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diff --git a/docs/users_guide/packages.xml b/docs/users_guide/packages.xml
index ab4ab8d..b37e266 100644
--- a/docs/users_guide/packages.xml
+++ b/docs/users_guide/packages.xml
@@ -5,9 +5,12 @@ Packages
packages
- A package is a library of Haskell modules known to the compiler. GHC
- comes with several packages: see the accompanying
- library documentation.
+ A package is a library of Haskell modules known to the
+ compiler. GHC comes with several packages: see the accompanying
+ library
+ documentation. More packages to install can be obtained
+ from HackageDB.Using a package couldn't be simpler: if you're using
or GHCi, then most of the installed packages will be
@@ -74,24 +77,36 @@ exposed-modules: Network.BSD,
- This option causes the installed package P to be
- exposed. The package P can be specified
- in full with its version number
- (e.g. network-1.0) or the version number can be
- omitted if there is only one version of the package
- installed.
-
- If there are multiple versions of P
- installed, then all other versions will become hidden.
+ This option causes the installed
+ package P to be exposed. The
+ package P can be specified in
+ full with its version number
+ (e.g. network-1.0) or the version
+ number can be omitted if there is only one version of the
+ package installed. If there are multiple versions
+ of P installed, then all other
+ versions will become hidden.The
- option also causes package P to be
- linked into the resulting executable. In
- mode and GHCi, the compiler
- normally determines which packages are required by the current
- Haskell modules, and links only those. In batch mode however, the
- dependency information isn't available, and explicit
- options must be given when linking.
+ option also causes package P to
+ be linked into the resulting executable or shared
+ object. Whether a packages' library is linked statically
+ or dynamically is controlled by the flag
+ pair /.
+
+ In mode
+ and mode (see
+ ), the compiler normally
+ determines which packages are required by the current
+ Haskell modules, and links only those. In batch mode
+ however, the dependency information isn't available, and
+ explicit
+ options must be given when linking. The one other time you might need to use
+ to force linking a package is
+ when the package does not contain any Haskell modules (it
+ might contain a C library only, for example). In that
+ case, GHC will never discover a dependency on it, so it
+ has to be mentioned explicitly.For example, to link a program consisting of objects
Foo.o and Main.o, where
@@ -103,18 +118,7 @@ exposed-modules: Network.BSD,
The same flag is necessary even if we compiled the modules from
source, because GHC still reckons it's in batch mode:
-$ ghc -o myprog Foo.hs Main.hs -package network
-
- In --make and --interactive
- modes (), however, GHC figures out the
- packages required for linking without further assistance.
-
- The one other time you might need to use
- to force linking a package is when the
- package does not contain any Haskell modules (it might contain a C
- library only, for example). In that case, GHC
- will never discover a dependency on it, so it has to be mentioned
- explicitly.
+$ ghc -o myprog Foo.hs Main.hs -package network
@@ -345,65 +349,84 @@ $ export GHC_PACKAGE_PATH=$HOME/.my-ghc-packages.conf:
lot of configuration, then you might have to fall back to the low-level
mechanisms, so a few hints for those brave souls follow.
+ You need to build an "installed package info" file for
+ passing to ghc-pkg when installing your
+ package. The contents of this file are described in
+ .
+
+ The Haskell code in a package may be built into one or more
+ archive libraries (e.g. libHSfoo.a), or a
+ single shared object
+ (e.g. libHSfoo.dll/.so/.dylib). The
+ restriction to a single shared object is because the package
+ system is used to tell the compiler when it should make an
+ inter-shared-object call rather than an intra-shared-object-call
+ call (inter-shared-object calls require an extra
+ indirection).
-
- You need to build an "installed package info" file for
- passing to ghc-pkg when installing your
- package. The contents of this file are described in .
-
-
-
- The Haskell code in a package may be built into one or
- more archive libraries
- (e.g. libHSfoo.a), or a single DLL on
- Windows (e.g. HSfoo.dll). The
- restriction to a single DLL on Windows is because the
- package system is used to tell the compiler when it should
- make an inter-DLL call rather than an intra-DLL call
- (inter-DLL calls require an extra
- indirection). Building packages as DLLs doesn't
- work at the moment; see
- for the gory details.
-
-
- Building a static library is done by using the
+ Building a static library is done by using the
ar tool, like so:
-ar cqs libHSfoo.a A.o B.o C.o ...
+ar cqs libHSfoo-1.0.a A.o B.o C.o ...
- where A.o,
- B.o and so on are the compiled Haskell
- modules, and libHSfoo.a is the library
- you wish to create. The syntax may differ slightly on your
- system, so check the documentation if you run into
- difficulties.
-
- Versions of the Haskell libraries for use with GHCi
- may also be included: GHCi cannot load .a
- files directly, instead it will look for an object file
+ where A.o,
+ B.o and so on are the compiled Haskell
+ modules, and libHSfoo.a is the library you
+ wish to create. The syntax may differ slightly on your system,
+ so check the documentation if you run into difficulties.
+
+
+ Versions of the Haskell libraries for use with GHCi may also
+ abe included: GHCi cannot load .a files
+ directly, instead it will look for an object file
called HSfoo.o and load that. On some
- systems, the ghc-pkg tool can
- automatically build the GHCi version of each library, see
- . To build these
- libraries by hand from the .a archive, it
- is possible to use GNU ld as
- follows:
+ systems, the ghc-pkg tool can automatically
+ build the GHCi version of each library, see
+ . To build these libraries
+ by hand from the .a archive, it is possible
+ to use GNU ld as follows:ld -r ––whole-archive -o HSfoo.o libHSfoo.a(replace
- ––--whole-archive with
- –all_load on MacOS X)
-
- GHC does not maintain detailed cross-package
- dependency information. It does remember which modules in
- other packages the current module depends on, but not which
- things within those imported things.
+ ––whole-archive with
+ –all_load on MacOS X)
+
+
+ When building the package as shared object, GHC wraps
+ out the underlying linker so that the user gets a common
+ interface to all shared object variants that are supported
+ by GHC (DLLs, ELF DSOs, and Mac OS dylibs). The shared
+ object must be named in specific way for two reasons: (1)
+ the name must contain the GHC compiler version, so that two
+ library variants don't collide that are compiled by
+ different versions of GHC and that therefore are most likely
+ incompatible with respect to calling conventions, (2) it
+ must be different from the static name otherwise we would
+ not be able to control the linker as precisely as necessary
+ to make
+ the / flags
+ work, see .
+
+ghc -shared libHSfoo-1.0-ghcGHCVersion.so A.o B.o C.o
+ Using GHC's version number in the shared object name
+ allows different library versions compiled by different GHC
+ versions to be installed in standard system locations,
+ e.g. under *nix /usr/lib. To obtain the version number of
+ GHC invoke ghc --numeric-version and use
+ its output in place
+ of GHCVersion. See also
+ on how object files must
+ be prepared for shared object linking.
+
+ GHC does not maintain detailed cross-package dependency
+ information. It does remember which modules in other packages
+ the current module depends on, but not which things within
+ those imported things.
- To compile a module which is to be part of a new package,
+ To compile a module which is to be part of a new package,
use the -package-name option ().
Failure to use the -package-name option
when compiling a package will probably result in disaster, but
@@ -413,8 +436,8 @@ $ export GHC_PACKAGE_PATH=$HOME/.my-ghc-packages.conf:
same as the package name stored in the .hi
file.
- It is worth noting that on Windows, when each package
- is built as a DLL, since a reference to a DLL costs an extra
+ It is worth noting with shared objects, when each package
+ is built as a single shared object file, since a reference to a shared object costs an extra
indirection, intra-package references are cheaper than
inter-package references. Of course, this applies to the
main package as well.
@@ -446,6 +469,13 @@ $ export GHC_PACKAGE_PATH=$HOME/.my-ghc-packages.conf:
options are given, the rightmost one is used as the database to act
upon.
+ Commands that query the package database (list, latest,
+ describe, field) operate on the list of databases specified by
+ the flags , , and
+ . If none of these flags are
+ given, the default is
+ .
+
If the environment variable GHC_PACKAGE_PATH is
set, and its value does not end in a separator (: on
Unix, ; on Windows), then the last database is
@@ -506,6 +536,15 @@ $ export GHC_PACKAGE_PATH=$HOME/.my-ghc-packages.conf:
+ ghc-pkg check
+
+ Check consistency of dependencies in the package
+ database, and report packages that have missing
+ dependencies.
+
+
+
+ ghc-pkg hide PSets the exposed flag for package
@@ -608,7 +647,7 @@ $ export GHC_PACKAGE_PATH=$HOME/.my-ghc-packages.conf:
databases. Additionally, file will
also be the database modified by a register,
unregister, expose or
- hide command, unless it is overriden by a later
+ hide command, unless it is overridden by a later
, or
option.