[libc] Handle overflow in localtime and gmtime#27187
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Modify `_localtime_js` and `_gmtime_js` to return success/failure status, and update `__localtime_r` and `__gmtime_r` to return NULL when they fail. Previously, these JS helper functions returned `void` and would write invalid/NaN values to the `tm` struct when the input time was out of range of the JS `Date` object. This could trigger assertions or result in garbage data. This completes the work started in 722a1b7 (which fixed `mktime` but left `localtime`/`gmtime` unhandled). Added tests to verify: - `localtime` and `gmtime` return NULL on overflow. - `localtime_r` does not modify the `tm` struct on failure. See: emscripten-core#26704
kripken
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Jun 26, 2026
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Modify
_localtime_jsand_gmtime_jsto return success/failure status, and update__localtime_rand__gmtime_rto return NULL when they fail.Previously, these JS helper functions returned
voidand would write invalid/NaN values to thetmstruct when the input time was out of range of the JSDateobject. This could trigger assertions or result in garbage data.This completes the work started in #26704 (which fixed
mktimebut leftlocaltime/gmtimeunhandled).Added tests to verify:
localtimeandgmtimereturn NULL on overflow.localtime_rdoes not modify thetmstruct on failure.See: #26704