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Apply defines to struct literal #956

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Fix #955

@youknowone youknowone force-pushed the cfg-literal branch 3 times, most recently from cc3bb3f to 0e7afe1 Compare May 17, 2024 10:25
Comment on lines 13 to 26
#[repr(C)]
pub struct Bar {
pub x: i32,
#[cfg(windows)]
pub y: u32,
}

impl Bar {
pub const BAR: Self = Self {
x: 0,
#[cfg(windows)]
y: 0,
};
}
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How can I properly add a test? This change doesn't add diff

@youknowone
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I didn't push newline/indent fix not to break test yet. Please let me know if the approach is okay. Then I will finish the whitespace work.

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Thanks, looks good with a question.

Regarding the test, let's put it in tests/rust/cfg.rs.

Feel free to remove tests/rust/cfg_field.rs, it was meant as a crashtest at some point, looking at the git history, but right now it's covered by tests/rust/cfg.

// In C++, same order as defined is required.
let ordered_fields = out.bindings().struct_field_names(path);
for ordered_key in ordered_fields.iter() {
let last_i = ordered_fields.len() - 1;
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Ah, the question didn't get saved. It's basically... can't this underflow? It'd be better to do if ordered_fields.is_empty() { 0 } else { ordered_fields.len() - 1 };

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Ah, it might be harder than that... Recording with a bit whether we have conditional fields, and either skip generating the constant or generate it without the conditions for C seems feasible.

Alternatively doing some macro soup for C might work but it is annoying. Something like gathering the conditional fields first, and generating something like:

#ifdef X11
#define zero_(v) .zero = v,
#else
#define zero_(v)
#endif
#define ConditionalField_ZERO (ConditionalField){ \
  zero_(0) \
};

Or so, but that gets clunky.

tests/expectations/cfg.compat.c Show resolved Hide resolved
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Thank you for the advice. It had progress, but not yet finished.

I left another comment for duplicated field generation.
Another problem is constexpr context. write_literal needs context about allow_constexpr to choose macro or inline field. Do you have a suggestion for that? This is solved

Comment on lines 959 to 979
if self.config.language == Language::C {
for ordered_key in ordered_fields.iter() {
if let Some(lit) = fields.get(ordered_key) {
if let Some(condition) = lit.cfg.to_condition(self.config) {
out.new_line();
condition.write_before(self.config, out);
let define = format!("#define __{export_name}_{ordered_key}(v)");
write!(out, "{define} (v)");
write!(out, "\n#else\n");
write!(out, "{define}");
condition.write_after(self.config, out);
}
}
}
}
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@youknowone youknowone Aug 10, 2024

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Where is the good place to put this?
From this place, it will write duplicated definitions for each literal definition. That will trigger compiler warnings about redefinition.

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@emilio This part is also not resolved yet

@@ -911,30 +911,42 @@ impl LanguageBackend for CLikeLanguageBackend<'_> {
fields,
path,
} => {
let is_constexpr = self.config.language == Language::Cxx
&& (self.config.constant.allow_constexpr || l.can_be_constexpr());
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This seems wrong? Shouldn't it be allow_constexpr && can_be_constexpr?

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Oh.. I was confused by allow_static_const. Thank you

if is_constexpr {
if i > 0 {
write!(out, ", ");
}
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Factor this out of the if/else?

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If you looked in first commit, this is changed in second commit

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If you don't mind, I separated the former 2 commits to another PR in #988, which is not directly related to cfg handling.

} else {
write!(out, ".{} = ", ordered_key);
}
self.write_literal(out, lit);
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Same here.

#else
#define __ConditionalField_field(v)
#endif
#define ConditionalField_ONE (ConditionalField){ .field = __ConditionalField_field(1) }
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Does this even build when it's not defined? Doesn't it expand to .field =?

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Thanks, fixed it

@youknowone
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@emilio could you take another look?

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defines is not applied for impl const
2 participants