compiler: add 'b_time64' base option - #15008
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Introduce a new base option called `b_time64`. This is a boolean option,
which defaults to `false` (in which case it has no effect). If set to
true, this will set `_TIME_BITS=64` (or equivalent) for all
compilations.
This enables a workaround for the Y2038 problem. With `_TIME_BITS=64`,
libc will switch `time_t` and other relevant time types to 64-bits, if
not already 64-bit (i.e., this usually only affects 32-bit platforms).
libc will also transparently switch to 64-bit syscalls.
For more background information, there is an LWN article about it (from
10 years ago):
https://lwn.net/Articles/664800/
Handling of this option is similar to _FILE_OFFSET_BITS=64, which meson
sets by default. Unfortunately, `time_t` is much more often used in
public APIs, and thus more likely to lead to ABI mismatches when mixing
code compiled with and without the option.
Contributor
Author
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(update: fixed get_option() invocation) |
Contributor
Author
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I would welcome any help in how to properly query the option without having a build target. All my attempts seem to fail so far. |
Contributor
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Can you just skip the call to |
dcbaker
requested changes
Oct 24, 2025
| """ | ||
| return [] | ||
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| def get_time64_args(self) -> T.List[str]: |
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We usually implement these as something like:
def get_time64_args(self, enable: bool) -> T.List[str]:
return ['-D_TIME_BITS=64'] if enable else []So that you don't have to have the check in every caller.
| time64 = state.get_option('b_time64', state.subproject) | ||
| assert isinstance(time64, bool), 'for mypy' | ||
| if time64: | ||
| clang_args.append('-D_TIME_BITS=64') |
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We had a recent change here that with the _FILE_OFFSET bits maybe we can add this to the same block? (it uses the CCompiler instance so we avoid the need to copy the define here)
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Introduce a new base option called
b_time64. This is a boolean option, which defaults tofalse(in which case it has no effect). If set to true, this will set_TIME_BITS=64(or equivalent) for all compilations.This enables a workaround for the Y2038 problem. With
_TIME_BITS=64, libc will switchtime_tand other relevant time types to 64-bits, if not already 64-bit (i.e., this usually only affects 32-bit platforms). libc will also transparently switch to 64-bit syscalls.For more background information, there is an LWN article about it (from 10 years ago):
Handling of this option is similar to _FILE_OFFSET_BITS=64, which meson sets by default. Unfortunately,
time_tis much more often used in public APIs, and thus more likely to lead to ABI mismatches when mixing code compiled with and without the option.NB: This is a draft, as I have not spent too much time figuring out whether this should be a boolean option, or a choice-option (so you can override the value with
32), and whether this needs support for other languages. This is mostly to start a discussion around the feature.