[bug][nn.CrossEntropyLoss] Wrong-shaped target causes internal CHECK failure (is_initialized()) and abort instead of shape-mismatch error

[tinywisdom]

Summary

Passing a wrongly shaped target y to nn.CrossEntropyLoss (e.g., logits with shape (N, C) but y has shape (1,) instead of (N,)) triggers an internal assertion:

oneflow::CHECK failed: is_initialized()

and eventually aborts with a core dump, instead of raising a clear, user-facing shape mismatch exception. This happens in eager forward; Graph mode would hit the same failure at the same call site.

Code to reproduce bug

import oneflow as flow
import oneflow.nn as nn

# Model: Linear -> CrossEntropy, forward only
class M(nn.Module):
    def __init__(self):
        super().__init__()
        self.fc = nn.Linear(10, 5)
        self.ce = nn.CrossEntropyLoss()

    def forward(self, x, y):
        logits = self.fc(x)          # (4, 5)
        # Intentionally wrong shape for y; should be (4,)
        return self.ce(logits, y)

# Graph wrapper (same crash point if enabled)
class G(nn.Graph):
    def __init__(self, m):
        super().__init__()
        self.m = m
    def build(self, x, y):
        return self.m(x, y)

def main():
    flow.manual_seed(0)
    m = M()
    x = flow.randn(4, 10)
    y_bad = flow.tensor([0], dtype=flow.long)  # WRONG: should be (4,)

    print("---- Eager forward (expected to fail) ----")
    _ = m(x, y_bad)

    # To test Graph mode as well:
    # g = G(m)
    # _ = g(x, y_bad)

if __name__ == "__main__":
    main()

Observed Error (abridged)

RuntimeError: Check failed: (is_initialized())
  ... functional::cross_entropy(...)
  ... functional::impl::CrossEntropyFunctor::operator()(...)
  ... functional::Reshape(...)
  ... functional::impl::ReshapeFunctor::operator()(...)
  File "oneflow/core/common/shape.h", line 140, in NumAxes
    CHECK_OR_THROW(is_initialized())
terminate called after throwing an instance of 'oneflow::Exception'
what(): Check failed: (is_initialized())
... vm::EagerBlobObject::TryAllocateBlobBodyMemory ...
Aborted (core dumped)

System Information

• OS: Ubuntu 22.04.4 LTS (x86_64)
• OneFlow version : 1.0.0.dev20250921+cpu
• Python version: 3.10.16