This is a follow up to #3182 which introduced a new way of
conditionally including code based on the compiler version.
When originally reviewing I missed the fact that the two loops were
controlled by the current compiler version (`minor`) so the created
macro is different dependent on the compiler used to build the code.
To help the next guy notice, add a comment.
Conditional compilation depending on Rust version using `cfg` had the
disadvantage that we had to write the same code multiple times, compile
it multiple times, execute it multiple times, update it multiple
times... Apart from obvious maintenance issues the build script wasn't
generating the list of allowed `cfg`s so those had to be maintained
manually in `Cargo.toml`. This was fixable by printing an appropriate
line but it's best to do it together with the other changes.
Because we cannot export `cfg` flags from a crate to different crates we
take a completely different approach: we define a macro called
`rust_version` that takes a very naturally looking condition such as
`if >= 1.70 {}`. This macro is auto-generated so that it produces
different results based on the compiler version - it either expands to
first block or the second block (after `else`).
This way, the other crates can simply call the macro when needed.
Unfortunately some minimal maintenance is still needed: to update the
max version number when a newer version is used. (Note that code will
still work with higher versions, it only limits which conditions can be
used in downstream code.) This can be automated with the pin update
script or we could just put the pin file into the `internals` directory
and read the value from there. Not automating isn't terrible either
since anyone adding a cfg with higher version will see a nice error
about unknown version of Rust and can update it manually.
Because this changes syntax to a more naturally looking version number,
as a side effect the `cond_const` macro could be also updated to use the
new macro under the hood, providing much nicer experience - it is no
longer needed to provide human-readable version of the version string to
put in the note about `const`ness requiring a newer version. As such the
note is now always there using a single source of truth.
It's also a great moment to introduce this change right now since
there's currently no conditional compilation used in `bitcoin` crate
making the changes minimal.
Rust version 1.56.0 introduced edition 2021. Shortly afterwards, on
October 21 2021 Rust version 1.56.1 was released.
Debian stable is currently shipping `rustc 1.63.0`.
Our stated MSRV policy is: In Debian stable and at least 2 years old.
Therefore our MSRV policy is met by Rust version 1.56.1 and we can strat
to bump our MSRV org wide.
Start by bumping the `rust-bitcoin` and `hashes` MSRV to Rust 1.56.1,
includes:
- Update docs.
- Update CI and remove pinning.
- Update the build files and remove now stale cfg attributes rust_v_1_x
for values less than the new MSRV.
- Use new `IntoIterator` for arrays so we no longer need to allocate a
vector to iterate.
Links:
- https://blog.rust-lang.org/2021/11/01/Rust-1.56.1.html
- https://blog.rust-lang.org/2021/10/21/Rust-1.56.0.html
- https://packages.debian.org/stable/rust/rustc
Previously, each unique compiler cfg attribute that appeared in the
codebase was hard coded and emitted to stdout at compile time. This
meant keeping the file up to date as different compiler cfg attributes
changed. It's inconsequential to emit a compiler version that's not
used, so this change just emits all possibilities to reduce the
maintenance burden of the build script.
This implements basic facilities to conditionally carry string inputs in
parse errors. This includes:
* `InputString` type that may carry the input and format it
* `parse_error_type!` macro creating a special type for parse errors
* `impl_parse` implementing parsing for various types as well as its
`serde`-supporting alternative
This adds a build script that automatically activates the cfg if the
version is sufficient. We don't make API changes here, just improve
debugging by enabling `track_caller`.
Fmt Bot
Tobin C. Harding
Martin Habovstiak
yancy
Jamil Lambert, PhD
yancy