X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fusing.xml;h=ce7ef7680b2f174ce1cd8f478a42289a1b9481b6;hb=aedb94f5f220b5e442b23ecc445fd38c8d9b6ba0;hp=60b8f3effc75eefcf6151deda88f78d1dcd6ac6c;hpb=949ce3bb4ef2654a814b3549051e439daf82b5e9;p=ghc-hetmet.git
diff --git a/docs/users_guide/using.xml b/docs/users_guide/using.xml
index 60b8f3e..ce7ef76 100644
--- a/docs/users_guide/using.xml
+++ b/docs/users_guide/using.xml
@@ -841,11 +841,13 @@ ghc -c Foo.hs
of warnings which are generally likely to indicate bugs in your
program. These are:
,
- ,
+ ,
,
,
- , and
- . The following flags are
+ ,
+ , and
+ . The following
+ flags are
simple ways to select standard “packages” of warnings:
@@ -917,15 +919,16 @@ ghc -c Foo.hs
- :
+ :
-
+
+ warningsdeprecations
- Causes a warning to be emitted when a deprecated
- function or type is used. Entities can be marked as
- deprecated using a pragma, see .
+ Causes a warning to be emitted when a
+ module, function or type with a WARNING or DEPRECATED pragma
+ is used. See for more
+ details on the pragmas.This option is on by default.
@@ -945,6 +948,30 @@ ghc -c Foo.hs
+ :
+
+
+
+ Causes a warning to be emitted for foreign imports of
+ the following form:
+
+foreign import "f" f :: FunPtr t
+
+ on the grounds that it probably should be
+
+foreign import "&f" f :: FunPtr t
+
+ The first form declares that `f` is a (pure) C
+ function that takes no arguments and returns a pointer to a
+ C function with type `t`, whereas the second form declares
+ that `f` itself is a C function with type `t`. The first
+ declaration is usually a mistake, and one that is hard to
+ debug because it results in a crash, hence this
+ warning.
+
+
+
+ :
@@ -1152,7 +1179,8 @@ f foo = foo { x = 6 }
The trouble with orphans is that GHC must pro-actively read the interface
files for all orphan modules, just in case their instances or rules
play a role, whether or not the module's interface would otherwise
- be of any use. Other things being equal, avoid orphan modules.
+ be of any use. See for details.
+
@@ -1738,7 +1766,7 @@ f "2" = 2
parallelism.
- Options to enable SMP parallelism
+ Options for SMP parallelismIn order to make use of multiple CPUs, your program must be
linked with the option (see RTS option
Use x simultaneous threads when
running the program. Normally x
- should be chosen to match the number of CPU cores on the machine.
- There is no means (currently) by which this value may vary after
- the program has started.
-
- For example, on a dual-core machine we would probably use
+ should be chosen to match the number of CPU cores on the
+ machineWhether hyperthreading cores should be counted or not is an
+ open question; please feel free to experiment and let us know what
+ results you find.. For example,
+ on a dual-core machine we would probably use
+RTS -N2 -RTS.
- Whether hyperthreading cores should be counted or not is an
- open question; please feel free to experiment and let us know what
- results you find.
+ Setting also has the effect of
+ setting (the number of OS threads to
+ use for garbage collection) to the same value.
+
+ There is no means (currently) by which this value
+ may vary after the program has started.
+
+ The following options affect the way the runtime schedules
+ threads on CPUs:
+
+
+
+
+ RTS
+ option
+
+ Disable automatic migration for load balancing.
+ Normally the runtime will automatically try to schedule
+ threads across the available CPUs to make use of idle
+ CPUs; this option disables that behaviour. It is probably
+ only of use if you are explicitly scheduling threads onto
+ CPUs with GHC.Conc.forkOnIO.
+
+
+
+
+ RTS
+ option
+
+ Migrate a thread to the current CPU when it is woken
+ up. Normally when a thread is woken up after being
+ blocked it will be scheduled on the CPU it was running on
+ last; this option allows the thread to immediately migrate
+ to the CPU that unblocked it.
+
+ The rationale for allowing this eager migration is
+ that it tends to move threads that are communicating with
+ each other onto the same CPU; however there are
+ pathalogical situations where it turns out to be a poor
+ strategy. Depending on the communication pattern in your
+ program, it may or may not be a good idea.
+
+
+
@@ -1837,7 +1906,7 @@ statements or clauses.
GHC can dump its optimized intermediate code (said to be in “Core” format)
to a file as a side-effect of compilation. Non-GHC back-end tools can read and process Core files; these files have the suffix
- .hcr. The Core format is described in
+ .hcr. The Core format is described in An External Representation for the GHC Core Language,
and sample tools
for manipulating Core files (in Haskell) are in the GHC source distribution