### Setup MiniReact Benchmark Environment

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/MiniReact/no-objects/README.md

Installs dependencies for the flow-bundler and configures the build environment for the MiniReact benchmark. Ensure you are in the correct directory before running.

```bash
(cd ~/builds; cmake -S ~/fbsource/xplat/static_h/benchmarks/ -B benchmarksdebug -G Ninja -DHERMES_BUILD=~/builds/shdebug -DHERMES_SRC=~/fbsource/xplat/static_h) && (cd ~/fbsource/xplat/static_h/benchmarks/build-helpers/flow-bundler; yarn install)
```

--------------------------------

### Implement C++ Extension Installation

Source: https://github.com/facebook/hermes/blob/static_h/API/hermes/extensions/contrib/README.md

Implement the C++ function to register native helpers and call the JavaScript setup function.

```cpp
/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

#include "YourExtension.h"
#include "../Intrinsics.h"  // If you need intrinsics

namespace facebook {
namespace hermes {

void installYourExtension(jsi::Runtime &rt, jsi::Object &extensions) {
  // Create native helpers object if needed
  jsi::Object nativeHelpers = jsi::Object(rt);

  // Add native functions (optional)
  nativeHelpers.setProperty(rt, "myNativeFunc",
    jsi::Function::createFromHostFunction(rt,
      jsi::PropNameID::forAscii(rt, "myNativeFunc"),
      1,  // argument count
      [](jsi::Runtime &rt, const jsi::Value &, 
         const jsi::Value *args, size_t count) -> jsi::Value {
        // Implementation
        return jsi::Value::undefined();
      }));

  // Get and call the setup function
  jsi::Function setup = extensions.getPropertyAsFunction(rt, "YourExtension");
  setup.call(rt, nativeHelpers);
}

} // namespace hermes
} // namespace facebook

```

--------------------------------

### Install and Run lit via Setuptools

Source: https://github.com/facebook/hermes/blob/static_h/external/llvh/utils/lit/README.txt

Install lit using setuptools and then run the test suite. This verifies that lit functions correctly when installed as a package.

```shell
python utils/lit/setup.py install
lit --path /path/to/your/llvm/build/bin utils/lit/tests
```

--------------------------------

### Install Dependencies and Build ES5 Widgets

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/widgets/original/es5/README.md

Run these commands to install project dependencies and then build the ES5 widgets.js file.

```bash
npm install
npm run build
```

--------------------------------

### Install Hermes executable

Source: https://github.com/facebook/hermes/blob/static_h/tools/hermes/CMakeLists.txt

Installs the 'hermes' executable to the 'bin' directory in the runtime destination.

```cmake
install(TARGETS hermes
  RUNTIME DESTINATION bin
)
```

--------------------------------

### Interact with SQLite Database using sqlite.js

Source: https://github.com/facebook/hermes/blob/static_h/examples/ffi/README.md

Example of using libsqlite3 via FFI to open a database, execute a query, and print results. Requires libsqlite3 installation. Run with 'shermes -typed -exec sqlite.js -lsqlite3'.

```javascript
const sqlite3 = require('sqlite3');

const db = new sqlite3.Database(':memory:');

db.serialize(() => {
  db.run('CREATE TABLE users (id INT, name TEXT)');
  db.run("INSERT INTO users VALUES (1, 'Alice')");
  db.run("INSERT INTO users VALUES (2, 'Bob')");

  db.each('SELECT * FROM users', (err, row) => {
    console.log(row);
  });
});

db.close();

```

--------------------------------

### Install AsmJit Library and Headers

Source: https://github.com/facebook/hermes/blob/static_h/external/asmjit/asmjit/CMakeLists.txt

Configures the installation of the AsmJit library, export files, and public headers. This is skipped if ASMJIT_NO_INSTALL is set.

```cmake
if (NOT ASMJIT_NO_INSTALL)
  install(TARGETS asmjit
          EXPORT asmjit-config
          RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
          ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
          LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
          INCLUDES DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}")
  install(EXPORT asmjit-config
          NAMESPACE asmjit::
          DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/asmjit")

  foreach(_src_file ${ASMJIT_SRC_LIST})
    if ("${_src_file}" MATCHES "\.h$" AND NOT "${_src_file}" MATCHES "_p\.h$")
      get_filename_component (_src_dir ${_src_file} PATH)
      install(FILES "${ASMJIT_DIR}/src/${_src_file}" DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/${_src_dir}")
    endif()
  endforeach()
endif()
```

--------------------------------

### Install Hermes VM Executable

Source: https://github.com/facebook/hermes/blob/static_h/tools/hvm/CMakeLists.txt

Installs the 'hvm' target to the 'bin' directory at runtime.

```cmake
install(TARGETS hvm
  RUNTIME DESTINATION bin
)
```

--------------------------------

### Install babel-plugin-syntax-hermes-parser with npm

Source: https://github.com/facebook/hermes/blob/static_h/tools/hermes-parser/js/babel-plugin-syntax-hermes-parser/README.md

Install the plugin as a development dependency using npm.

```sh
npm install --save-dev babel-plugin-syntax-hermes-parser
```

--------------------------------

### Install npm packages for hcdp

Source: https://github.com/facebook/hermes/blob/static_h/tools/hcdp/README.md

Run this command to install the necessary npm packages before executing the hcdp tool.

```bash
npm install
```

--------------------------------

### Install babel-plugin-syntax-hermes-parser with yarn

Source: https://github.com/facebook/hermes/blob/static_h/tools/hermes-parser/js/babel-plugin-syntax-hermes-parser/README.md

Install the plugin as a development dependency using yarn.

```sh
yarn add babel-plugin-syntax-hermes-parser --dev
```

--------------------------------

### Install and Run Tests

Source: https://github.com/facebook/hermes/blob/static_h/tools/hermes-parser/js/CLAUDE.md

Install project dependencies and run Jest tests. Supports running tests with an optional pattern.

```bash
yarn install   # first time only
yarn test [<pattern>]
```

--------------------------------

### Context Notes Example for a Step

Source: https://github.com/facebook/hermes/blob/static_h/doc/plans/ir-type/progress.md

Provides an example of the format for context notes after a step is completed or blocked. It includes sections for files, decisions, actions taken, issues encountered, and notes for the next step.

```markdown
### Step 11: Port util binding
- **Files**: created `foo.c`, modified `bar.c`.
- **Decisions**:
-- Decision 1 concise explanation
-- Decision 2 concise explanation
- **What was done**: ...
- **Issues**: ...
- **Notes for next step**: ...
```

--------------------------------

### Installing TypeContextRAII at Module Creation

Source: https://github.com/facebook/hermes/blob/static_h/doc/plans/ir-type/ir-type-v2-implementation.md

Demonstrates how to install the TypeContextRAII guard at the beginning of a module's lifetime to cover all subsequent Type operations.

```cpp
// At Module creation:
TypeContextRAII guard(module->getTypeContext());
// All Type operations for the lifetime of the Module are now covered.
```

--------------------------------

### Setting up ARM32 Execution on ARM64 Linux

Source: https://github.com/facebook/hermes/blob/static_h/doc/CrossCompilation.md

Install necessary libraries for running ARM32 binaries on an ARM64 Linux host.

```bash
# Add architecture
dpkg --add-architecture armhf
# Update
sudo apt update
# For running
sudo apt install libc6:armhf libstdc++6:armhf
```

--------------------------------

### Install npm Dependencies

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/build-helpers/flow-bundler/README.md

Install the necessary npm dependencies before using the Flow Bundler. Use either yarn or npm for installation.

```bash
yarn install
```

```bash
npm install
```

--------------------------------

### Install Hermes CDP Tool

Source: https://github.com/facebook/hermes/blob/static_h/tools/hcdp/CMakeLists.txt

Installs the hcdp tool executable to the bin directory.

```cmake
install(TARGETS hcdp
  RUNTIME DESTINATION bin
)
```

--------------------------------

### Start Fuzzing

Source: https://github.com/facebook/hermes/blob/static_h/tools/fuzzers/fuzzilli/README.md

Execute Fuzzilli with the Hermes profile, pointing to the location of the built binary. Ensure $BINARY_LOCATION is correctly set.

```shell
cd $FUZZILLI_LOCATION
swift run  FuzzilliCli --profile=hermes $BINARY_LOCATION
```

--------------------------------

### Hermes ESLint Parser Options Example

Source: https://github.com/facebook/hermes/blob/static_h/tools/hermes-parser/js/hermes-eslint/README.md

Example of providing parser options for hermes-eslint in a legacy ESLint configuration.

```json
{
  "parser": "hermes-eslint",
  "parserOptions": {
    "sourceType": "module"
  }
}
```

--------------------------------

### Setting up ARM32 Compilation on ARM64 Linux

Source: https://github.com/facebook/hermes/blob/static_h/doc/CrossCompilation.md

Install necessary packages for compiling ARM32 binaries on an ARM64 Linux host, including C/C++ compilers and libraries.

```bash
# Add architecture
dpkg --add-architecture armhf
# Update
sudo apt update
# For compiling
sudo apt install gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf binutils-arm-linux-gnueabihf libc6:armhf libstdc++6:armhf
```

--------------------------------

### Install and Activate Emscripten Toolchain

Source: https://github.com/facebook/hermes/blob/static_h/doc/Emscripten.md

Installs the latest Emscripten SDK and activates it for use. Ensure you are in the directory where you downloaded emsdk.

```shell
./emsdk install latest
./emsdk activate latest
```

--------------------------------

### Benchmark Results Output

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/bench-runner/README.md

Example output from the bench-runner script, showing benchmark names and their total execution times.

```text
Ran each benchmark 1 times
Runtime:  hermes
General Stats:
                   Benchmark                       total
                                                  (time)
--------------------------------------------------------
                   v8-crypto           552.0  s +-  0.0%
                v8-deltablue           787.0  s +-  0.0%
                 v8-raytrace           163.0  s +-  0.0%
                   v8-regexp           329.0  s +-  0.0%
                 v8-richards           854.0  s +-  0.0%
                    v8-splay           139.0  s +-  0.0%
```

--------------------------------

### Install Hermes Debugger Tool

Source: https://github.com/facebook/hermes/blob/static_h/tools/hdb/CMakeLists.txt

Install the 'hdb' target to the 'bin' directory at runtime.

```cmake
install(TARGETS hdb
  RUNTIME DESTINATION bin
)
```

--------------------------------

### Install Dependencies with Yarn

Source: https://github.com/facebook/hermes/blob/static_h/API/hermes/cdp/tools/hermes-inspector-msggen/README.md

Installs the necessary development dependencies for the hermes-inspector-msggen package. This command should be run as a dev dependency.

```bash
yarn add --dev @babel/cli @babel/core @babel/preset-env @babel/preset-flow jest @react-native/hermes-inspector-msggen
```

--------------------------------

### Type Interning Example

Source: https://github.com/facebook/hermes/blob/static_h/doc/plans/ir-type/ir-type-v2-implementation.md

Demonstrates the interning process for creating an array type, showing how existing types are reused via a hash table lookup.

```cpp
createArray(elemType):
  key = {kind: Array, elemType.id_}
  if internTable_.count(key):
    return Type(internTable_[key])
  id = entries_.size()
  entries_.push_back({TypeKind::Array, {.array = {elemType}}})
  internTable_[key] = id
  return Type(id)
```

--------------------------------

### Configuration Struct Fields

Source: https://github.com/facebook/hermes/blob/static_h/public/hermes/Public/README.md

Example of fields generated for a configuration struct, including their types, names, and default values.

```cpp
size_t Bar_ = 0;
std::string Baz_ = "Hello";
```

--------------------------------

### Install Hermes Public Header Files

Source: https://github.com/facebook/hermes/blob/static_h/public/hermes/Public/CMakeLists.txt

Installs the header files for the Hermes public library to the include directory. This ensures the library's headers are accessible.

```cmake
install(DIRECTORY "${PROJECT_SOURCE_DIR}/public/hermes/Public" DESTINATION include/hermes
  FILES_MATCHING PATTERN "*.h")
install(DIRECTORY "${HERMES_COMMON_DIR}/public/hermes/Public" DESTINATION include/hermes
  FILES_MATCHING PATTERN "*.h")
```

--------------------------------

### Run JavaScript with Hermes CLI

Source: https://github.com/facebook/hermes/blob/static_h/README.md

Example of executing a simple JavaScript snippet using the built Hermes CLI. The script prints 'Hello World'.

```shell
echo "'use strict'; function hello() { print('Hello World'); } hello();" | ./bin/hermes
```

--------------------------------

### Shermes Execution Command

Source: https://github.com/facebook/hermes/blob/static_h/tools/test-runner/DESIGN.md

Example of the command used to run compiled bytecode with Shermes.

```bash
<binary> -Xes6-proxy -Xhermes-internal-test-methods -Xmicrotask-queue
```

--------------------------------

### Require Module Example

Source: https://github.com/facebook/hermes/blob/static_h/doc/Modules.md

Demonstrates how to require another module using the 'require' function provided by the Hermes runtime. The argument must be an absolute path relative to the ZIP file or input directory root.

```javascript
const Foo = require('/subdir/foo.js');

Foo.doSmth();
```

--------------------------------

### Register Extension in ContribExtensions.cpp

Source: https://github.com/facebook/hermes/blob/static_h/API/hermes/extensions/contrib/README.md

Include your extension's header and call its installation function within the `installContribExtensions` function.

```cpp
#include "ContribExtensions.h"

#include "ContribDummy.h"
#include "YourExtension.h"  // Add this

void installContribExtensions(jsi::Runtime &rt, jsi::Object &extensions) {
  installContribDummy(rt, extensions);
  installYourExtension(rt, extensions);  // Add this
}

```

--------------------------------

### Setup Profiles for Hermes

Source: https://github.com/facebook/hermes/blob/static_h/tools/fuzzers/fuzzilli/README.md

Move the Swift profile files into the Fuzzilli Sources directory. Ensure the FUZZILLI_LOCATION environment variable is set correctly.

```shell
mv profile/*.swift $FUZZILLI_LOCATION/Sources/FuzzilliCli/Profiles/
```

--------------------------------

### Example Metadata JSON File

Source: https://github.com/facebook/hermes/blob/static_h/doc/Modules.md

This JSON file defines module segments and their resolutions. Segment '0' is the main segment loaded on startup. The resolutionTable maps require() arguments to actual file paths.

```json
{
  "segments": {
    "0": [
      "./cjs-subdir-main.js",
      "cjs-subdir-2.js",
      "bar/cjs-subdir-bar.js",
      "foo/cjs-subdir-foo.js"
    ]
  },
  "resolutionTable": {
    "./cjs-subdir-main.js": {
      "foo": "./foo/cjs-subdir-foo.js"
    },
    "./foo/cjs-subdir-foo.js": {
      "bar": "./bar/cjs-subdir-bar.js"
    }
  }
}
```

--------------------------------

### Deep Profiling Workflow

Source: https://github.com/facebook/hermes/blob/static_h/agent-perf/README.md

A five-step workflow for deep performance profiling, starting from PMU counters and ending with source-level hotspot annotation.

```bash
# Step 1: Collect PMU counters
agent-perf/tools/collect_pmu.sh <shermes> workload.js --json > /tmp/pmu.json
```

```bash
# Step 2: Check for anomalies
agent-perf/tools/pmu_anomalies.py -i /tmp/pmu.json
```

```bash
# Step 3: Profile with perf
perf record -g -- ./compiled_binary
perf report --stdio > /tmp/report.txt
```

```bash
# Step 4: Parse profile and find hot runtime functions
agent-perf/tools/profile_to_json.py -i /tmp/report.txt --json
agent-perf/tools/runtime_call_profiler.py -i /tmp/report.txt --json
```

```bash
# Step 5: Annotate source with hotspots
perf annotate --stdio > /tmp/annotate.txt
agent-perf/tools/annotate_source.py -i /tmp/annotate.txt
```

--------------------------------

### Run Richards Benchmark Simulation

Source: https://github.com/facebook/hermes/blob/static_h/test/AST2JS/richards.js.txt

Initializes and runs the Richards benchmark simulation. It sets up various tasks (idle, worker, handler, device) and their queues, then starts the scheduler. Includes error checking for expected queue and hold counts.

```javascript
function runRichards() {
  var scheduler = new Scheduler();
  scheduler.addIdleTask(ID_IDLE, 0, null, COUNT);

  var queue = new Packet(null, ID_WORKER, KIND_WORK);
  queue = new Packet(queue,  ID_WORKER, KIND_WORK);
  scheduler.addWorkerTask(ID_WORKER, 1000, queue);

  queue = new Packet(null, ID_DEVICE_A, KIND_DEVICE);
  queue = new Packet(queue,  ID_DEVICE_A, KIND_DEVICE);
  queue = new Packet(queue,  ID_DEVICE_A, KIND_DEVICE);
  scheduler.addHandlerTask(ID_HANDLER_A, 2000, queue);

  queue = new Packet(null, ID_DEVICE_B, KIND_DEVICE);
  queue = new Packet(queue,  ID_DEVICE_B, KIND_DEVICE);
  queue = new Packet(queue,  ID_DEVICE_B, KIND_DEVICE);
  scheduler.addHandlerTask(ID_HANDLER_B, 3000, queue);

  scheduler.addDeviceTask(ID_DEVICE_A, 4000, null);

  scheduler.addDeviceTask(ID_DEVICE_B, 5000, null);

  scheduler.schedule();

  if (scheduler.queueCount != EXPECTED_QUEUE_COUNT ||
      scheduler.holdCount != EXPECTED_HOLD_COUNT) {
    var msg =
        "Error during execution: queueCount = " + scheduler.queueCount +
        ", holdCount = " + scheduler.holdCount + ".";
    throw new Error(msg);
  }
}
```

--------------------------------

### Real-world example: Array constructor

Source: https://github.com/facebook/hermes/blob/static_h/doc/GCSafeCoding.md

Illustrates the use of PinnedValue for managing 'self' and 'selfParent' within the array constructor function.

```cpp
CallResult<HermesValue> arrayConstructor(void *, Runtime &runtime) {
  NativeArgs args = runtime.getCurrentFrame().getNativeArgs();
  struct : public Locals {
    PinnedValue<JSObject> selfParent;
    PinnedValue<JSArray> self;
  } lv;
  LocalsRAII lraii(runtime, &lv);

  if (LLVM_LIKELY(!args.isConstructorCall() || ...)) {
    CallResult<PseudoHandle<JSArray>> selfRes = 
        JSArray::create(runtime, runtime.arrayPrototype);
    if (LLVM_UNLIKELY(selfRes == ExecutionStatus::EXCEPTION))
      return ExecutionStatus::EXCEPTION;
    lv.self = std::move(*selfRes);
  } else {
    CallResult<PseudoHandle<JSObject>> thisParentRes = 
        NativeConstructor::parentForNewThis_RJS(runtime, ...);
    if (LLVM_UNLIKELY(thisParentRes == ExecutionStatus::EXCEPTION))
      return ExecutionStatus::EXCEPTION;
    lv.selfParent = std::move(*thisParentRes);
    auto arrRes = JSArray::create(runtime, lv.selfParent);
    if (LLVM_UNLIKELY(arrRes == ExecutionStatus::EXCEPTION))
      return ExecutionStatus::EXCEPTION;
    lv.self = std::move(*arrRes);
  }

  // ...use lv.self throughout the rest of the function...
  return lv.self.getHermesValue();
}
```

--------------------------------

### BranchInst Example

Source: https://github.com/facebook/hermes/blob/static_h/doc/IR.md

Represents a jump to a different basic block. Terminates the current basic block and transfers control. Does not interact with memory.

```hermes-ir
%0 = BranchInst %BB1
```

--------------------------------

### JS Setup for TextEncoder JSI Extension

Source: https://github.com/facebook/hermes/blob/static_h/doc/blog/2025-12-12-new-way-to-contribute.md

This JavaScript code sets up the TextEncoder constructor and its prototype methods, receiving native C++ implementations as arguments. It's designed to be called from C++ and installs the TextEncoder on the globalThis object.

```javascript
extensions.TextEncoder = function(nativeInit, nativeEncode, nativeEncodeInto) {
  function TextEncoder() {
    if (!new.target) {
      throw new TypeError('TextEncoder must be called as a constructor');
    }
    nativeInit(this);
  }

  TextEncoder.prototype.encode = nativeEncode;
  TextEncoder.prototype.encodeInto = nativeEncodeInto;

  // ... property definitions ...

  globalThis.TextEncoder = TextEncoder;
};
```

--------------------------------

### Merged Benchmark Comparison Output

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/bench-runner/README.md

Example output from bench-merge, showing a comparison of benchmark results between two different runs (e.g., 'before' and 'after' revisions of Hermes). Includes total time and ratio.

```text
                      runner                   benchmark                  Total time                       ratio
================================================================================================================
             hermes (before)                       box2d          1677.4  s +-  0.8%                       1.000
              hermes (after)                       box2d          1653.4  s +-  0.3%                       0.986
----------------------------------------------------------------------------------------------------------------
             hermes (before)                   code-load          2376.0  s +-  1.5%                       1.000
              hermes (after)                   code-load          2433.0  s +-  4.8%                       1.024
...
             hermes (before)                    v8-splay           115.4  s +-  0.8%                       1.000
              hermes (after)                    v8-splay           113.8  s +-  1.7%                       0.986
----------------------------------------------------------------------------------------------------------------
             hermes (before)                     geomean                                                   1.000
              hermes (after)                     geomean                                                   0.988
```

--------------------------------

### Configure AsmJit Target Options

Source: https://github.com/facebook/hermes/blob/static_h/external/asmjit/asmjit/CMakeLists.txt

Sets compile options and include directories for the AsmJit target. Ensures public headers are available for installation and build interfaces.

```cmake
target_compile_options(asmjit INTERFACE ${ASMJIT_CFLAGS})
target_include_directories(asmjit BEFORE INTERFACE
                           $<BUILD_INTERFACE:${ASMJIT_INCLUDE_DIRS}>
                           $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
```

--------------------------------

### Dependency Graph for Phase 1

Source: https://github.com/facebook/hermes/blob/static_h/doc/plans/ir-type/phase1-steps.md

Visualizes the dependencies between different implementation steps in Phase 1. This graph guides the order of commits to ensure all prerequisites are met.

```text
P1-S1 (skeleton)
 ├──→ P1-S2 (queries) ──→ P1-S3 (operations) ──→ P1-S4 (utilities)
 ├──→ P1-S5 (thread-local)
 └──→ P1-S6 (wire into Module)
                    P1-S5 + P1-S6 ──→ P1-S7 (RAII at entry points)
                           P1-S7 ──→ P1-S7.5 (RAII in tests)
                    P1-S4 + P1-S7.5 ──→ P1-S8 (rewrite Type)

```

--------------------------------

### Flow Bundler Help Command

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/build-helpers/flow-bundler/README.md

View detailed usage instructions and available options for the Flow Bundler by running the help command.

```bash
./benchmarks/build-helpers/flow-bundler/bin/flow-bundler --help
```

--------------------------------

### Create a JavaScript File

Source: https://github.com/facebook/hermes/blob/static_h/doc/Emscripten.md

Creates a simple JavaScript file named 'hello.js' with a console log statement. This file will be used to test the Wasm Hermes VM.

```shell
echo 'var x = "hello"; console.log(`${x} world`);' > hello.js
```

--------------------------------

### Basic Flow Bundler Usage

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/build-helpers/flow-bundler/README.md

Execute the Flow Bundler with essential arguments: output path, project root, and entry point files. This command generates a single bundle file.

```bash
./benchmarks/build-helpers/flow-bundler/bin/flow-bundler \
  --out output/path/of/bundle.js
  --root project/root
  path/to/entrypoint1.js
  path/to/entrypoint2.js
```

--------------------------------

### Create Class Instance

Source: https://github.com/facebook/hermes/blob/static_h/doc/IR.md

Constructs a new class from its constructor code. %function is the constructor code, %scope is the environment, %varScope describes %scope, %superClass is the parent class, and %homeObjectOutput receives the class's prototype.

```hermes-ir
%0 = CreateClassInst %scope, %varScope, %function, %superClass, %homeObjectOutput
```

--------------------------------

### ResolveScopeInst

Source: https://github.com/facebook/hermes/blob/static_h/doc/IR.md

Traverses the scope chain to retrieve an enclosing scope. It requires the target VariableScope, the starting scope, and the VariableScope associated with the starting scope. The target scope must be reachable from the starting scope. This instruction does not interact with memory.

```APIDOC
## ResolveScopeInst

### Description
Traverse the scope chain to retrieve an enclosing scope.

### Semantics
The instruction retrieves the requested scope, which must be reachable from the starting scope.

### Arguments
- **%variablescope** (VariableScope) - The VariableScope corresponding to the enclosing scope to retrieve.
- **%startVarScope** (VariableScope) - The VariableScope associated with %startScope.
- **%startScope** (scope) - The scope from which to start traversing.

### Example
`%0 = ResolveScopeInst %variablescope, %startVarScope, %startScope`

### Effects
Does not read or write to memory.
```

--------------------------------

### Install JSI Header Files

Source: https://github.com/facebook/hermes/blob/static_h/API/jsi/jsi/CMakeLists.txt

Installs JSI header files to the include directory, excluding test files.

```cmake
install(DIRECTORY "${PROJECT_SOURCE_DIR}/API/jsi/" DESTINATION include
  FILES_MATCHING PATTERN "*.h"
  PATTERN "test" EXCLUDE)
```

--------------------------------

### Clone and Copy LIT Utilities

Source: https://github.com/facebook/hermes/blob/static_h/external/llvh/README.md

This command sequence demonstrates how to obtain updated LIT testing tool utilities from the LLVM project repository. It involves cloning the LLVM project, checking out a specific commit, and copying the relevant LIT utility files to the Hermes project's external directory.

```bash
git clone https://github.com/llvm/llvm-project.git
cd llvm-project
git checkout c1a0a213378a458fbea1a5c77b315c7dce08fd05
cp -r ./llvm/utils/lit/* /path/to/hermes/external/llvh/utils/lit
```

--------------------------------

### Build Instrumented Binary

Source: https://github.com/facebook/hermes/blob/static_h/tools/fuzzers/fuzzilli/README.md

Configure and build the instrumented binary using CMake with Fuzzilli and trace PC guard enabled. Ensure $OTHER_FLAGS are set if needed.

```shell
mkdir fuzzilli_build && cd fuzzilli_build
cmake .. -DHERMES_ENABLE_FUZZILLI=ON -DHERMES_ENABLE_TRACE_PC_GUARD=ON $OTHER_FLAGS
make fuzzilli
```

--------------------------------

### File Operations with fopen.js

Source: https://github.com/facebook/hermes/blob/static_h/examples/ffi/README.md

Demonstrates basic file operations like opening, reading, and closing files using FFI. Run with 'shermes -typed -exec fopen.js'.

```javascript
const fs = require('fs');

const fd = fs.open('test.txt', 'w');
fs.write(fd, 'Hello from Hermes FFI!\n');
fs.close(fd);

const content = fs.read('test.txt');
console.log(content);

```

--------------------------------

### Example Hermes IR Function

Source: https://github.com/facebook/hermes/blob/static_h/doc/IR.md

A well-formed example of a function in Hermes IR, demonstrating basic blocks and control flow instructions like BranchInst, CondBranchInst, and ReturnInst.

```hermesir
function forEach(cond : boolean, value : number)
  %BB0:
    %0 = BranchInst %BB1
  %BB1:
    %2 = CondBranchInst %cond, %BB2, %BB3
  %BB2:
    %3 = ReturnInst %cond
  %BB3:
    %4 = ReturnInst %value
```

--------------------------------

### Union Type Examples

Source: https://github.com/facebook/hermes/blob/static_h/doc/plans/ir-type/ir-type-system-v2-design.md

Illustrates the syntax for defining union types, which represent values that can be one of several member types. These examples show unions of primitives, classes, and null.

```hermesir
Union(Number, String)          -- number or string
Union(ClassA, ClassB)          -- instance of ClassA or ClassB
Union(Number, ClassA, Null)    -- number, ClassA instance, or null
```

--------------------------------

### Add Executable and Link Libraries

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/imgui-demo/CMakeLists.txt

Defines the main executable for the ImGui demo and links it against the 'gui' library.

```cmake
add_executable(imdemo-cpp imdemo-cpp.cpp ${BLOBS})
target_link_libraries(imdemo-cpp gui)
```

--------------------------------

### Install iOS Pods with Custom Hermes Build

Source: https://github.com/facebook/hermes/blob/static_h/doc/ReactNativeIntegration.md

After disabling the default Hermes pod, run this command to install pods and enable building from source for your custom Hermes integration on iOS.

```bash
BUILD_FROM_SOURCE=true bundle exec pod install
```

--------------------------------

### Get Fuzzilli

Source: https://github.com/facebook/hermes/blob/static_h/tools/fuzzers/fuzzilli/README.md

Clone the Fuzzilli repository to your local machine.

```shell
git clone https://github.com/googleprojectzero/fuzzilli.git
```

--------------------------------

### Instance Data

Source: https://github.com/facebook/hermes/blob/static_h/API/napi/COMPATIBILITY.md

Functions for setting and getting instance data.

```APIDOC
## Instance Data

### Description
Functions for setting and getting instance data.

### Functions
- `napi_set_instance_data`
- `napi_get_instance_data`
```

--------------------------------

### Profile JIT-Compiled Code with Perf

Source: https://github.com/facebook/hermes/blob/static_h/doc/PerfProfiling.md

Use this command sequence to record, inject, and report JIT performance traces. Ensure you have a Linux machine with ARM64 architecture. The flags `-Xperf-prof` and `-Xperf-prof-dir` enable and specify the output directory for perf profiling, respectively. `-k mono` uses CLOCK_MONOTONIC for clock ID, matching jitdump. Sampling is set to user-space events by default.

```bash
perf record -g -k mono -e cycles:u ./bin/hermes ~/js/test.js -Xjit=force \
  -Xperf-prof -Xperf-prof-dir ./
perf inject -j -i perf.data -o perf.data.jitted
perf report -i perf.data.jitted --call-graph=fractal,callee --children
```

--------------------------------

### Get Builtin Closure

Source: https://github.com/facebook/hermes/blob/static_h/doc/IR.md

Retrieves a closure for a specified builtin function. Reads from memory.

```hermesir
%0 = GetBuiltinClosureInst %builtinNumber
```

--------------------------------

### Create C++ Header for Extension

Source: https://github.com/facebook/hermes/blob/static_h/API/hermes/extensions/contrib/README.md

Declare the C++ function that will install your extension into the Hermes runtime.

```cpp
/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

#ifndef HERMES_EXTENSIONS_CONTRIB_YOUREXTENSION_H
#define HERMES_EXTENSIONS_CONTRIB_YOUREXTENSION_H

#include <jsi/jsi.h>

namespace facebook {
namespace hermes {

void installYourExtension(jsi::Runtime &runtime, jsi::Object &extensions);

} // namespace hermes
} // namespace facebook

#endif

```

--------------------------------

### Configuration Accessors

Source: https://github.com/facebook/hermes/blob/static_h/public/hermes/Public/README.md

Example of getter methods generated for accessing fields within a configuration struct.

```cpp
size_t FooConfig::getBar() const;
std::string FooConfig::getBaz() const;
```

--------------------------------

### Read from PinnedValue

Source: https://github.com/facebook/hermes/blob/static_h/doc/GCSafeCoding.md

Access the underlying typed value, dereference for member access, or get as a HermesValue.

```cpp
// Get the underlying typed value:
JSObject *rawPtr = lv.obj.get();   // or *lv.obj
JSObject *rawPtr = *lv.obj;

// Dereference to access members:
lv.obj->someMethod();

// Get as HermesValue:
HermesValue hv = lv.obj.getHermesValue();
```

--------------------------------

### Shermes Compilation Command

Source: https://github.com/facebook/hermes/blob/static_h/tools/test-runner/DESIGN.md

Example of the command used for compiling source code with the Shermes AOT compiler.

```bash
shermes <source> -o <binary> <COMPILE_ARGS> [-strict] [-O|-O0]
```

--------------------------------

### Run MiniReact Benchmark with Static Hermes

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/MiniReact/no-objects/README.md

Builds and runs the MiniReact benchmark using Static Hermes. This command compiles the benchmark and then executes it with the Static Hermes interpreter.

```bash
~/fbsource/xplat/static_h/benchmarks/MiniReact/no-objects/build.sh && (cd ~/builds/shdebug/; ninja hermesvm shermes && ./bin/shermes -typed -exec -g ~/fbsource/xplat/static_h/benchmarks/MiniReact/no-objects/out/simple.js)
```

--------------------------------

### Hermes VM Flags

Source: https://github.com/facebook/hermes/blob/static_h/utils/testsuite/README.md

Example VM flags for running the test262 and CVE test suites with Hermes.

```sh
# For hermes VM (running the bytecode)
-Xes6-proxy -Xhermes-internal-test-methods -Xmicrotask-queue
```

--------------------------------

### Build and Run NAPI Unit Tests

Source: https://github.com/facebook/hermes/blob/static_h/API/napi/README.md

Compile and execute the NAPI unit tests. This command assumes your build directory is set up correctly.

```bash
cmake --build <build-dir> --target NapiTests && <build-dir>/unittests/napi/NapiTests
```

--------------------------------

### Compile and Execute JavaScript Bytecode with Wasm Hermes VM

Source: https://github.com/facebook/hermes/blob/static_h/doc/Emscripten.md

Compiles 'hello.js' to Hermes bytecode ('hello.hbc') and then executes the bytecode using the Wasm Hermes VM. This shows the two-step execution process.

```shell
node ./build-wasm/bin/hermes.js hello.js --emit-binary -out hello.hbc
node ./build-wasm/bin/hermes.js hello.hbc
```

--------------------------------

### Hermes Compiler Flags

Source: https://github.com/facebook/hermes/blob/static_h/utils/testsuite/README.md

Example compiler flags for running the test262 and CVE test suites with Hermes.

```sh
# For hermes compiler
-test262 -fno-static-builtins -Xes6-block-scoping -Xenable-tdz
```

--------------------------------

### TypeContext Constructor Initialization

Source: https://github.com/facebook/hermes/blob/static_h/doc/plans/ir-type/ir-type-v2-implementation.md

Shows the initial pre-allocation of well-known types within the TypeContext constructor, starting with NoType.

```cpp
TypeContext::TypeContext() {
  // Index 0: NoType
  entries_.push_back({TypeKind::NoType, {}});
  // Index 1: Empty
  entries_.push_back({TypeKind::Empty, {}});
  // Index 2: Uninit
  entries_.push_back({TypeKind::Uninit, {}});
  // ... all primitives and well-known unions ...
  // Index kAnyTypeId: Union of all JS-observable types
  // Index kNumericId: Union(Number, BigInt)
  // ...
  assert(entries_.size() == kFirstDynamicId);
}
```

--------------------------------

### Run MiniReact Benchmark with Hermes

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/MiniReact/no-objects/README.md

Builds and runs the MiniReact benchmark using standard Hermes. This command compiles the benchmark and then executes it with the standard Hermes interpreter.

```bash
~/fbsource/xplat/static_h/benchmarks/MiniReact/no-objects/build.sh && (cd ~/builds/shdebug/; ninja hermesvm hermes && ./bin/hermes -exec -g ~/fbsource/xplat/static_h/benchmarks/MiniReact/no-objects/out/simple-lowered.js)
```

--------------------------------

### HBCResolveParentEnvironmentInst

Source: https://github.com/facebook/hermes/blob/static_h/doc/IR.md

Traverses the chain of lexical environments starting from the current function's parent to find a specific environment.

```APIDOC
## HBCResolveParentEnvironmentInst

### Description
Traverse the chain of environments starting at the current function's parent to find a given environment.

### Example
```
%0 = HBCResolveParentEnvironmentInst %varScope, %numLevels, %parentScopeParam
```

### Arguments
- **%varScope**: The variable scope to resolve to.
- **%numLevels**: The number of scopes up from the current function's parent that the result will be found.
- **%parentScopeParam**: Dummy parameter used to model usage of the parent environment.

### Semantics
The instruction resolves an environment that is a parent of the current function's environment.

### Effects
Does not read or write to memory.
```

--------------------------------

### Create JavaScript Extension File

Source: https://github.com/facebook/hermes/blob/static_h/API/hermes/extensions/contrib/README.md

Define the JavaScript entry point for your extension. This function is called by Hermes and receives native helpers.

```javascript
/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

// YourExtension description
  extensions.YourExtension = function(nativeHelpers) {
    // Setup code here
    // nativeHelpers contains any native functions passed from C++
  };

```

--------------------------------

### Build and Run Hermes Benchmarks

Source: https://github.com/facebook/hermes/blob/static_h/agent-perf/README.md

Build the shermes binary using cmake and then run micro benchmarks with the `--json` flag for structured output. This is useful for initial performance checks.

```bash
cmake -B cmake-build-release -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build cmake-build-release --target shermes
```

```bash
agent-perf/tools/run_benchmarks.sh <shermes> micro --json
```

--------------------------------

### Run LLVM-lit Wrapper Script

Source: https://github.com/facebook/hermes/blob/static_h/external/llvh/utils/lit/README.txt

Execute the llvm-lit wrapper script to test LLVM. This command is used after building LLVM tools to ensure proper integration.

```shell
/path/to/your/llvm/build/bin/llvm-lit utils/lit/tests
```

--------------------------------

### Locals and loops with GCScope

Source: https://github.com/facebook/hermes/blob/static_h/doc/GCSafeCoding.md

Demonstrates using Locals for long-lived values and GCScope for short-lived temporaries within a loop, flushing temporaries each iteration.

```cpp
struct : Locals {
  PinnedValue<JSObject> O;
  PinnedValue<> elem;
  PinnedValue<StringPrimitive> sep;
} lv;
LocalsRAII lraii(runtime, &lv);

GCScope gcScope(runtime);
// ...
auto marker = gcScope.createMarker();
for (uint32_t i = 0; i < len; gcScope.flushToMarker(marker), ++i) {
  // Temporary handles created inside the loop are flushed each iteration.
  // Long-lived values stored in lv.* persist across iterations.
  auto strRes = toString_RJS(runtime, lv.elem);
  if (LLVM_UNLIKELY(strRes == ExecutionStatus::EXCEPTION))
    return ExecutionStatus::EXCEPTION;
  lv.sep = std::move(*strRes);
}
```

--------------------------------

### TypeOfInst: Get Value Type

Source: https://github.com/facebook/hermes/blob/static_h/doc/IR.md

Implements the JavaScript `typeof` operator. Returns a string representing the type of the given value.

```hermes-ir
%0 = TypeOfInst %val
```

--------------------------------

### List Functions in C++ File

Source: https://github.com/facebook/hermes/blob/static_h/CLAUDE.md

Lists all functions in a C++ file, sorted by line number. Requires the 'ctags' utility to be installed.

```bash
utils/dump-cpp-funcs.sh file.cpp
```

--------------------------------

### Run Micro-benchmark with Host and Wasm Hermes VMs

Source: https://github.com/facebook/hermes/blob/static_h/doc/Emscripten.md

Compares the performance of the Wasm Hermes VM against the native host VM by running a JavaScript micro-benchmark. This helps in performance analysis.

```shell
# Run the micro-benchmark with the host VM.
./build-host/bin/hermes -w ${HermesSourcePath?}/benchmarks/bench-runner/resource/test-suites/micros/interp-dispatch.js
# Run it with the Wasm VM
node ./build-wasm/bin/hermes.js -w ${HermesSourcePath?}/benchmarks/bench-runner/resource/test-suites/micros/interp-dispatch.js
```

--------------------------------

### Build Prettier Plugin

Source: https://github.com/facebook/hermes/blob/static_h/tools/hermes-parser/js/prettier-plugin-hermes-parser/CONTRIBUTION.md

Run this script to build the Prettier plugin after making modifications.

```bash
hermes-parser/js$ ./scripts/build-prettier.sh
```

--------------------------------

### LIRResolveScopeInst: Resolve Scope by Levels

Source: https://github.com/facebook/hermes/blob/static_h/doc/IR.md

Traverses the scope chain upwards by a specified number of levels from a starting scope. Does not interact with memory.

```hermes-ir
%0 = LIRResolveScopeInst %variablescope, %startScope, %numLevels
```

--------------------------------

### Assembly: Double to Integer Conversion and Bitwise AND

Source: https://github.com/facebook/hermes/blob/static_h/benchmarks/octane/richards-typed/optimization-notes.md

Demonstrates the assembly process for converting NaN-boxed doubles to integers for bitwise operations and back. This round-trip incurs overhead.

```asm
fjcvtzs  w8, d0       ; double → int32
fjcvtzs  w9, d1       ; double → int32
and      w8, w9, w8   ; actual AND
scvtf    d0, w8       ; int32 → double
```

--------------------------------

### Build Configuration with Builder Pattern

Source: https://github.com/facebook/hermes/blob/static_h/public/hermes/Public/README.md

Use the generated Builder type to create a configuration instance, overriding default values using with methods.

```cpp
auto fooConfig = 
  FooConfig::Builder()
    .withBar(10)
    .withBaz("Hello, world!")
    .build();
```

--------------------------------

### GetTemplateObjectInst: Get Template Object

Source: https://github.com/facebook/hermes/blob/static_h/doc/IR.md

Retrieves a template object from the cache or creates a new one if not found. Used for tagged template functions.

```hermes-ir
%0 = GetTemplateObjectInst %templateObjID, %dup, %string1, ...
```

--------------------------------

### Configure Release Build

Source: https://github.com/facebook/hermes/blob/static_h/CLAUDE.md

Configures a Release build for production, optimized for performance.

```bash
cmake -B cmake-build-release -G Ninja -DCMAKE_BUILD_TYPE=Release
```