Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Fix recompiles of stale dependencies and cyclic graphs #1242

Merged
merged 2 commits into from
Jan 29, 2015
Merged

Fix recompiles of stale dependencies and cyclic graphs #1242

merged 2 commits into from
Jan 29, 2015

Commits on Jan 29, 2015

  1. Consider transitive fingerprints for freshness 

    Originally discovered through rust-lang#1236, this commit fixes a bug in Cargo where
crates may not be recompiled when they need to (leading to obscure errors from
the compiler). The scenario in question looks like:

* Assume a dependency graph of `A -> B -> C` and `A -> C`
* Build all packages
* Modify C
* Rebuild, but hit Ctrl+C while B is building
* Modify A
* Rebuild again

Previously, Cargo only considered the freshness of a package to be the freshness
of the package itself (checking source files, for example). To handle transitive
recompilations, Cargo propagates a dirty bit throughout the dependency graph
automatically (instead if calculating it as such).

In the above example, however, we have a problem where as part of the last
rebuild Cargo thinks `B` and `C` are fresh! The artifact for `C` was just
recompiled, but `B`'s source code is untainted, so Cargo does not think that it
needs to recompile `B`. This is wrong, however, because one of `B`'s
dependencies was rebuilt, so it needs to be rebuilt.

To fix this problem, the fingerprint (a short hash) for all packages is now
transitively propagated (the fingerprint changes when an upstream package
changes). This should ensure that even when Ctrl+C is hit (or the situation
explained in rust-lang#1236) that Cargo will still consider packages whose source code is
untainted as candidates for recompilation.

The implementation is somewhat tricky due to the actual fingerprint for a path
dependency not being known until *after* the crate is compiled (the fingerprint
is the mtime of the dep-info file).

Closes rust-lang#1236
    @alexcrichton
    alexcrichton committed Jan 29, 2015
    Configuration menu
    Copy the full SHA
    a40d3b0 View commit details
    Browse the repository at this point in the history

  2. Forbid cyclic dependencies 

    Re-jigger some code in the resolver and refactor a little bit to get the
ordering of checks right to forbid cyclic dependencies from ever reaching the
backend.

Closes rust-lang#834
    @alexcrichton
    alexcrichton committed Jan 29, 2015
    Configuration menu
    Copy the full SHA
    06f37a0 View commit details
    Browse the repository at this point in the history