remap-path-prefix affects dep-info #63329
Labels
A-driver
Area: rustc_driver that ties everything together into the `rustc` compiler
C-bug
Category: This is a bug.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
Comments
jonas-schievink
added
A-driver
Centril
added a commit
to Centril/rust
that referenced
this issue
Aug 8, 2019
…ichton Don't use remap-path-prefix in dep-info files. This changes it so that dep-info files do not use remapped paths. Having remapped paths causes problems with Cargo because if you remap to a nonexistent path (like `/rustc/$HASH` which rustc distributions do), then Cargo's change tracking thinks the files don't exist and will always rebuild. I don't actually know if this is a good idea. I think it makes sense, but I do not know what the exact requirements are for reproducible builds. I consider these files separate from the binary artifacts generated, and as a build-system helper, so it seems reasonable to me. I'm also not sure if this needs a test. I'll definitely add one on the cargo side if this is merged. Closes rust-lang#63329
Centril
added a commit
to Centril/rust
that referenced
this issue
Aug 8, 2019
…ichton Don't use remap-path-prefix in dep-info files. This changes it so that dep-info files do not use remapped paths. Having remapped paths causes problems with Cargo because if you remap to a nonexistent path (like `/rustc/$HASH` which rustc distributions do), then Cargo's change tracking thinks the files don't exist and will always rebuild. I don't actually know if this is a good idea. I think it makes sense, but I do not know what the exact requirements are for reproducible builds. I consider these files separate from the binary artifacts generated, and as a build-system helper, so it seems reasonable to me. I'm also not sure if this needs a test. I'll definitely add one on the cargo side if this is merged. Closes rust-lang#63329
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
The
--remap-path-prefixflag affects paths in dep-info files. This causes some problems witth Cargo.Cargo uses these paths to detect if any source file has been modified. Since the common use case for
--remap-path-prefixis to rewrite to some artificial path (like/rustc/$HASHwhich rust distributions use), this causes them to point to non-existent paths, which Cargo cannot check.In some cases, this doesn't matter. Workspace members are built with relative paths which (usually) won't match the remap value. However, registry or vendored paths will get remapped. Cargo won't find the path, so it will always assume it needs to rebuilt, breaking it's rebuild detection.
I think dep-info paths should not be remapped. I think it keeps with the spirit of reproducible builds (the binaries aren't affected, this is just a side-channel build-system file). However, I'm not certain. I also don't know how hard this will be to implement.
Oh, and
-Z binary-dep-depinfodoesn't seem to be affected by--remap-path-prefix.The text was updated successfully, but these errors were encountered: