PyOpenCL 2026.1.2 compiler cache fails on Python 3.12.13 with `TypeError: %b requires a bytes-like object`

[GianmarcoMidena]

Summary

When building an OpenCL program with PyOpenCL compiler caching enabled, PyOpenCL emits a warning because cache compilation fails internally while trying to append the cache-defeating constant to the source.

The build appears to continue, but compiler caching is disabled for that build.

Environment

• OS: Linux 7.0.0-28-generic x86_64, glibc 2.39
• Python: 3.12.13 from conda-forge
• PyOpenCL: 2026.1.2
• OpenCL platform: Intel(R) OpenCL Graphics
• OpenCL device: Intel(R) Iris(R) Xe Graphics
• OpenCL version: OpenCL 3.0 NEO
• Driver: 24.52.032224

Exception

UserWarning: PyOpenCL compiler caching failed with an exception:
[begin exception]
Traceback (most recent call last):
  File ".../site-packages/pyopencl/cache.py", line 514, in create_built_program_from_source_cached
    _create_built_program_from_source_cached(
  File ".../site-packages/pyopencl/cache.py", line 424, in _create_built_program_from_source_cached
    src = src + b"\n\n__constant int pyopencl_defeat_cache_%s = 0;" % (
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: %b requires a bytes-like object, or an object that implements __bytes__, not 'str'
[end exception]

Suspected Cause

In pyopencl/cache.py, the source is encoded to bytes first:

if isinstance(src, str):
    src = src.encode()

but then the bytes format string uses %s with uuid4().hex, which is a Python str:

src = src + b"\n\n__constant int pyopencl_defeat_cache_%s = 0;" % (
        uuid4().hex)

Expected Behavior

PyOpenCL compiler caching should build and cache the program without emitting a warning.

Actual Behavior

PyOpenCL emits a warning because compiler caching fails with:

TypeError: %b requires a bytes-like object, or an object that implements __bytes__, not 'str'