sfpy-asm 0.1.0

Experimental GCC/GAS inline assembly bridge for Python

sfpy-asm(Segmentation Fault in Python)

Experimental Python bridge for GCC/GAS-style extended inline assembly.

from sfpy import __asm__

result = __asm__(
    "addq %1, %0",
    [("+r", 40)],
    [("r", 2)],
    ["cc"],
)

assert result == 42

Only __asm__ is exported from sfpy.

API

__asm__(code: str, outputs=None, inputs=None, clobbers=None)

• code: GCC extended inline assembly template. GAS syntax is accepted by GCC.
• outputs: list of (constraint, value) output operands.
• inputs: list of (constraint, value) input operands.
• clobbers: list of register/clobber names such as ["rax", "memory", "cc"].

Return value:

• no outputs: None
• one output: that value
• multiple outputs: tuple of values

Supported operand values:

• int, bool: native long long
• float: native double
• str: UTF-8 const char *
• bytes, bytearray: byte buffer pointer
• any other object: raw PyObject *
• Python callables used as inputs: native no-argument callback pointer returning long long

Python variables cannot be mutated through GCC output operands, so output operands are returned instead. For read/write constraints such as "+r", the supplied output value is used as the initial native value.

Callable operands are plain native function pointers. Call them from assembly with call *%N. Because GCC cannot see that call, include the usual caller-saved register clobbers yourself:

def answer():
    return 42

result = __asm__(
    "call *%1\nmovq %%rax, %0",
    [("=r", 0)],
    [("r", answer)],
    ["rax", "rcx", "rdx", "rsi", "rdi", "r8", "r9", "r10", "r11", "memory", "cc"],
)

This package is Linux/WSL-only and requires gcc plus Python development headers at runtime because __asm__ compiles a small shared object for each assembly signature.