Add new garbage collector based on Julia

Use `--with-gc=julia` to switch to this alternative garbage
collector. There is also a new `--with-julia=` option which
can be used to point GAP at the correct Julia version (which
currently still needs some patches to add APIs we need).

The main work is in the new file src/julia_gc.c

GNUmakefile.in

@@ -61,6 +61,10 @@ READLINE_CPPFLAGS = @READLINE_CPPFLAGS@
 READLINE_LDFLAGS = @READLINE_LDFLAGS@
 READLINE_LIBS = @READLINE_LIBS@
 
+JULIA_CPPFLAGS = @JULIA_CPPFLAGS@
+JULIA_LDFLAGS = @JULIA_LDFLAGS@
+JULIA_LIBS = @JULIA_LIBS@
+
 BUILD_BOEHM_GC = @BUILD_BOEHM_GC@
 BOEHM_GC_CPPFLAGS = @BOEHM_GC_CPPFLAGS@
 BOEHM_GC_LDFLAGS = @BOEHM_GC_LDFLAGS@

Makefile.rules

@@ -151,11 +151,13 @@ GAP_PKG_CPPFLAGS += $(DEFS)
 # Add flags for dependencies
 GAP_CPPFLAGS += $(GMP_CPPFLAGS)
 GAP_CPPFLAGS += $(READLINE_CPPFLAGS)
+GAP_CPPFLAGS += $(JULIA_CPPFLAGS)
 GAP_CPPFLAGS += $(BOEHM_GC_CPPFLAGS)
 GAP_CPPFLAGS += $(LIBATOMIC_OPS_CPPFLAGS)
 
 GAP_PKG_CPPFLAGS += $(GMP_CPPFLAGS)
 GAP_PKG_CPPFLAGS += $(READLINE_CPPFLAGS)
+GAP_PKG_CPPFLAGS += $(JULIA_CPPFLAGS)
 GAP_PKG_CPPFLAGS += $(BOEHM_GC_CPPFLAGS)
 GAP_PKG_CPPFLAGS += $(LIBATOMIC_OPS_CPPFLAGS)
 
@@ -188,6 +190,7 @@ GAP_LDFLAGS = $(ABI_CFLAGS)
 # Add flags for dependencies
 GAP_LDFLAGS += $(GMP_LDFLAGS)
 GAP_LDFLAGS += $(READLINE_LDFLAGS)
+GAP_LDFLAGS += $(JULIA_LDFLAGS)
 GAP_LDFLAGS += $(BOEHM_GC_LDFLAGS)
 GAP_LDFLAGS += $(LIBATOMIC_OPS_LDFLAGS)
 
@@ -205,6 +208,7 @@ GAP_LIBS =
 # Add flags for dependencies
 GAP_LIBS += $(GMP_LIBS)
 GAP_LIBS += $(READLINE_LIBS)
+GAP_LIBS += $(JULIA_LIBS)
 GAP_LIBS += $(BOEHM_GC_LIBS)
 GAP_LIBS += $(LIBATOMIC_OPS_LIBS)
 

configure.ac

@@ -201,7 +201,7 @@ dnl
 dnl User setting: garbage collector to use
 dnl
 AC_ARG_WITH([gc],
-    [AS_HELP_STRING([--with-gc@<:@=default|gasman|boehm@:>@],
+    [AS_HELP_STRING([--with-gc@<:@=default|gasman|boehm|julia@:>@],
       [specify which garbage collector to use (default: gasman; for HPC-GAP: boehm)])],
     [],
     [with_gc=default])
@@ -223,7 +223,10 @@ AS_CASE([$with_gc],
                  AC_SUBST([GC_SOURCES], [src/gasman.c])
                  AC_DEFINE([USE_GASMAN],    [1], [define as 1 if GASMAN is used])
                 ],
-    [*],        [AC_MSG_ERROR([Invalid gc method '$with_gc', use default|none|gasman|boehm])],
+    [julia],    [AC_SUBST([GC_SOURCES], [src/julia_gc.c])
+                 AC_DEFINE([USE_JULIA_GC],  [1], [define as 1 if the Julia GC is used])
+                ],
+    [*],        [AC_MSG_ERROR([Invalid gc method '$with_gc', use default|none|gasman|boehm|julia])],
     )
 AC_MSG_RESULT([$with_gc])
 
@@ -389,6 +392,49 @@ AC_SUBST([READLINE_CPPFLAGS])
 AC_SUBST([READLINE_LDFLAGS])
 AC_SUBST([READLINE_LIBS])
 
+
+dnl Find julia
+AC_ARG_WITH([julia],
+  [AS_HELP_STRING([--with-julia@<:@=PREFIX@:>@],
+    [specify a prefix where julia can be found])])
+
+AS_IF([test "x$with_julia" != xno],[
+  JULIA_LIBS="-ljulia"
+  AS_CASE([x"$with_julia"],
+    [xyes|x],[
+      JULIA_CPPFLAGS=
+      JULIA_LDFLAGS=
+    ],
+    [*],[
+      JULIA_CPPFLAGS="-I$with_julia/include/julia"
+      JULIA_LDFLAGS="-L$with_julia/lib -Wl,-rpath,$with_julia/lib"
+      JULIA_LIBS="-ljulia"
+    ]
+  )
+
+  AX_CHECK_LIBRARY([JULIA], [julia.h], [julia], [jl_gc_alloc], [], [], [])
+
+  # TODO: also check for gcext.h, so that we can be sure the user is pointing
+  # at a modified version of Julia.
+
+  AS_IF([test $ax_cv_have_JULIA = yes],[
+    AC_DEFINE([HAVE_LIBJULIA], [1], [Define if you have libjulia])
+  ],[
+    AS_CASE([x"$with_julia"],
+      [x], [JULIA_CPPFLAGS= JULIA_LDFLAGS= JULIA_LIBS=],
+      [*], [AC_MSG_FAILURE([--with-julia was given, but test for julia failed])]
+    )
+  ])
+])
+
+dnl TODO: check if $with_gc = julia; if so, error out if julia is not found
+
+
+AC_SUBST([JULIA_CPPFLAGS])
+AC_SUBST([JULIA_LDFLAGS])
+AC_SUBST([JULIA_LIBS])
+
+
 dnl Find ward (if HPC-GAP mode is enabled)
 AC_ARG_WITH([ward],
   [AS_HELP_STRING([--with-ward@<:@=PREFIX@:>@],

src/gasman.h

@@ -338,10 +338,20 @@ static inline void SET_PTR_BAG(Bag bag, Bag *val)
 
 #if !defined(USE_GASMAN)
 
+#ifndef USE_JULIA_GC
+
 static inline void CHANGED_BAG(Bag bag)
 {
 }
 
+#else
+
+// Julia
+//
+void CHANGED_BAG(Bag bag);
+
+#endif
+
 #elif defined(MEMORY_CANARY)
 
 /****************************************************************************
@@ -822,10 +832,10 @@ extern void MarkAllButFirstSubBags( Bag bag );
 **  identifier.
 
 */
-#ifdef USE_GASMAN
-extern void MarkBag( Bag bag );
-#else
+#ifdef USE_BOEHM_GC
 static inline void MarkBag( Bag bag ) {}
+#else
+extern void MarkBag( Bag bag );
 #endif
 
 
@@ -889,6 +899,13 @@ extern  Bag *                   AllocBags;
 #define FORGET_WP(loc) \
 	GC_unregister_disappearing_link((void **)(loc))
 
+#else
+
+#define IS_WEAK_DEAD_BAG(bag) (0)
+
+#define REGISTER_WP(loc, obj) ((void) 0)
+#define FORGET_WP(loc) ((void) 0)
+
 #endif
 
 /****************************************************************************