Code Instrumentation Generator

Code Instrumentation Generator

Automatically instrument source code to collect runtime information while preserving program semantics.

Workflow

Follow these steps to instrument code:

1. Analyze the Source Code

Understand the code structure and identify instrumentation points:

• Language detection: Identify the programming language
• Code structure: Parse functions, classes, branches, loops
• Entry/exit points: Locate function boundaries
• Control flow: Identify branches (if/else, switch, loops)
• Variable scope: Understand variable declarations and usage

2. Determine Instrumentation Strategy

Choose appropriate instrumentation based on requirements:

Instrumentation levels:

• Function-level: Entry/exit of functions with parameters and return values
• Branch-level: Execution of conditional branches (if/else, switch cases)
• Statement-level: Individual statement execution
• Variable-level: Variable assignments and value changes

Configuration options:

• Enable/disable specific instrumentation types
• Filter by function names or file patterns
• Set verbosity level
• Choose output format (logs, JSON, CSV)

3. Insert Instrumentation Code

Add instrumentation hooks at identified points:

Function instrumentation:

• Insert entry hook at function start
• Capture function name, parameters, timestamp
• Insert exit hook before returns
• Capture return value, execution time

Branch instrumentation:

• Insert hooks at branch conditions
• Record which branch was taken
• Track branch coverage

Variable instrumentation:

• Insert hooks after variable assignments
• Capture variable name and value
• Track value changes over time

4. Ensure Semantic Preservation

Verify that instrumentation doesn't change program behavior:

• No side effects: Instrumentation code doesn't modify program state
• Exception safety: Instrumentation handles exceptions properly
• Performance: Minimal overhead added
• Thread safety: Instrumentation is safe in concurrent code

5. Generate Output

Provide instrumented code and documentation:

• Instrumented source code: Modified code with instrumentation
• Probe description: Documentation of inserted instrumentation points
• Configuration file: Settings to enable/disable instrumentation
• Usage instructions: How to run and collect data

Language-Specific Patterns

Python

# Original code
def calculate_sum(a, b):
    result = a + b
    return result

# Instrumented code
import logging
logging.basicConfig(level=logging.INFO)

def calculate_sum(a, b):
    # Function entry instrumentation
    logging.info(f"ENTER calculate_sum(a={a}, b={b})")

    result = a + b
    # Variable instrumentation
    logging.info(f"VAR result={result}")

    # Function exit instrumentation
    logging.info(f"EXIT calculate_sum() -> {result}")
    return result

Java

// Original code
public int calculateSum(int a, int b) {
    int result = a + b;
    return result;
}

// Instrumented code
public int calculateSum(int a, int b) {
    // Function entry instrumentation
    System.out.println("ENTER calculateSum(a=" + a + ", b=" + b + ")");

    int result = a + b;
    // Variable instrumentation
    System.out.println("VAR result=" + result);

    // Function exit instrumentation
    System.out.println("EXIT calculateSum() -> " + result);
    return result;
}

JavaScript

// Original code
function calculateSum(a, b) {
    const result = a + b;
    return result;
}

// Instrumented code
function calculateSum(a, b) {
    // Function entry instrumentation
    console.log(`ENTER calculateSum(a=${a}, b=${b})`);

    const result = a + b;
    // Variable instrumentation
    console.log(`VAR result=${result}`);

    // Function exit instrumentation
    console.log(`EXIT calculateSum() -> ${result}`);
    return result;
}

C/C++

// Original code
int calculate_sum(int a, int b) {
    int result = a + b;
    return result;
}

// Instrumented code
#include <stdio.h>

int calculate_sum(int a, int b) {
    // Function entry instrumentation
    printf("ENTER calculate_sum(a=%d, b=%d)\n", a, b);

    int result = a + b;
    // Variable instrumentation
    printf("VAR result=%d\n", result);

    // Function exit instrumentation
    printf("EXIT calculate_sum() -> %d\n", result);
    return result;
}

Branch Instrumentation Example

# Original code
def check_value(x):
    if x > 0:
        return "positive"
    else:
        return "non-positive"

# Instrumented code
def check_value(x):
    logging.info(f"ENTER check_value(x={x})")

    # Branch instrumentation
    if x > 0:
        logging.info("BRANCH if(x > 0) -> TRUE")
        result = "positive"
    else:
        logging.info("BRANCH if(x > 0) -> FALSE")
        result = "non-positive"

    logging.info(f"EXIT check_value() -> {result}")
    return result

Configuration-Based Instrumentation

Generate a configuration file to control instrumentation:

# instrumentation_config.py
INSTRUMENTATION_ENABLED = True
INSTRUMENT_FUNCTIONS = True
INSTRUMENT_BRANCHES = True
INSTRUMENT_VARIABLES = False
LOG_LEVEL = "INFO"
OUTPUT_FORMAT = "text"  # or "json", "csv"

# Instrumented code with configuration
import instrumentation_config as config

def calculate_sum(a, b):
    if config.INSTRUMENT_FUNCTIONS:
        logging.info(f"ENTER calculate_sum(a={a}, b={b})")

    result = a + b

    if config.INSTRUMENT_VARIABLES:
        logging.info(f"VAR result={result}")

    if config.INSTRUMENT_FUNCTIONS:
        logging.info(f"EXIT calculate_sum() -> {result}")

    return result

Output Format

Probe Description Document

## Instrumentation Report

**File**: calculator.py
**Instrumentation Date**: 2024-02-17
**Configuration**: Function-level + Branch-level

### Instrumented Functions

1. **calculate_sum(a, b)**
   - Entry probe: Line 3
   - Exit probe: Line 8
   - Captures: Parameters (a, b), return value

2. **check_value(x)**
   - Entry probe: Line 11
   - Branch probe: Line 14 (if x > 0)
   - Exit probe: Line 19
   - Captures: Parameter (x), branch decision, return value

### Instrumentation Statistics
- Total functions instrumented: 2
- Total branches instrumented: 1
- Total variables instrumented: 0
- Estimated overhead: <5%

### Usage
Run the instrumented code normally. Instrumentation output will be written to:
- Console (stdout)
- Log file: instrumentation.log (if configured)

Best Practices

1. Minimize overhead: Only instrument what's necessary
2. Use conditional compilation: Allow disabling instrumentation in production
3. Handle exceptions: Ensure instrumentation doesn't crash the program
4. Preserve semantics: Never modify program logic
5. Thread-safe logging: Use thread-safe logging mechanisms
6. Structured output: Use consistent format for easy parsing
7. Timestamp everything: Include timestamps for temporal analysis

Advanced Features

Selective Instrumentation

# Only instrument specific functions
INSTRUMENTED_FUNCTIONS = ["calculate_sum", "process_data"]

def should_instrument(func_name):
    return func_name in INSTRUMENTED_FUNCTIONS

# Apply instrumentation conditionally
if should_instrument("calculate_sum"):
    # Add instrumentation
    pass

Performance Monitoring

import time

def calculate_sum(a, b):
    start_time = time.time()
    logging.info(f"ENTER calculate_sum(a={a}, b={b})")

    result = a + b

    elapsed = time.time() - start_time
    logging.info(f"EXIT calculate_sum() -> {result} [time={elapsed:.6f}s]")
    return result

JSON Output Format

import json
import time

def calculate_sum(a, b):
    entry_event = {
        "type": "function_entry",
        "function": "calculate_sum",
        "params": {"a": a, "b": b},
        "timestamp": time.time()
    }
    print(json.dumps(entry_event))

    result = a + b

    exit_event = {
        "type": "function_exit",
        "function": "calculate_sum",
        "return_value": result,
        "timestamp": time.time()
    }
    print(json.dumps(exit_event))

    return result

Constraints

• Preserve semantics: Never change program behavior
• Minimal overhead: Keep instrumentation lightweight
• No side effects: Instrumentation shouldn't modify program state
• Exception safety: Handle errors gracefully
• Configurable: Allow enabling/disabling instrumentation