[m-rev.] For review: New FAQ entries for installation.

[Paul Bone]

For review by anyone.

Estimated hours taken: 0.5
Branches: main
	
Add a new FAQ section 'installation', and create two questions within it.

The first question describes a work-around for bugs 66 and 77.

The second question describes why the make install process takes a while and
directs the user to the Grades section in the User Guide.

doc/faq.texi:
	As above.


Index: doc/faq.texi
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/doc/faq.texi,v
retrieving revision 1.33
diff -u -p -r1.33 faq.texi
--- doc/faq.texi	14 Jan 2008 00:08:01 -0000	1.33
+++ doc/faq.texi	20 Aug 2008 02:03:20 -0000
@@ -75,12 +75,54 @@ into another language, under the above c
 @node Top,,, (mercury)
 @top The Mercury Frequently Asked Questions List, version <VERSION>
 @menu
+* Installing::      Problems during compilation and installation.
 * Programming::     Common programming errors.
 * Unimplemented::   Problems caused by unimplemented Mercury features.
 * Last resort::     What to do when all else fails.
 @end menu
 @end ifnottex
 
+ at node Installing
+ at chapter Problems during compilation and installation.
+
+ at enumerate
+
+ at item
+ at emph{The compiler crashes during the ``make install'' phase}
+ at sp 1
+
+An incompatibility between Mercury's low-level C backend and some GCC
+optimizations in GCC 4.2 seems to be causing problems.  Try using a different
+version of GCC, otherwise the following instructions may help.
+
+After unpacking the tarball but before running @samp{configure}, create a file in
+the root directory of the unpacked source named @samp{Mmake.params} containing
+the line @samp{-EXTRA_CFLAGS=-O0}, and run @samp{configure} as
+ at samp{./configure --with-llds-base-grade=none --with-default-grade=hlc.gc}.
+This disables GCC's optimizations and some of Mercury's optimizations for the
+low-level C backend.  Programs build using this Mercury installation will use
+the high-level C backend by default.
+
+See bugs 66 and 77.
+
+ at sp 1
+ at item
+ at emph{The ``make install'' phase takes ages!  What's going on?}
+ at sp 1
+
+Mercury supports many grades, a grade is a combination the target language and
+feature options.  These features include garbage collection, debugging and
+profiling support.  See ``Grades and grade components'' in the User's Guide.
+
+During the ``make install'' phase the newly built compiler is used to compile
+the standard library in each of the selected grades, the runtime system is also
+rebuild for each grade. 
+
+To install fewer grades and reduce the time ``make install'' takes, see the
+configure script's options, in particular @samp{--disable-most-grades}.
+
+ at end enumerate
+
 @node Programming
 @chapter Common programming errors
 
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