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wasm-linker: discard symbol when both undefined

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During symbol resolution when both symbols are undefined, we must
discard the new symbol with a reference to the existing symbol. This
ensures the original symbol remains undefined. This fixes symbol
resolution when linking with WASI-libC.
This commit is contained in:
Luuk de Gram 2023-01-09 19:22:55 +01:00
parent cbbf8c8a2d
commit 2339b25fd4
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GPG Key ID: A8CFE58E4DC7D664
1 changed files with 33 additions and 22 deletions
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55
src/link/Wasm.zig
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@ -600,27 +600,34 @@ fn resolveSymbolsInObject(wasm: *Wasm, object_index: u16) !void {
}
if (existing_sym.isUndefined() and symbol.isUndefined()) {
const existing_name = if (existing_loc.file) |file_index| blk: {
const obj = wasm.objects.items[file_index];
const name_index = obj.findImport(symbol.tag.externalType(), existing_sym.index).module_name;
break :blk obj.string_table.get(name_index);
} else blk: {
const name_index = wasm.imports.get(existing_loc).?.module_name;
break :blk wasm.string_table.get(name_index);
};
// only verify module/import name for function symbols
if (symbol.tag == .function) {
const existing_name = if (existing_loc.file) |file_index| blk: {
const obj = wasm.objects.items[file_index];
const name_index = obj.findImport(symbol.tag.externalType(), existing_sym.index).module_name;
break :blk obj.string_table.get(name_index);
} else blk: {
const name_index = wasm.imports.get(existing_loc).?.module_name;
break :blk wasm.string_table.get(name_index);
};
const module_index = object.findImport(symbol.tag.externalType(), symbol.index).module_name;
const module_name = object.string_table.get(module_index);
if (!mem.eql(u8, existing_name, module_name)) {
log.err("symbol '{s}' module name mismatch. Expected '{s}', but found '{s}'", .{
sym_name,
existing_name,
module_name,
});
log.err(" first definition in '{s}'", .{existing_file_path});
log.err(" next definition in '{s}'", .{object.name});
return error.ModuleNameMismatch;
const module_index = object.findImport(symbol.tag.externalType(), symbol.index).module_name;
const module_name = object.string_table.get(module_index);
if (!mem.eql(u8, existing_name, module_name)) {
log.err("symbol '{s}' module name mismatch. Expected '{s}', but found '{s}'", .{
sym_name,
existing_name,
module_name,
});
log.err(" first definition in '{s}'", .{existing_file_path});
log.err(" next definition in '{s}'", .{object.name});
return error.ModuleNameMismatch;
}
}
// both undefined so skip overwriting existing symbol and discard the new symbol
try wasm.discarded.put(wasm.base.allocator, location, existing_loc);
continue;
}
if (existing_sym.tag == .global) {
@ -646,8 +653,10 @@ fn resolveSymbolsInObject(wasm: *Wasm, object_index: u16) !void {
}
}
// when both symbols are weak, we skip overwriting
if (existing_sym.isWeak() and symbol.isWeak()) {
// when both symbols are weak, we skip overwriting unless the existing
// symbol is weak and the new one isn't, in which case we *do* overwrite it.
if (existing_sym.isWeak() and symbol.isWeak()) blk: {
if (existing_sym.isUndefined() and !symbol.isUndefined()) break :blk;
try wasm.discarded.put(wasm.base.allocator, location, existing_loc);
continue;
}
@ -1935,7 +1944,9 @@ fn setupStart(wasm: *Wasm) !void {
return error.MissingSymbol;
};
const symbol_loc = wasm.globals.get(symbol_name_offset).?;
const symbol_loc = wasm.globals.get(symbol_name_offset) orelse {
log.err("Entry symbol '{s}' not found", .{entry_name});
};
const symbol = symbol_loc.getSymbol(wasm);
if (symbol.tag != .function) {
log.err("Entry symbol '{s}' is not a function", .{entry_name});