[Git][ghc/ghc][master] hadrian: Always canonicalize topDirectory

[Marge Bot (@marge-bot)]

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
5efa9ca5 by Ben Gamari at 2023-06-28T21:08:13-04:00
hadrian: Always canonicalize topDirectory

Hadrian's `topDirectory` is intended to provide an absolute path to the
root of the GHC tree. However, if the tree is reached via a symlink this

One question here is whether the `canonicalizePath` call is expensive
enough to warrant caching. In a quick microbenchmark I observed that
`canonicalizePath "."` takes around 10us per call; this seems
sufficiently low not to worry.

Alternatively, another approach here would have been to rather move the
canonicalization into `m4/fp_find_root.m4`. This would have avoided
repeated canonicalization but sadly path canonicalization is a hard
problem in POSIX shell.

Addresses #22451.

- - - - -


1 changed file:

- hadrian/src/Oracles/Setting.hs


Changes:

=====================================
hadrian/src/Oracles/Setting.hs
=====================================
@@ -17,6 +17,8 @@ module Oracles.Setting (
     ghcWithInterpreter
     ) where
 
+import System.Directory
+import System.Info.Extra
 import Hadrian.Expression
 import Hadrian.Oracles.TextFile
 import Hadrian.Oracles.Path
@@ -327,9 +329,14 @@ ghcCanonVersion = do
     let leadingZero = [ '0' | length ghcMinorVersion == 1 ]
     return $ ghcMajorVersion ++ leadingZero ++ ghcMinorVersion
 
--- | Path to the GHC source tree.
+-- | Absolute path to the GHC source tree.
 topDirectory :: Action FilePath
-topDirectory = fixAbsolutePathOnWindows =<< setting GhcSourcePath
+topDirectory = do
+    x <- fixAbsolutePathOnWindows =<< setting GhcSourcePath
+    canonicalize x
+  where
+    -- We must canonicalize as the source directory may be accessed via a symlink. See #22451.
+    canonicalize = if isWindows then return else liftIO . canonicalizePath
 
 ghcVersionStage :: Stage -> Action String
 ghcVersionStage (Stage0 {}) = setting GhcVersion



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5efa9ca545d8d33b9be4fc0ba91af1db38f19276

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5efa9ca545d8d33b9be4fc0ba91af1db38f19276
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