[m-rev.] diff: fix hlc.agc library build failure

[Fergus Henderson]

Estimated hours taken: 1
Branches: main

Fix a problem where the library wasn't building in grade `hlc.agc'
anymore after petdr's change to make io_stream a foreign_type.

compiler/ml_code_util.m:
	Don't abort for foreign_types if accurate GC is enabled; instead,
	just don't generate any GC code for them.  In other words, assume
	that foreign_types are not allowed to point to the Mercury heap.

doc/reference_manual.texi:
	Document that C foreign_types must not point to the Mercury heap.
	But leave this documentation commented out for now, since
	`--gc accurate' is not yet fully implemented or officially supported.

library/io.m:
	Add code to mercury_fclose() to explicitly deallocate the
	MercuryFile structure pointed to by the io_stream C foreign_type,
	when not using conservative GC.
	This avoids a potential memory leak in those grades.

Workspace: /home/ceres/fjh/mercury
Index: compiler/ml_code_util.m
===================================================================
RCS file: /home/mercury1/repository/mercury/compiler/ml_code_util.m,v
retrieving revision 1.63
diff -u -d -r1.63 ml_code_util.m
--- compiler/ml_code_util.m	7 May 2002 11:03:03 -0000	1.63
+++ compiler/ml_code_util.m	15 May 2002 07:34:54 -0000
@@ -2160,11 +2160,9 @@
 ml_type_might_contain_pointers(mlds__native_float_type) = no.
 ml_type_might_contain_pointers(mlds__native_bool_type) = no.
 ml_type_might_contain_pointers(mlds__native_char_type) = no.
-ml_type_might_contain_pointers(mlds__foreign_type(_)) = _ :-
-	sorry(this_file, "--gc accurate and foreign_type").
-	% It might contain pointers, so it's not safe to return `no',
-	% but it also might not be word-sized, so it's not safe to
-	% return `yes'.
+ml_type_might_contain_pointers(mlds__foreign_type(_)) = no.
+	% We assume that foreign types are not allowed to contain pointers
+	% to the Mercury heap.  XXX is this requirement too strict?
 ml_type_might_contain_pointers(mlds__class_type(_, _, Category)) =
 	(if Category = mlds__enum then no else yes).
 ml_type_might_contain_pointers(mlds__ptr_type(_)) = yes.
Index: doc/reference_manual.texi
===================================================================
RCS file: /home/mercury1/repository/mercury/doc/reference_manual.texi,v
retrieving revision 1.247
diff -u -d -r1.247 reference_manual.texi
--- doc/reference_manual.texi	7 May 2002 11:03:17 -0000	1.247
+++ doc/reference_manual.texi	15 May 2002 07:51:05 -0000
@@ -5503,6 +5503,11 @@
 at a later date we plan to lift this restriction and allow enum, struct
 and floating point types.
 
+ at c XXX No point documenting this until `--gc accurate'
+ at c     is officially supported.
+ at c With @samp{--gc accurate}, foreign_types which are C pointer types
+ at c must not point to the Mercury heap.
+
 If the @var{MercuryTypeName} is the type of a parameter of a procedure
 defined using @samp{pragma foreign_proc},
 it will be passed to the foreign_proc's foreign language code
Index: library/io.m
===================================================================
RCS file: /home/mercury1/repository/mercury/library/io.m,v
retrieving revision 1.253
diff -u -d -r1.253 io.m
--- library/io.m	12 May 2002 17:47:47 -0000	1.253
+++ library/io.m	15 May 2002 08:15:23 -0000
@@ -3848,6 +3848,18 @@
 
 #endif /* ! MR_NEW_MERCURYFILE_STRUCT */
 
+#ifndef MR_CONSERVATIVE_GC
+  		/*
+		** For the accurate GC or no GC cases,
+		** we need to explicitly deallocate the memory here,
+		** to avoid a memory leak.
+		** Note that the accurate collector won't reclaim
+		** io_streams, since the io__stream type is defined
+		** as a foreign_type.
+		*/
+  		MR_GC_FREE(mf);
+#endif /* !MR_CONSERVATIVE_GC */
+
 	}
 }
 
-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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