Changes between Version 16 and Version 17 of Commentary/Libraries

Timestamp:

08/28/09 05:41:17 (4 years ago)

Author:

simonpj

Comment:

--

Commentary/Libraries

@@ -5 +5 @@
 The Boot Packages, along with the other subcomponents of the GHC build system, are in the file `packages` in a GHC tree. To get a list of them, you can run `make show VALUE=PACKAGES` in a configured GHC build tree.  (This variable is set in `$(TOP)/ghc.mk`.)
 
+You can see exactly which versions of what packages GHC depends on by looking in `$(TOP)/compiler/ghc.cabal.in`.
+
 Every installation of GHC includes the Boot Packages.
 
 == Zero-boot packages ==
 
-The '''Zero-boot Packages''' are a small subset of the boot packages.  Since GHC's source code imports the boot packages, ''even the bootstrap compiler must have the boot packages available''.  But for certain fast-moving boot packages (eg Cabal), we don't want to rely on the user having installed a bang-up-to-date version of the package.  So we begin the entire build process by installing the zero-boot packages in the bootstrap compiler.  (This installation is purely local to the build tree.)  The bootstrap compiler is expected to have all other (non-zero-) boot packages already installed.
+Since GHC's source code imports the boot packages, ''even the bootstrap compiler must have the boot packages available''.  (Or, more precisely, all the types and values that are imported must be available from some package in the bootstrap compiler; the exact set of packages does not need to be identical.)
+
+For the most part we simply assume that the bootstrap compiler already has the boot packages installed.  The '''Zero-boot Packages''' are a set of packages for which this assumption does not hold.  For example, for certain fast-moving boot packages (eg Cabal), we don't want to rely on the user having installed a bang-up-to-date version of the package.  
+
+So we begin the entire build process by installing the zero-boot packages in the bootstrap compiler.  (This installation is purely local to the build tree.)  
 
 As time goes on, a Zero-boot package may become an ordinary boot package, because the bootstrap compiler is expected to have (a sufficiently up to date) version of the package already.