
Full design rationale, source citations, and empirical truth table in
test-tools/addr2line/README.md.
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Refactor the wasm symbolicator to make its toolchain workarounds explicit. addr2line.py now detects the wasi-sdk's clang major version at startup and routes per-frame address resolution to one of:
resolve_address_modern (clang >= 22, wasi-sdk 33+): single llvm-symbolizer call per address. The symbolizer handles address-to-name correctly on this clang.
resolve_address_legacy (clang < 22 or unknown): llvm-symbolizer call + llvm-dwarfdump --lookup overlay to fix the outermost function name. Older clang versions emit wasm DWARF that confuses llvm-symbolizer's address-to-name resolver for some addresses (e.g., reports 'recurse' as 'free'). --lookup goes through a different DWARF traversal path that handles them.
The dispatch decision is logged once to stderr so users can see which path was taken without polluting stdout. Stdout is byte- identical between paths for non-buggy inputs.
Also includes accumulated improvements: