Static Analysis

Static analysis in the Zephir compiler is a powerful tool that helps developers identify potential issues and improve code quality before runtime. Two key aspects of static analysis in Zephir are:

Conditional Unassigned Variables

Zephir's static analysis checks for situations where a variable might be used before it's assigned. Consider the following example:

class Utils
{
    public function someMethod(b)
    {
        string a; char c;

        if b == 10 {
            let a = "hello";
        }

        // a could be uninitialized here
        for c in a {
            echo c, PHP_EOL;
        }
    }
}

In this example, the variable a is conditionally assigned only when b is equal to 10. However, the subsequent loop uses the value of a, and it could be uninitialized. Zephir's static analysis detects this and generates a warning:

Warning: Variable 'a' was assigned for the first time in conditional branch,
consider initializing it in its declaration in
/home/scott/test/test/utils.zep on 21 [conditional-initialization]

    for c in a {

This warning alerts the developer to a potential issue, and Zephir automatically initializes the variable to an empty string to avoid unexpected behavior.

Dead Code Elimination

Zephir's static analysis identifies unreachable code and performs dead code elimination. Unreachable code is code that can never be executed. Here's an example:

class Utils
{
    public function someMethod(b)
    {
        if false {
            // This code is never executed
            echo "hello";
        }
    }
}

In this case, the if false condition ensures that the code inside the block is never executed. Zephir's static analysis detects this and eliminates the dead code, optimizing the generated binary.

Using static analysis helps Zephir developers catch potential bugs and improve code quality by providing early warnings and optimizations. This proactive approach contributes to a more reliable and efficient codebase.

Zephir's compiler provides static analysis of the compiled code. The idea behind this feature is to help the developer to find potential problems and avoid unexpected behaviors, well before runtime.

Conditional Unassigned Variables

Static Analysis of assignments tries to identify if a variable is used before it's assigned:

class Utils
{
    public function someMethod(b)
    {
        string a; char c;

        if b == 10 {
            let a = "hello";
        }

        //a could be unitialized here
        for c in a {
            echo c, PHP_EOL;
        }
    }
}

The above example illustrates a common situation. The variable a is assigned only when b is equal to 10, then it's required to use the value of this variable - but it could be uninitialized. Zephir detects this, automatically initializes the variable to an empty string, and generates a warning alerting the developer:

Warning: Variable 'a' was assigned for the first time in conditional branch,
consider initialize it in its declaration in
/home/scott/test/test/utils.zep on 21 [conditional-initialization]

    for c in a {

Finding such errors is sometimes tricky, however static analysis helps the programmer to find bugs in advance.

Dead Code Elimination

Zephir informs the developer about unreachable branches in the code and performs dead code elimination, which means it gets rid of all that code from the generated binary, since it cannot be executed anyway:

class Utils
{
    public function someMethod(b)
    {
        if false {
            // This is never executed
            echo "hello";
        }
    }
}