Derivation platform checking compares against wrong machine #30902
Comments
FRidh
added
the
6.topic: cross-compilation
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(tl;dr: 3 is the most important one re fixing the immediate issue.)
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… world First, we need check against the host platform, not the build platform. That's simple enough. Second, we move away from exahustive finite case analysis (i.e. exhaustively listing all platforms the package builds on). That only work in a closed-world setting, where we know all platforms we might build one. But with cross compilation, we may be building for arbitrary platforms, So we need fancier filters. This is the closed world to open world change. The solution is instead of having a list of systems (strings in the form "foo-bar"), we have a list of of systems or "patterns", i.e. attributes that partially match the output of the parsers in `lib.systems.parse`. The "check meta" logic treats the systems strings as an exact whitelist just as before, but treats the patterns as a fuzzy whitelist, intersecting the actual `hostPlatform` with the pattern and then checking for equality. (This is done using `matchAttrs`). The default convenience lists for `meta.platforms` are now changed to be lists of patterns (usually a single pattern) in `lib/systems/for-meta.nix` for maximum flexibility under this new system. Fixes NixOS#30902
… world First, we need check against the host platform, not the build platform. That's simple enough. Second, we move away from exahustive finite case analysis (i.e. exhaustively listing all platforms the package builds on). That only work in a closed-world setting, where we know all platforms we might build one. But with cross compilation, we may be building for arbitrary platforms, So we need fancier filters. This is the closed world to open world change. The solution is instead of having a list of systems (strings in the form "foo-bar"), we have a list of of systems or "patterns", i.e. attributes that partially match the output of the parsers in `lib.systems.parse`. The "check meta" logic treats the systems strings as an exact whitelist just as before, but treats the patterns as a fuzzy whitelist, intersecting the actual `hostPlatform` with the pattern and then checking for equality. (This is done using `matchAttrs`). The default convenience lists for `meta.platforms` are now changed to be lists of patterns (usually a single pattern) in `lib/systems/for-meta.nix` for maximum flexibility under this new system. Fixes #30902
Issue description
The logic in
pkgs/stdenv/generic/check-meta.nixfor checking themeta.platformsattribute currently comparesmeta.platformsagainst thestdenv.systemattribute. In my cross-compilation environmentstdenv.systemis the double of my build platform,x86_64-linux.It seems to me like this should rather be compared against
stdenv.hostPlatform.system. Unfortunately, this attribute has slightly different semantics thanstdenv.system. For instance, in the case ofarmv7l-hf-multiplatformit isarm-linuxwhereas the value expected byubootis something likearmv7l-linux.How much detail should
meta.systemcapture?Pinging @Ericson2314.
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