dotnet/runtime · error · Exception

Could not determine JIT-EE version

Error message

Could not determine JIT-EE version

What it means

Raised by superpmi_diffs_setup.py build_partitions() at src/coreclr/scripts/superpmi_diffs_setup.py:232 when `mcs -printJITEEVersion` returns a non-zero exit code. mcs (method context sorter) is expected to print the JIT-EE version string used to locate the matching baseline collection in Azure blob storage.

Solutions

1. Confirm mcs exists at bin_path (and the osx.x64.Checked override path on macOS).
2. Rebuild coreclr Checked for the target OS/arch so mcs is fresh.
3. Run `mcs -printJITEEVersion` manually to see the real failure (missing .so/.dll, segfault).
4. Ensure bin_path matches the build output layout.

import os, subprocess
mcs_path = os.path.join(bin_path, 'mcs.exe' if is_windows else 'mcs')
if not os.path.isfile(mcs_path):
    raise SystemExit(f'mcs not found at {mcs_path} — build coreclr Checked first')
rc = subprocess.run([mcs_path, '-printJITEEVersion']).returncode
if rc != 0:
    raise SystemExit(f'mcs -printJITEEVersion exited {rc} — inspect the binary')

try:
    jit_ee_version = subprocess.check_output([mcs_path, '-printJITEEVersion'], text=True).strip().lower()
except subprocess.CalledProcessError:
    raise RuntimeError('Could not determine JIT-EE version')

When it happens

Trigger: The mcs binary is missing/corrupt, fails to run on the host, or returns non-zero from -printJITEEVersion; bin_path points to the wrong directory.

Common situations: CoreCLR Checked build not produced for the target; wrong bin_path; running an mcs built for a different OS/arch; missing shared libraries required by mcs.

Related errors

• Cannot find System.Private.CoreLib.dll at
• Collection 'smoke_tests' is only available for 'nativeaot'…
• {coreclr_args.mode}
• Invalid arch.
• Pass only one tiering option.

AI-assisted analysis of dotnet/runtime@60108ba66e (2026-08-10). Data as JSON: /api/errors/4259c911243a558f. Report an issue: GitHub.

Appendix: source

Thrown at src/coreclr/scripts/superpmi_diffs_setup.py:232

        return 1

def build_partitions(partitions_dir, do_asmdiffs, bin_path, host_bitness):
    mcs_path = os.path.join(bin_path, "mcs.exe" if is_windows else "mcs")
    if is_macos:
        # Hack: the target is arm64, but the build machine is x64. We build SPMI for x64 because of that,
        # but it exists at a different path.
        mcs_path = os.path.join(bin_path, "..", "osx.x64.Checked", "mcs")
    assert(os.path.exists(mcs_path))

    command = [mcs_path, "-printJITEEVersion"]
    proc = subprocess.Popen(command, stdout=subprocess.PIPE)
    stdout_jit_ee_version, _ = proc.communicate()
    return_code = proc.returncode
    if return_code == 0:
        jit_ee_version = stdout_jit_ee_version.decode('utf-8').strip()
        jit_ee_version = jit_ee_version.lower()
    else:
        raise Exception("Could not determine JIT-EE version")

    print("JIT-EE version determined to be {}".format(jit_ee_version))

    az_account_name = "clrjit2"
    az_superpmi_container_name = "superpmi"
    az_blob_storage_account_uri = "https://" + az_account_name + ".blob.core.windows.net/"
    az_blob_storage_superpmi_container_uri = az_blob_storage_account_uri + az_superpmi_container_name
    az_collections_root_folder = "collections"
    prefix = az_collections_root_folder + "/" + jit_ee_version
    prefix_urlencoded = urllib.parse.quote(prefix)
    list_superpmi_container_uri = az_blob_storage_superpmi_container_uri + "?restype=container&comp=list&prefix=" + prefix_urlencoded + "/"

    try:
        contents = urllib.request.urlopen(list_superpmi_container_uri).read().decode('utf-8')
    except Exception as exception:
        raise Exception("Didn't find any collections using %s", list_superpmi_container_uri)

    elem = ET.fromstring(contents)

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