Define the input stack format in Miniscript: A guide
Miniscript is a popular programming language used to build distributed applications on the Polkadot network. When creating or compiling Miniscript scripts, one of the key aspects to understand is how to define the input stack format.
In this article, we will explore the concept of input stack formats in Miniscript and explore the implications of different calling conventions when crafting a convention.
What is an input stack format?
An input stack format refers to the structure that the compiler uses to represent the arguments passed to a function call. In other words, a function takes its inputs from the environment and passes them back out as results.
In Miniscript, the input stack format is determined by the calling method of the function being called. The calling convention defines how the function takes its inputs and passes them.
Calling Convention Types
There are two primary calling conventions in Miniscript:
- C-Style: This is the most common calling convention, where each argument is passed as a separate value on the stack.
- Packed: In this convention, multiple arguments can be packed into a single stack location.
Specify the input stack format
When compiling a convention, the compiler must perform its own validation to ensure that the input stack format matches the expected calling convention for each function call. The compiler uses this information to validate the inputs and outputs of the functions.
However, there is no single “exact” or “universal” way to determine the input stack format. Instead, the compiler must consult a number of sources, including:
- Function Documentation: Many Miniscript function definitions have a “documentation” field that can provide information about the expected input and output formats.
- Compiler Settings: The compile command and settings can also affect the shape of the input stack.
Example Use Case
Suppose we want to compile a routine that calls the function “miniscript-minicall” with two arguments:
function main() {
var arg1 = "Hello";
var argument2 = 42;
}
If we run the following command in our editor, we will see a summary of the input stack format:
> minimal slim
Miniscript compiler: v0.11.6
Input stack format:
argument1 int
argument2 uint8
result int
From this output, we can conclude that the “minicall” function expects two arguments on the stack, where “arg1” is an integer and “arg2” is a 256-bit unsigned integer.
Conclusion
Determining the input stack format in Miniscript is a complex process involving several factors, including function documentation, compiler settings, and user-entered values. While there is no single “universal” way to determine the input stack format, understanding these sources of information can help you write more robust and efficient code.
As developers, we need to ensure that our practices follow the expected calling conventions for each function call to avoid potential input validation issues, data corruption, or other problems.