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authorEelco Dolstra <eelco.dolstra@logicblox.com>2016-08-17T13·12+0200
committerEelco Dolstra <eelco.dolstra@logicblox.com>2016-08-17T15·19+0200
commit22d6e31fc6a9de2ee424984e629ccd2e394ba512 (patch)
tree0c8ea6b2799583edf3597f7723883ba4c1655c7e /src/libstore/derivations.cc
parentac841a46797a91eaddb3e0ad193c505fc49da597 (diff)
Add a mechanism for derivation attributes to reference the derivation's outputs
For example, you can now say:

  configureFlags = "--prefix=${placeholder "out"} --includedir=${placeholder "dev"}";

The strings returned by the ‘placeholder’ builtin are replaced at
build time by the actual store paths corresponding to the specified
outputs.

Previously, you had to work around the inability to self-reference by doing stuff like:

  preConfigure = ''
    configureFlags+=" --prefix $out --includedir=$dev"
  '';

or rely on ad-hoc variable interpolation semantics in Autoconf or Make
(e.g. --prefix=\$(out)), which doesn't always work.
Diffstat (limited to 'src/libstore/derivations.cc')
-rw-r--r--src/libstore/derivations.cc7
1 files changed, 7 insertions, 0 deletions
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index 7dcf71d468df..f051f10bd018 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -390,4 +390,11 @@ Sink & operator << (Sink & out, const BasicDerivation & drv)
 }
 
 
+std::string hashPlaceholder(const std::string & outputName)
+{
+    // FIXME: memoize?
+    return "/" + printHash32(hashString(htSHA256, "nix-output:" + outputName));
+}
+
+
 }