<Para>
<IndexTerm><Primary>-syslib <lib> option</Primary></IndexTerm>
If you are using a system-supplied non-Prelude library (e.g., the
-POSIX library), just use a <Option>-syslib posix</Option> option (for example). The
-right interface files should then be available. <XRef LinkEnd="ghc-prelude"> lists the
-libraries available by this mechanism.
+POSIX library), just use a <Option>-syslib posix</Option> option (for
+example). The right interface files should then be available. The
+accompanying HsLibs document lists the libraries available by this
+mechanism.
</Para>
</ListItem>
</VarListEntry>
<Title>The recompilation checker
</Title>
-<Para>
<IndexTerm><Primary>recompilation checker</Primary></IndexTerm>
-</Para>
<Para>
-In the olden days, GHC compared the newly-generated <Filename>.hi</Filename> file with
-the previous version; if they were identical, it left the old one
-alone and didn't change its modification date. In consequence,
-importers of a module with an unchanged output <Filename>.hi</Filename> file were not
+<variablelist>
+<VarListEntry>
+<Term><Option>-recomp</Option></Term>
+<IndexTerm><Primary><option>-recomp</option> option</Primary></IndexTerm>
+<ListItem>
+<Para>
+(On by default) Turn on recompilation checking. This will stop
+compilation early, leaving an existing <filename>.o</filename> file in
+place, if it can be determined that the module does not need to be
recompiled.
</Para>
+</ListItem>
+</VarListEntry>
+<VarListEntry>
+<Term><Option>-no-recomp</Option></Term>
+<IndexTerm><Primary><option>-recomp</option> option</Primary></IndexTerm>
+<ListItem>
+<Para>
+Turn off recompilation checking.
+</Para>
+</ListItem>
+</VarListEntry>
+</VariableList>
+</Para>
+
+<Para>
+In the olden days, GHC compared the newly-generated
+<Filename>.hi</Filename> file with the previous version; if they were
+identical, it left the old one alone and didn't change its
+modification date. In consequence, importers of a module with an
+unchanged output <Filename>.hi</Filename> file were not recompiled.
+</Para>
<Para>
-This doesn't work any more. In our earlier example, module <Literal>C</Literal> does
-not import module <Literal>A</Literal> directly, yet changes to <Filename>A.hi</Filename> should force a
-recompilation of <Literal>C</Literal>. And some changes to <Literal>A</Literal> (changing the
-definition of a function that appears in an inlining of a function
-exported by <Literal>B</Literal>, say) may conceivably not change <Filename>B.hi</Filename> one jot. So
+This doesn't work any more. In our earlier example, module
+<Literal>C</Literal> does not import module <Literal>A</Literal>
+directly, yet changes to <Filename>A.hi</Filename> should force a
+recompilation of <Literal>C</Literal>. And some changes to
+<Literal>A</Literal> (changing the definition of a function that
+appears in an inlining of a function exported by <Literal>B</Literal>,
+say) may conceivably not change <Filename>B.hi</Filename> one jot. So
now…
</Para>
signature within the interface file. It also keeps in every interface
file a list of the version numbers of everything it used when it last
compiled the file. If the source file's modification date is earlier
-than the <Filename>.o</Filename> file's date (i.e. the source hasn't changed since the
-file was last compiled), GHC will be clever. It compares the version
-numbers on the things it needs this time with the version numbers on
-the things it needed last time (gleaned from the interface file of the
-module being compiled); if they are all the same it stops compiling
-rather early in the process saying “Compilation IS NOT required”.
-What a beautiful sight!
-</Para>
-
-<Para>
-GHC <Emphasis>only</Emphasis> keeps detailed dependency information for “user” modules,
-not for “library” modules. It distinguishes the two by a hack: a module
-whose <Filename>.hi</Filename> file has an absolute path name is considered a library module,
-while a relative path name indicates a user module. So if you have a
-multi-directory application, use <Emphasis>relative</Emphasis> path names in your
-<Option>-i</Option> path, to force GHC to record detailed dependency information.
-Use absolute path names only for directories containing slowly-changing
+than the <Filename>.o</Filename> file's date (i.e. the source hasn't
+changed since the file was last compiled), and the
+<option>-recomp</option> is given on the command line, GHC will be
+clever. It compares the version numbers on the things it needs this
+time with the version numbers on the things it needed last time
+(gleaned from the interface file of the module being compiled); if
+they are all the same it stops compiling rather early in the process
+saying “Compilation IS NOT required”. What a beautiful
+sight!
+</Para>
+
+<Para>
+GHC <Emphasis>only</Emphasis> keeps detailed dependency information
+for “user” modules, not for “Prelude” modules.
+It distinguishes Prelude modules because their names start with
+"Prel", so don't start your modules that way!
+
+<!-- April 2000: hack disabled. Now we use a different hack!
+
+It distinguishes the two by a hack: a module whose
+<Filename>.hi</Filename> file has an absolute path name is considered
+a library module, while a relative path name indicates a user module.
+So if you have a multi-directory application, use
+<Emphasis>relative</Emphasis> path names in your <Option>-i</Option>
+path, to force GHC to record detailed dependency information. Use
+absolute path names only for directories containing slowly-changing
library modules.
</Para>
<Para>
-A path is considered “absolute” if it starts with “<Filename>/</Filename>”, or
-“<Filename>A:/</Filename>”, or “<Filename>A:\</Filename>” (or “<Filename>B:/</Filename>”, “<Filename>B:\</Filename>” etc).
+A path is considered “absolute” if it starts with
+“<Filename>/</Filename>”, or
+“<Filename>A:/</Filename>”, or
+“<Filename>A:\</Filename>” (or
+“<Filename>B:/</Filename>”,
+“<Filename>B:\</Filename>” etc).
</Para>
+-->
<Para>
Patrick Sansom had a workshop paper about how all this is done (though
-the details have changed quite a bit). <ULink URL="mailto:sansom@dcs.gla.ac.uk">Ask him</ULink>) if you want a copy.
+the details have changed quite a bit). <ULink URL="mailto:sansom@dcs.gla.ac.uk">Ask him</ULink> if you want a copy.
</Para>
</Sect2>
<VarListEntry>
<Term>No <Option>-O*</Option>-type option specified:</Term>
+<IndexTerm><Primary>-O* not specified</Primary></IndexTerm>
<ListItem>
<Para>
-<IndexTerm><Primary>-O* not specified</Primary></IndexTerm>
This is taken to mean: “Please compile quickly; I'm not over-bothered
about compiled-code quality.” So, for example: <Command>ghc -c Foo.hs</Command>
</Para>
</VarListEntry>
<VarListEntry>
<Term><Option>-O</Option> or <Option>-O1</Option>:</Term>
-<ListItem>
-<Para>
<IndexTerm><Primary>-O option</Primary></IndexTerm>
<IndexTerm><Primary>-O1 option</Primary></IndexTerm>
-<IndexTerm><Primary>optimise normally</Primary></IndexTerm>
-Means: “Generate good-quality code without taking too long about it.”
-Thus, for example: <Command>ghc -c -O Main.lhs</Command>
+<IndexTerm><Primary>optimise</Primary><secondary>normally</secondary></IndexTerm>
+<ListItem>
+<Para>
+Means: “Generate good-quality code without taking too long about
+it.” Thus, for example: <Command>ghc -c -O Main.lhs</Command>
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term><Option>-O2</Option>:</Term>
+<IndexTerm><Primary>-O2 option</Primary></IndexTerm>
+<IndexTerm><Primary>optimise</Primary><secondary>aggressively</secondary></IndexTerm>
<ListItem>
<Para>
-<IndexTerm><Primary>-O2 option</Primary></IndexTerm>
-<IndexTerm><Primary>optimise aggressively</Primary></IndexTerm>
Means: “Apply every non-dangerous optimisation, even if it means
significantly longer compile times.”
</Para>
</VarListEntry>
<VarListEntry>
<Term><Option>-O2-for-C</Option>:</Term>
-<ListItem>
-<Para>
<IndexTerm><Primary>-O2-for-C option</Primary></IndexTerm>
<IndexTerm><Primary>gcc, invoking with -O2</Primary></IndexTerm>
-</Para>
-
+<ListItem>
<Para>
Says to run GCC with <Option>-O2</Option>, which may be worth a few percent in
execution speed. Don't forget <Option>-fvia-C</Option>, lest you use the native-code
</VarListEntry>
<VarListEntry>
<Term><Option>-Onot</Option>:</Term>
-<ListItem>
-<Para>
<IndexTerm><Primary>-Onot option</Primary></IndexTerm>
<IndexTerm><Primary>optimising, reset</Primary></IndexTerm>
-</Para>
-
+<ListItem>
<Para>
-This option will make GHC “forget” any <Option>-O</Option>ish options it has seen so
-far. Sometimes useful; for example: <Command>make all EXTRA_HC_OPTS=-Onot</Command>.
+This option will make GHC “forget” any
+<Option>-O</Option>ish options it has seen so far. Sometimes useful;
+for example: <Command>make all
+EXTRA_HC_OPTS=-Onot</Command>.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term><Option>-Ofile <file></Option>:</Term>
-<ListItem>
-<Para>
<IndexTerm><Primary>-Ofile <file> option</Primary></IndexTerm>
<IndexTerm><Primary>optimising, customised</Primary></IndexTerm>
-</Para>
-
+<ListItem>
<Para>
-For those who need <Emphasis>absolute</Emphasis> control over <Emphasis>exactly</Emphasis>
-what options are used (e.g., compiler writers, sometimes :-), a list
-of options can be put in a file and then slurped in with <Option>-Ofile</Option>.
+For those who need <Emphasis>absolute</Emphasis> control over
+<Emphasis>exactly</Emphasis> what options are used (e.g., compiler
+writers, sometimes :-), a list of options can be put in a file and
+then slurped in with <Option>-Ofile</Option>.
</Para>
<Para>
-In that file, comments are of the <Literal>#</Literal>-to-end-of-line variety; blank
-lines and most whitespace is ignored.
+In that file, comments are of the
+<Literal>#</Literal>-to-end-of-line variety; blank lines and most
+whitespace is ignored.
</Para>
<Para>
GHC (as of version 4.00) supports Concurrent Haskell by default,
without requiring a special option or libraries compiled in a certain
way. To get access to the support libraries for Concurrent Haskell
-(i.e. <Literal>Concurrent</Literal> and friends), use the <Option>-syslib concurrent</Option> option.
+(i.e. <Literal>Concurrent</Literal> and friends), use the
+<Option>-syslib concurrent</Option> option.
</Para>
<Para>
Three RTS options are provided for modifying the behaviour of the
-threaded runtime system. See the descriptions of <Option>-C[<us>]</Option>, <Option>-q</Option>,
-and <Option>-t<num></Option> in <XRef LinkEnd="parallel-rts-opts">.
+threaded runtime system. See the descriptions of
+<Option>-C[<us>]</Option>, <Option>-q</Option>, and
+<Option>-t<num></Option> in <XRef LinkEnd="parallel-rts-opts">.
</Para>
<Para>
-Concurrent Haskell is described in more detail in <XRef LinkEnd="concurrent-and-parallel">.
+Concurrent Haskell is described in more detail in <XRef
+LinkEnd="sec-Concurrent">.
</Para>
</Sect1>
<Para>
To compile a Haskell program for parallel execution under PVM, use the
-<Option>-parallel</Option> option,<IndexTerm><Primary>-parallel option</Primary></IndexTerm> both when compiling
-<Emphasis>and linking</Emphasis>. You will probably want to <Literal>import Parallel</Literal>
-into your Haskell modules.
+<Option>-parallel</Option> option,<IndexTerm><Primary>-parallel
+option</Primary></IndexTerm> both when compiling <Emphasis>and
+linking</Emphasis>. You will probably want to <Literal>import
+Parallel</Literal> into your Haskell modules.
</Para>
<Para>
-To run your parallel program, once PVM is going, just invoke it “as
-normal”. The main extra RTS option is <Option>-N<n></Option>, to say how many
-PVM “processors” your program to run on. (For more details of
-all relevant RTS options, please see <XRef LinkEnd="parallel-rts-opts">.)
+To run your parallel program, once PVM is going, just invoke it
+“as normal”. The main extra RTS option is
+<Option>-N<n></Option>, to say how many PVM
+“processors” your program to run on. (For more details of
+all relevant RTS options, please see <XRef
+LinkEnd="parallel-rts-opts">.)
</Para>
<Para>
projects / ghc-hetmet.git / blobdiff