[WebAssembly] Add symbol information for shared libraries (#75238)
The current (experimental) spec for WebAssembly shared libraries does not include a full symbol table like the object format. This change extracts symbol information from the normal wasm exports. This is the first step in having the linker report undefined symbols when linking with shared libraries. The current behaviour is to ignore all undefined symbols when linking with `-pie` or `-shared`. See https://github.com/emscripten-core/emscripten/issues/18198
This commit is contained in:
Sam Clegg
GitHub
parent
2c27013fa9
commit
4e8cb01b01
4 changed files with 186 additions and 4 deletions
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@ -144,7 +144,6 @@ public:
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ArrayRef<wasm::WasmGlobal> globals() const { return Globals; }
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ArrayRef<wasm::WasmTag> tags() const { return Tags; }
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ArrayRef<wasm::WasmExport> exports() const { return Exports; }
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ArrayRef<WasmSymbol> syms() const { return Symbols; }
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const wasm::WasmLinkingData &linkingData() const { return LinkingData; }
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uint32_t getNumberOfSymbols() const { return Symbols.size(); }
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ArrayRef<wasm::WasmElemSegment> elements() const { return ElemSegments; }
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@ -599,6 +599,10 @@ Error WasmObjectFile::parseLinkingSection(ReadContext &Ctx) {
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Error WasmObjectFile::parseLinkingSectionSymtab(ReadContext &Ctx) {
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uint32_t Count = readVaruint32(Ctx);
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// Clear out any symbol information that was derived from the exports
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// section.
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LinkingData.SymbolTable.clear();
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Symbols.clear();
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LinkingData.SymbolTable.reserve(Count);
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Symbols.reserve(Count);
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StringSet<> SymbolNames;
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@ -1290,37 +1294,75 @@ Error WasmObjectFile::parseGlobalSection(ReadContext &Ctx) {
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Error WasmObjectFile::parseExportSection(ReadContext &Ctx) {
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uint32_t Count = readVaruint32(Ctx);
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Exports.reserve(Count);
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LinkingData.SymbolTable.reserve(Count);
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Symbols.reserve(Count);
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for (uint32_t I = 0; I < Count; I++) {
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wasm::WasmExport Ex;
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Ex.Name = readString(Ctx);
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Ex.Kind = readUint8(Ctx);
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Ex.Index = readVaruint32(Ctx);
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const wasm::WasmSignature *Signature = nullptr;
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const wasm::WasmGlobalType *GlobalType = nullptr;
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const wasm::WasmTableType *TableType = nullptr;
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wasm::WasmSymbolInfo Info;
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Info.Name = Ex.Name;
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Info.Flags = 0;
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switch (Ex.Kind) {
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case wasm::WASM_EXTERNAL_FUNCTION:
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case wasm::WASM_EXTERNAL_FUNCTION: {
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if (!isDefinedFunctionIndex(Ex.Index))
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return make_error<GenericBinaryError>("invalid function export",
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object_error::parse_failed);
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getDefinedFunction(Ex.Index).ExportName = Ex.Name;
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Info.Kind = wasm::WASM_SYMBOL_TYPE_FUNCTION;
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Info.ElementIndex = Ex.Index;
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unsigned FuncIndex = Info.ElementIndex - NumImportedFunctions;
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wasm::WasmFunction &Function = Functions[FuncIndex];
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Signature = &Signatures[Function.SigIndex];
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break;
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case wasm::WASM_EXTERNAL_GLOBAL:
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}
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case wasm::WASM_EXTERNAL_GLOBAL: {
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if (!isValidGlobalIndex(Ex.Index))
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return make_error<GenericBinaryError>("invalid global export",
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object_error::parse_failed);
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Info.Kind = wasm::WASM_SYMBOL_TYPE_DATA;
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uint64_t Offset = 0;
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if (isDefinedGlobalIndex(Ex.Index)) {
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auto Global = getDefinedGlobal(Ex.Index);
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if (!Global.InitExpr.Extended) {
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auto Inst = Global.InitExpr.Inst;
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if (Inst.Opcode == wasm::WASM_OPCODE_I32_CONST) {
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Offset = Inst.Value.Int32;
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} else if (Inst.Opcode == wasm::WASM_OPCODE_I64_CONST) {
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Offset = Inst.Value.Int64;
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}
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}
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}
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Info.DataRef = wasm::WasmDataReference{0, Offset, 0};
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break;
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}
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case wasm::WASM_EXTERNAL_TAG:
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if (!isValidTagIndex(Ex.Index))
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return make_error<GenericBinaryError>("invalid tag export",
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object_error::parse_failed);
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Info.Kind = wasm::WASM_SYMBOL_TYPE_TAG;
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Info.ElementIndex = Ex.Index;
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break;
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case wasm::WASM_EXTERNAL_MEMORY:
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break;
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case wasm::WASM_EXTERNAL_TABLE:
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Info.Kind = wasm::WASM_SYMBOL_TYPE_TABLE;
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break;
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default:
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return make_error<GenericBinaryError>("unexpected export kind",
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object_error::parse_failed);
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}
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Exports.push_back(Ex);
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if (Ex.Kind != wasm::WASM_EXTERNAL_MEMORY) {
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LinkingData.SymbolTable.emplace_back(Info);
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Symbols.emplace_back(LinkingData.SymbolTable.back(), GlobalType,
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TableType, Signature);
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LLVM_DEBUG(dbgs() << "Adding symbol: " << Symbols.back() << "\n");
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}
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}
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if (Ctx.Ptr != Ctx.End)
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return make_error<GenericBinaryError>("export section ended prematurely",
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@ -1644,6 +1686,8 @@ uint64_t WasmObjectFile::getWasmSymbolValue(const WasmSymbol &Sym) const {
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return Segment.Offset.Inst.Value.Int32 + Sym.Info.DataRef.Offset;
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} else if (Segment.Offset.Inst.Opcode == wasm::WASM_OPCODE_I64_CONST) {
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return Segment.Offset.Inst.Value.Int64 + Sym.Info.DataRef.Offset;
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} else if (Segment.Offset.Inst.Opcode == wasm::WASM_OPCODE_GLOBAL_GET) {
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return Sym.Info.DataRef.Offset;
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} else {
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llvm_unreachable("unknown init expr opcode");
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}
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69
llvm/test/tools/llvm-nm/wasm/dylink.yaml
Normal file
69
llvm/test/tools/llvm-nm/wasm/dylink.yaml
Normal file
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@ -0,0 +1,69 @@
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# RUN: yaml2obj %s -o %t.so
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# RUN: llvm-nm %t.so | FileCheck %s
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#
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# CHECK: 00000001 T my_func_export
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# CHECK: 0000002a D my_global_export
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--- !WASM
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FileHeader:
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Version: 0x1
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Sections:
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- Type: CUSTOM
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Name: dylink.0
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MemorySize: 15
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MemoryAlignment: 0
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TableSize: 0
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TableAlignment: 0
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Needed: []
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- Type: TYPE
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Signatures:
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- Index: 0
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ParamTypes: []
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ReturnTypes: []
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- Type: IMPORT
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Imports:
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- Module: env
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Field: foo
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Kind: FUNCTION
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SigIndex: 0
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- Module: env
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Field: bar
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Kind: GLOBAL
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GlobalType: I32
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GlobalMutable: true
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- Module: env
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Field: memory
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Kind: MEMORY
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Memory:
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Minimum: 0x1
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- Type: FUNCTION
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FunctionTypes: [ 0 ]
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- Type: GLOBAL
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Globals:
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- Index: 1
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Mutable: false
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Type: I32
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InitExpr:
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Opcode: I32_CONST
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Value: 42
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- Type: EXPORT
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Exports:
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- Name: my_func_export
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Kind: FUNCTION
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Index: 1
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- Name: my_global_export
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Kind: GLOBAL
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Index: 1
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- Type: CODE
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Functions:
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- Index: 1
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Locals:
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Body: 00
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- Type: DATA
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Segments:
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- SectionOffset: 0
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InitFlags: 0
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Offset:
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Opcode: I32_CONST
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Value: 0
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Content: ''
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70
llvm/test/tools/llvm-objdump/wasm/dylink-symbol-table.yaml
Normal file
70
llvm/test/tools/llvm-objdump/wasm/dylink-symbol-table.yaml
Normal file
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@ -0,0 +1,70 @@
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# RUN: yaml2obj %s -o %t.so
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# RUN: llvm-objdump -t %t.so | FileCheck %s
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#
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# CHECK: SYMBOL TABLE:
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# CHECK-NEXT: 00000001 g F CODE my_func_export
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# CHECK-NEXT: 0000002a g O DATA my_global_export
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--- !WASM
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FileHeader:
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Version: 0x1
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Sections:
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- Type: CUSTOM
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Name: dylink.0
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MemorySize: 15
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MemoryAlignment: 0
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TableSize: 0
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TableAlignment: 0
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Needed: []
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- Type: TYPE
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Signatures:
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- Index: 0
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ParamTypes: []
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ReturnTypes: []
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- Type: IMPORT
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Imports:
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- Module: env
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Field: foo
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Kind: FUNCTION
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SigIndex: 0
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- Module: env
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Field: bar
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Kind: GLOBAL
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GlobalType: I32
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GlobalMutable: true
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- Module: env
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Field: memory
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Kind: MEMORY
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Memory:
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Minimum: 0x1
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- Type: FUNCTION
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FunctionTypes: [ 0 ]
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- Type: GLOBAL
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Globals:
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- Index: 1
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Mutable: false
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Type: I32
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InitExpr:
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Opcode: I32_CONST
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Value: 42
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- Type: EXPORT
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Exports:
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- Name: my_func_export
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Kind: FUNCTION
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Index: 1
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- Name: my_global_export
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Kind: GLOBAL
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Index: 1
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- Type: CODE
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Functions:
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- Index: 1
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Locals:
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Body: 00
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- Type: DATA
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Segments:
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- SectionOffset: 0
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InitFlags: 0
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Offset:
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Opcode: I32_CONST
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Value: 0
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Content: ''
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