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Document --show-type-layout in the rustdoc book #89164

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Merged
merged 4 commits into from
Sep 22, 2021
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Document --show-type-layout in the rustdoc book #89164

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71a4add
Document `--show-type-layout` in the rustdoc book
camelid Sep 22, 2021
57399e2
Fix inconsistent heading level in the rustdoc book
camelid Sep 22, 2021
490a8cf
rustdoc: Note that type layout may differ between compilations
camelid Sep 22, 2021
fcb837b
rustdoc: Emphasize "completely unstable"
camelid Sep 22, 2021
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2 changes: 1 addition & 1 deletion src/librustdoc/html/render/print_item.rs
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Expand Up @@ -1663,7 +1663,7 @@ fn document_type_layout(w: &mut Buffer, cx: &Context<'_>, ty_def_id: DefId) {
writeln!(
w,
"<div class=\"warning\"><p><strong>Note:</strong> Most layout information is \
completely unstable and may be different between compiler versions and platforms. \
completely unstable and may even differ between compilations. \
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How can this be true? The compiler has to be able to depend on the ABI to create dynamic libraries.

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From the Reference (emphasis mine):

Type layout can be changed with each compilation. Instead of trying to document exactly what is done, we only document what is guaranteed today.

I assume that means that the compiler is free to change layout if your crate is a static library or a binary. Also, there are (future) flags like -Z randomize-layout which would change layout between compilations.

The only exception is types with certain <code>repr(...)</code> attributes. \
Please see the Rust Reference’s \
<a href=\"https://doc.rust-lang.org/reference/type-layout.html\">“Type Layout”</a> \
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