Having these definitions in two different places is silly, especially
when they must be identical. If they ever got out of sync, there would
be problems.
Servo needs to know whether C++ code is compiled with MOZ_DEBUG, and
passing along an explicit feature is a better way to determine that
information than relying on cfg(debug_assertions).
MozReview-Commit-ID: B3XCskDQ56p
Doing this gets us all of the benefits that we want from Cargo
workspaces (only compiling artifacts from gkrust-shared one time for
both libraries) without all the hassles that using Cargo workspaces
would require. We don't have to worry about multiple Cargo processes
running simultaneously and racing to write files; Cargo is smart enough
to lock the build directory to serialize access to it.
268fa5f3bc25 grafted an old patch to define --features=servo in
rules.mk. That patch was written before RUST_LIBRARY_FEATURES
existed. This commit fixes it up.
MozReview-Commit-ID: L5atm5CsP8d
This patch is really two separate changes.
The first change is that rust crates are large, standalone entities that
may contain multitudes of source files. It therefore doesn't make sense
to keep them in SOURCES, as we have been doing. Moving to use cargo
will require a higher-level approach, which suggests that we need a
different, higher-level representation for Rust sources in the build
system.
The representation here is to have the build system refer to things
defined in Cargo.toml files as the entities dealt with in the build
system, and let Cargo deal with the details of actually building things.
This approach means that adding a new crate to an existing library just
requires editing Rust and Cargo.toml files, rather than dealing with
moz.build, which seems more natural to Rust programmers. By having the
source files for libraries (and binaries in subsequent iterations of
this support) checked in to the tree, we can also take advantage of
Cargo.lock files.
The second is that we switch the core build system over to building via
cargo, rather than invoking rustc directly.
We also clean up a number of leftover things from the Old Way of doing
things. A number of tests are added to confirm that we'll only permit
crates to be built that have dependencies in-tree.
This patch is really two separate changes.
The first change is that rust crates are large, standalone entities that
may contain multitudes of source files. It therefore doesn't make sense
to keep them in SOURCES, as we have been doing. Moving to use cargo
will require a higher-level approach, which suggests that we need a
different, higher-level representation for Rust sources in the build
system.
The representation here is to have the build system refer to things
defined in Cargo.toml files as the entities dealt with in the build
system, and let Cargo deal with the details of actually building things.
This approach means that adding a new crate to an existing library just
requires editing Rust and Cargo.toml files, rather than dealing with
moz.build, which seems more natural to Rust programmers. By having the
source files for libraries (and binaries in subsequent iterations of
this support) checked in to the tree, we can also take advantage of
Cargo.lock files.
The second is that we switch the core build system over to building via
cargo, rather than invoking rustc directly.
We also clean up a number of leftover things from the Old Way of doing
things. A number of tests are added to confirm that we'll only permit
crates to be built that have dependencies in-tree.
