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Appease MSVC Warning C4866: compiler may not enforce left-to-right evaluation order #5953

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Merged
rwgk merged 4 commits into from
Jan 8, 2026
+8 −3
Merged

Appease MSVC Warning C4866: compiler may not enforce left-to-right evaluation order #5953

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fa61b54
Appease MSVC Warning C4866: compiler may not enforce left-to-right ev…
XuehaiPan Jan 7, 2026
a3a2e4d
Remove const qualifier
XuehaiPan Jan 7, 2026
1ebe0e2
Reword comment to be self-explanatory without PR context
rwgk Jan 7, 2026
f16de66
chore(deps): switch typos to mirror repo
rwgk Jan 7, 2026
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6 changes: 4 additions & 2 deletions .pre-commit-config.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -119,8 +119,10 @@ repos:
args: ["-x.codespell-ignore-lines", "-Lccompiler,intstruct"]

# Also check spelling
- repo: https://github.com/crate-ci/typos
rev: v1
# Use mirror because pre-commit autoupdate confuses tags in the upstream repo.
# See https://github.com/crate-ci/typos/issues/390
- repo: https://github.com/adhtruong/mirrors-typos
rev: "v1.41.0"
hooks:
- id: typos
args: []
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5 changes: 4 additions & 1 deletion include/pybind11/pybind11.h
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Expand Up @@ -1081,7 +1081,10 @@ class cpp_function : public function {
dict kwargs;
for (size_t i = 0; i < used_kwargs.size(); ++i) {
if (!used_kwargs[i]) {
kwargs[PyTuple_GET_ITEM(kwnames_in, i)] = args_in_arr[n_args_in + i];
// Fetch value before indexing into kwargs to ensure well-defined
// evaluation order (MSVC C4866).
PyObject *const arg_in_arr = args_in_arr[n_args_in + i];
kwargs[PyTuple_GET_ITEM(kwnames_in, i)] = arg_in_arr;
Comment on lines +1084 to +1087
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@XuehaiPan XuehaiPan Jan 8, 2026

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The warning still exists. The problem may be that the order of key casting and assignment is not well-defined.

  C:\Users\runneradmin\AppData\Local\Temp\pip-build-env-tsdbyp__\overlay\Lib\site-packages\pybind11\include\pybind11\pybind11.h(1087,1): error C2220: the following warning is treated as an error [C:\Users\runneradmin\AppData\Local\Temp\tmph2yqzrcl.build-temp\Release\src\_C.vcxproj]
  C:\Users\runneradmin\AppData\Local\Temp\pip-build-env-tsdbyp__\overlay\Lib\site-packages\pybind11\include\pybind11\pybind11.h(1087,1): warning C4866: compiler may not enforce left-to-right evaluation order for call to 'pybind11::detail::object_api<pybind11::handle>::operator[]' [C:\Users\runneradmin\AppData\Local\Temp\tmph2yqzrcl.build-temp\Release\src\_C.vcxproj]

}
}
call.args.push_back(kwargs);
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