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kripkenkripken
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New fuzzer (#1126)
This adds a new method of fuzzing, "translate to fuzz" which means we consider the input to be a stream of data that we translate into a valid wasm module. It's sort of like a random seed for a process that creates a random wasm module. By using the input that way, we can explore the space of valid wasm modules quickly, and it makes afl-fuzz integration easy. Also adds a "fuzz binary" option which is similar to "fuzz execution". It makes wasm-opt not only execute the code before and after opts, but also write to binary and read from it, helping to fuzz the binary format.
1 parent 5295929 commit 4216894

18 files changed

Lines changed: 2900 additions & 85 deletions

‎auto_update_tests.py‎

Lines changed: 8 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -45,7 +45,6 @@
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cmd += ['--source-map', os.path.join('test', wasm + '.map'), '-o', 'a.wasm']
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run_command(cmd)
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48-
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for dot_s_dir in ['dot_s', 'llvm_autogenerated']:
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for s in sorted(os.listdir(os.path.join('test', dot_s_dir))):
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if not s.endswith('.s'): continue
@@ -102,6 +101,14 @@
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cmd = WASM_OPT + opts + ['split.wast', '--print']
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actual += run_command(cmd)
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with open(os.path.join('test', 'passes', passname + ('.bin' if binary else '') + '.txt'), 'w') as o: o.write(actual)
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if 'emit-js-wrapper' in t:
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with open('a.js') as i:
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with open(t + '.js', 'w') as o:
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o.write(i.read())
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if 'emit-spec-wrapper' in t:
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with open('a.wat') as i:
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with open(t + '.wat', 'w') as o:
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o.write(i.read())
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106113
print '\n[ checking wasm-opt -o notation... ]\n'
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‎check.py‎

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Original file line numberDiff line numberDiff line change
@@ -106,6 +106,15 @@
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fail_if_not_identical(actual, open(os.path.join('test', 'passes', passname + ('.bin' if binary else '') + '.txt'), 'rb').read())
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if 'emit-js-wrapper' in t:
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with open('a.js') as actual:
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with open(t + '.js') as expected:
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fail_if_not_identical(actual.read(), expected.read())
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if 'emit-spec-wrapper' in t:
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with open('a.wat') as actual:
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with open(t + '.wat') as expected:
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fail_if_not_identical(actual.read(), expected.read())
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print '[ checking asm2wasm testcases... ]\n'
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for asm in tests:

‎src/tools/execution-results.h‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,117 @@
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/*
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* Copyright 2017 WebAssembly Community Group participants
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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//
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// Shared execution result checking code
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//
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#include "wasm.h"
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#include "shell-interface.h"
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namespace wasm {
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static bool areBitwiseEqual(Literal a, Literal b) {
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if (a == b) return true;
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// accept equal nans if equal in all bits
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if (a.type != b.type) return false;
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if (a.type == f32) {
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return a.reinterpreti32() == b.reinterpreti32();
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} else if (a.type == f64) {
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return a.reinterpreti64() == b.reinterpreti64();
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}
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return false;
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}
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// gets execution results from a wasm module. this is useful for fuzzing
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//
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// we can only get results when there are no imports. we then call each method
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// that has a result, with some values
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struct ExecutionResults {
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std::map<Name, Literal> results;
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// get results of execution
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void get(Module& wasm) {
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if (wasm.imports.size() > 0) {
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std::cout << "[fuzz-exec] imports, so quitting\n";
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return;
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}
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for (auto& func : wasm.functions) {
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if (func->result != none) {
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// this has a result
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results[func->name] = run(func.get(), wasm);
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std::cout << "[fuzz-exec] note result: " << func->name.str << " => " << results[func->name] << '\n';
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} else {
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// no result, run it anyhow (it might modify memory etc.)
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run(func.get(), wasm);
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std::cout << "[fuzz-exec] no result for void func: " << func->name.str << '\n';
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}
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}
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std::cout << "[fuzz-exec] " << results.size() << " results noted\n";
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}
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// get current results and check them against previous ones
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void check(Module& wasm) {
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ExecutionResults optimizedResults;
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optimizedResults.get(wasm);
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if (optimizedResults != *this) {
70+
std::cout << "[fuzz-exec] optimization passes changed execution results";
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abort();
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}
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std::cout << "[fuzz-exec] " << results.size() << " results match\n";
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}
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bool operator==(ExecutionResults& other) {
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for (auto& iter : results) {
78+
auto name = iter.first;
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if (other.results.find(name) != other.results.end()) {
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std::cout << "[fuzz-exec] comparing " << name << '\n';
81+
if (!areBitwiseEqual(results[name], other.results[name])) {
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std::cout << "not identical!\n";
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abort();
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}
85+
}
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}
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return true;
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}
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bool operator!=(ExecutionResults& other) {
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return !((*this) == other);
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}
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Literal run(Function* func, Module& wasm) {
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ShellExternalInterface interface;
96+
try {
97+
ModuleInstance instance(wasm, &interface);
98+
LiteralList arguments;
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// init hang support, if present
100+
if (wasm.getFunctionOrNull("hangLimitInitializer")) {
101+
instance.callFunction("hangLimitInitializer", arguments);
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}
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// call the method
104+
for (WasmType param : func->params) {
105+
// zeros in arguments TODO: more?
106+
arguments.push_back(Literal(param));
107+
}
108+
return instance.callFunction(func->name, arguments);
109+
} catch (const TrapException&) {
110+
// may throw in instance creation (init of offsets) or call itself
111+
return Literal();
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}
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}
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};
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} // namespace wasm
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‎src/tools/js-wrapper.h‎

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/*
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* Copyright 2017 WebAssembly Community Group participants
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
14+
* limitations under the License.
15+
*/
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//
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// Emit a JavaScript wrapper to run a wasm module with some test
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// values, useful for fuzzing.
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//
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namespace wasm {
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static std::string generateJSWrapper(Module& wasm) {
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std::string ret;
26+
ret += "if (typeof console === 'undefined') {\n"
27+
" console = { log: print };\n"
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"}\n"
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"var binary;\n"
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"if (typeof process === 'object' && typeof require === 'function' /* node.js detection */) {\n"
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" var args = process.argv.slice(2);\n"
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" binary = require('fs').readFileSync(args[0]);\n"
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" if (!binary.buffer) binary = new Uint8Array(binary);\n"
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"} else {\n"
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" var args;\n"
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" if (typeof scriptArgs != 'undefined') {\n"
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" args = scriptArgs;\n"
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" } else if (typeof arguments != 'undefined') {\n"
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" args = arguments;\n"
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" }\n"
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" if (typeof readbuffer === 'function') {\n"
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" binary = new Uint8Array(readbuffer(args[0]));\n"
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" } else {\n"
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" binary = read(args[0], 'binary');\n"
45+
" }\n"
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"}\n"
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"var instance = new WebAssembly.Instance(new WebAssembly.Module(binary), {});\n";
48+
for (auto& exp : wasm.exports) {
49+
auto* func = wasm.getFunctionOrNull(exp->value);
50+
if (!func) continue; // something exported other than a function
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auto bad = false; // check for things we can't support
52+
for (WasmType param : func->params) {
53+
if (param == i64) bad = true;
54+
}
55+
if (func->result == i64) bad = true;
56+
if (bad) continue;
57+
ret += "if (instance.exports.hangLimitInitializer) instance.exports.hangLimitInitializer();\n";
58+
ret += "try {\n";
59+
ret += std::string(" console.log('calling: ") + exp->name.str + "');\n";
60+
if (func->result != none) {
61+
ret += " console.log(' result: ' + ";
62+
}
63+
ret += std::string("instance.exports.") + exp->name.str + "(";
64+
bool first = true;
65+
for (WasmType param : func->params) {
66+
WASM_UNUSED(param);
67+
// zeros in arguments TODO more?
68+
if (first) {
69+
first = false;
70+
} else {
71+
ret += ", ";
72+
}
73+
ret += "0";
74+
}
75+
ret += ")";
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if (func->result != none) {
77+
ret += ")"; // for console.log
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}
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ret += ";\n";
80+
ret += "} catch (e) {\n";
81+
ret += " console.log(' exception: ' + e);\n";
82+
ret += "}\n";
83+
}
84+
ret += "console.log('done.')\n";
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return ret;
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}
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88+
} // namespace wasm
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‎src/tools/spec-wrapper.h‎

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/*
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* Copyright 2017 WebAssembly Community Group participants
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
11+
* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
15+
*/
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//
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// Emit a wasm spec interpreter wrapper to run a wasm module with some test
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// values, useful for fuzzing.
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//
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namespace wasm {
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static std::string generateSpecWrapper(Module& wasm) {
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std::string ret;
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for (auto& exp : wasm.exports) {
27+
auto* func = wasm.getFunctionOrNull(exp->value);
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if (!func) continue; // something exported other than a function
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ret += std::string("(invoke \"hangLimitInitializer\") (invoke \"") + exp->name.str + "\" ";
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for (WasmType param : func->params) {
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// zeros in arguments TODO more?
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switch (param) {
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case i32: ret += "(i32.const 0)"; break;
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case i64: ret += "(i64.const 0)"; break;
35+
case f32: ret += "(f32.const 0)"; break;
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case f64: ret += "(f64.const 0)"; break;
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default: WASM_UNREACHABLE();
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}
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ret += " ";
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}
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ret += ") ";
42+
}
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return ret;
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}
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} // namespace wasm
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