0.2.5 (stable): NonDeDuplicated's generic parameter must implement Any. Docs. cross-crate-demo/. GH Actions.

Author: peter-lyons-kehl

.github/workflows/main.yml

@@ -19,14 +19,19 @@ jobs:
 
       - name: Tests and demos
         run: |
-          rustup component add clippy
+          rustup component add clippy rustfmt
           cargo clippy
+          cargo fmt --check
+          cargo doc --no-deps --quiet
           cargo test
           cargo test --release
           rustup install nightly --profile minimal
           rustup +nightly component add miri
           cargo +nightly miri test
-          demo-fat-lto/static_option_u8.sh
-          demo-fat-lto/static_str.sh
-          demo-fat-lto/literal_str.sh
+          cross-crate-demo/bin/static_option_u8.sh
+          cross-crate-demo/bin/static_str.sh
+          cross-crate-demo/bin/literal_str.sh
+          cross-crate-demo/bin-fat-lto/static_option_u8.sh
+          cross-crate-demo/bin-fat-lto/static_str.sh
+          cross-crate-demo/bin-fat-lto/literal_str.sh
         shell: sh

.gitignore

@@ -1,4 +1,3 @@
 /target
-/demo-fat-lto/target
-/demo-fat-lto/cross-crate/target
+/cross-crate-demo/*/target
 

CHANGELOG.md

@@ -1,22 +1,48 @@
 # Changelog
 
-## 0.2.3 and 0.3.3-nightly
+This reflects GIT commits on `main` branch (the default branch), that is, `stable` versions
+(compatible with `stable` Rust toolchain). Some of the below versions may not have been published to
+[crates.io](https://crates.io/crates/ndd) but were skipped.
+
+[`nightly` GIT branch](https://github.com/peter-lyons-kehl/ndd/tree/nightly) may occasionally be
+behind `main`. See also [CONTRIBUTING.md](CONTRIBUTING.md).
+
+## 0.2.6 (stable) and 0.3.6-nightly
+
+[`cross-crate-demo`](cross-crate-demo/) demonstrates effect of Fat LTO (Link Time Optimization)
+across crates. Also invoked from GitHub Actions.
+
+## 0.2.5 (stable)
+
+- `NonDeDuplicated`'s generic parameter `T` must now implement
+  [`core::any::Any`](https://doc.rust-lang.org/nightly/core/any/trait.Any.html).
+- Tests with [MIRI](https://github.com/rust-lang/miri).
+- Docs.
+
+## 0.2.4 (stable)
+
+- GitHub Actions on Alpine Linux
+- Docs; GH Actions badge in README
+- `fat lto` demo
+- [`precommit`](./pre-commit) GIT check
+
+## 0.2.3 (stable) and 0.3.3-nightly
 
 - Validation: For `static` variables only. Dropping `ndd::NonDeDuplicated` in debug build panics.
 - New tests.
 - Documentation: `nightly`, quality,
 - Versioning scheme validation: GitHub Actions.
 - Versioning scheme validation: local GIT pre-commit hook.
 
-## 0.2.2
+## 0.2.2 (stable)
 
 Documentation.
 
-## 0.2.1
+## 0.2.1 (stable)
 
 Documentation.
 
-## 0.2.0
+## 0.2.0 (stable)
 
 Initial functionality.
 

CONTRIBUTING.md

@@ -19,6 +19,11 @@ ln -s ../../pre-commit
 `nightly` functionality is on [`nightly`
 branch](https://github.com/peter-lyons-kehl/ndd/tree/nightly).
 
+### Warning about nightly
+
+`nightly` branch is subject to continuous rebase (and forced push). If you need to extend/modify
+`nightly`-specific functionality, communicate first.
+
 ## File formatting
 
 - Use `cargo fmt` for Rust source.

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "ndd"
-version = "0.2.4"
+version = "0.2.5"
 edition = "2024"
 
 license = "BSD-2-Clause OR Apache-2.0 OR MIT"

Cargo.toml

@@ -14,39 +14,48 @@ address**.
 
 Rust (or, rather, LLVM) by default de-duplicates or reuses **addresses** of `static` variables in
 `release` builds. And somewhat in `debug` builds, too. For most purposes that is good: The result
-binary is smaller, and because of more successful cache hits, the execution may be faster.
+binary is smaller, and because of more successful cache hits, the execution is faster.
 
 However, that is counter-productive when the code identifies/compares `static` data by memory
 address of the reference (whether a Rust reference/slice, or a pointer/pointer range). For example,
 an existing Rust/3rd party API may accept ("ordinary") references/slices. You may want to extend
 that API's protocol/behavior with signalling/special handling when the client sends in your
 designated `static` variable by reference/slice/pointer/pointer range. (Your special handler may
 cast such references/slices to pointers and compare them by address with
-[`core::ptr::eq()`](https://doc.rust-lang.org/nightly/core/ptr/fn.eq.html).)
-
-Then you don't want the client, nor the compiler/LLVM, to reuse/share the memory address of such a
-designated `static` for any other ("ordinary") `static` or `const` values/expressions, or local
-numerical/character/byte/string slice literals. That does work out of the box when the client passes
-a reference/slice defined as `static`: (even with the default `release` optimizations) each `static`
-gets its own memory space. See a test [`src/lib.rs` ->
+[`core::ptr::eq()`](https://doc.rust-lang.org/nightly/core/ptr/fn.eq.html) or
+[`core::ptr::addr_eq()`](https://doc.rust-lang.org/nightly/core/ptr/fn.addr_eq.html).)
+
+Then you do **not want** the client, nor the compiler/LLVM, to reuse/share the memory address of
+such a designated `static` for any other ("ordinary") `static` or `const` values/expressions, or
+local numerical/character/byte/string slice literals. That does work out of the box when the client
+passes a reference/slice defined as `static`: each `static` gets its own memory space (even with the
+default `release` optimizations). See a test [`src/lib.rs` ->
 `addresses_unique_between_statics()`](https://github.com/peter-lyons-kehl/ndd/blob/26d743d9b7bbaf41155e00174f8827efca5d5f32/src/lib.rs#L72).
 
 However, there is a problem (in `release` mode, and for some types even in `debug` mode). It affects
 ("ordinary") `const` values/expressions that equal in value to any `static` (which may be your
-designated `static`). Rust/LLVM re-uses address of one such matching `static`' for references to
+designated `static`). Rust/LLVM re-uses address of one such matching `static`' for references to any
 equal value(s) defined as `const`. See a test [`src/lib.rs` ->
 `addresses_not_unique_between_const_and_static()`](https://github.com/peter-lyons-kehl/ndd/blob/26d743d9b7bbaf41155e00174f8827efca5d5f32/src/lib.rs#L95).
-Such `const`, `static` or literal could be in 3rd party code, and even private (see
-[`demo-fat-lto`](./demo-fat-lto))!
+Such `const`, `static` or literal could be in 3rd party code, and private - not even exported (see
+[`cross-crate-demo`](cross-crate-demo))!
 
-Things get worse: `debug` builds don't have this consistent.
+Things get worse: `debug` builds don't have this consistent:
 
 - For some types (`u8`, numeric primitive-based enums) `debug` builds don't reuse `static` addresses
   for references/slices to `const` values. But
 - For other types (`str`), `debug` builds do reuse them...
-- Only `MIRI` doesn't reuse `static` addresses at all.
 
-Even worse so: `release` builds don't have this consistent.
+`MIRI` reuses `static` addresses even less (than `debug` does), but it still does reuse them
+sometimes - for example, between byte literals (`b"Hello"`) and equal string literals (`"Hello"`).
+
+Even worse so: `release` builds don't have this consistent. De-duplication across crates depends on
+"fat" link time optimization (LTO):
+
+```toml
+[profile.release]
+lto = "fat"
+```
 
 ## Solution
 
@@ -102,7 +111,8 @@ versions `1.0` or higher.
 - **Odd**-numbered major versions (`0.3`, `0.5`...)
   - always contain `-nightly` (pre-release identifier) in their name.
   - are, indeed, for `nightly` (**unstable**) functionality, and need `nightly` Rust toolchain
-    (indicated with `rust-toolchain.toml` which is present on `nightly` branch only).
+    (indicated with `rust-toolchain.toml` which is present on [`nightly`
+    branch](https://github.com/peter-lyons-kehl/ndd/tree/nightly) GIT branch only).
   - include functionality already present in some lower stable versions. Not all of them - only:
     - stable versions with a **lower major** numeric version, and
     - if the stable **major** version is lower by **`0.1` only** (and not by more), then the stable
@@ -210,22 +220,27 @@ stable not in years, but sooner.
 
 ## Quality
 
-Checked and tested (also with [MIRI](https://github.com/rust-lang/miri)):
+Checks and tests are run by [GitHub Actions (CI)](.github/workflows/main.yml). All scripts run on
+Alpine Linux and are POSIX-compliant.
+
 - `cargo clippy`
+- `cargo fmt --check`
+- `cargo doc --no-deps --quiet`
 - `cargo test`
 - `cargo test --release`
-- `rustup install nightly --profile minimal`
-- `rustup +nightly component add miri`
-- `cargo +nightly miri test`
-- `release`-only tests:
-  - `demo-fat-lto/static_option_u8.sh`
-  - `demo-fat-lto/static_str.sh`
-  - `demo-fat-lto/literal_str.sh`
-
-The versioning convention is validated:
-
-- locally with GIT [pre-commit](./pre-commit) hook, and
-- with a [GitHub action](.github/workflows/main.yml).
+- with [MIRI](https://github.com/rust-lang/miri):
+  - `rustup install nightly --profile minimal`
+  - `rustup +nightly component add miri`
+  - `cargo +nightly miri test`
+- `release`-only demonstration:
+  - `cross-crate-demo/bin/static_option_u8.sh`
+  - `cross-crate-demo/bin/static_str.sh`
+  - `cross-crate-demo/bin/literal_str.sh`
+  - `cross-crate-demo/bin-fat-lto/static_option_u8.sh`
+  - `cross-crate-demo/bin-fat-lto/static_str.sh`
+  - `cross-crate-demo/bin-fat-lto/literal_str.sh`
+- validate the versioning convention:
+  - [`pre-commit`](./pre-commit)
 
 ## Use cases
 

README.md

@@ -0,0 +1,26 @@
+# Fat LTO effect demo
+
+Demo that LLVM can de-duplicate equal `static` literals or variables and `const` even between
+crates, that is, affecting 3-rd party ("innocent") code.
+
+Run and see how `lto = "fat"` (Link Time Optimization) affects de-duplication:
+
+- same `static` and `const` values across crates, **without** `lto = "fat"`, even in standard
+  `release` build, do **not** get de-duplicated:
+  - [`bin/literal_str.sh`](bin/literal_str.sh)
+  - [`bin/static_option_u8.sh`](bin/static_option_u8.sh)
+  - [`bin/static_str.sh`](bin/static_str.sh)
+- but, same `static` and `const` values across crates, **with** `lto = "fat"`, **do** get
+  de-duplicated:
+  - [`bin-fat-lto/literal_str.sh`](bin-fat-lto/literal_str.sh)
+  - [`bin-fat-lto/static_option_u8.sh`](bin-fat-lto/static_option_u8.sh)
+  - [`bin-fat-lto/static_str.sh`](bin-fat-lto/static_str.sh)
+
+The only difference between [`bin/`](bin) and [`bin-fat-lto/`](bin-fat-lto) is in their
+`Cargo.toml`:
+
+- [`bin-fat-lto/Cargo.toml`](bin-fat-lto/Cargo.toml) uses `lto = "fat"`, but
+- [`bin/Cargo.toml`](bin/Cargo.toml) does not.
+
+This requires a filesystem that supports symlinks. ([`bin`](bin) and [`bin-fat-lto`](bin-fat-lto)
+use symlinks to reuse files from [`bin-shared`](bin-shared).

cross-crate-demo/README.md

@@ -1,13 +1,14 @@
 [package]
-name = "demo-fat-lto"
+name = "bin"
 version = "0.1.0"
 edition = "2024"
 
 [dependencies]
-cross-crate = {path = "cross-crate" }
+callee = {path = "../callee" }
 
 [lints.rust]
 unexpected_cfgs = { level = "forbid"}
 
 [profile.release]
 lto = "fat"
+