Fix broken GC_release() for WASI

It was just using free() but it can be called in the middle of an allocation.

Instead, ignore shrink requests, since we can't do anything with them.

runtime/gc/heap.c

@@ -183,7 +183,9 @@ void shrinkHeap (GC_state s, GC_heap h, size_t keepSize) {
     }
     assert (isAligned (keepWithMapsSize, s->sysvals.pageSize));
     assert (keepWithMapsSize <= h->withMapsSize);
+#if HAS_SHRINK_HEAP
     GC_release (h->start + keepWithMapsSize, h->withMapsSize - keepWithMapsSize);
+#endif
     h->size = keepSize;
     h->withMapsSize = keepWithMapsSize;
   }

runtime/platform.h

@@ -35,6 +35,10 @@
 #error HAS_REMAP not defined
 #endif
 
+#ifndef HAS_SHRINK_HEAP
+#error HAS_SHRINK_HEAP not defined
+#endif
+
 #ifndef HAS_SIGALTSTACK
 #error HAS_SIGALTSTACK not defined
 #else

runtime/platform/aix.h

@@ -34,6 +34,7 @@
 #define HAS_MSG_DONTWAIT FALSE
 #define HAS_PTRACE FALSE
 #define HAS_REMAP FALSE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK TRUE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE

runtime/platform/cygwin.h

@@ -35,6 +35,7 @@
 
 #define HAS_FEROUND FALSE
 #define HAS_REMAP TRUE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK FALSE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN TRUE

runtime/platform/darwin.h

@@ -34,6 +34,7 @@
 #define HAS_FEROUND TRUE
 #define HAS_MSG_DONTWAIT TRUE
 #define HAS_REMAP FALSE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK TRUE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE

runtime/platform/freebsd.h

@@ -30,6 +30,7 @@
 #define HAS_FEROUND TRUE
 #define HAS_MSG_DONTWAIT TRUE
 #define HAS_REMAP FALSE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK TRUE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE

runtime/platform/hpux.h

@@ -52,6 +52,7 @@
 #define HAS_FEROUND TRUE
 #define HAS_MSG_DONTWAIT FALSE
 #define HAS_REMAP FALSE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK TRUE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE

runtime/platform/hurd.h

@@ -30,6 +30,7 @@
 #define HAS_FEROUND TRUE
 #define HAS_MSG_DONTWAIT TRUE
 #define HAS_REMAP TRUE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK TRUE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE

runtime/platform/linux.h

@@ -38,6 +38,7 @@
 #endif
 #define HAS_MSG_DONTWAIT TRUE
 #define HAS_REMAP TRUE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK TRUE
 #if (defined (__hppa__))
 #define NEEDS_SIGALTSTACK_EXEC TRUE

runtime/platform/mingw.h

@@ -33,6 +33,7 @@
 #define HAS_FEROUND FALSE
 #define HAS_MSG_DONTWAIT FALSE
 #define HAS_REMAP TRUE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK FALSE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN TRUE

runtime/platform/netbsd.h

@@ -30,6 +30,7 @@
 #define HAS_FEROUND FALSE
 #define HAS_MSG_DONTWAIT TRUE
 #define HAS_REMAP FALSE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK TRUE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE

runtime/platform/openbsd.h

@@ -30,6 +30,7 @@
 #define HAS_FEROUND FALSE
 #define HAS_MSG_DONTWAIT TRUE
 #define HAS_REMAP FALSE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK TRUE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE

runtime/platform/solaris.h

@@ -34,6 +34,7 @@
 #define HAS_FEROUND TRUE
 #define HAS_MSG_DONTWAIT TRUE
 #define HAS_REMAP FALSE
+#define HAS_SHRINK_HEAP TRUE
 #define HAS_SIGALTSTACK TRUE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE

runtime/platform/wasi.h

@@ -20,6 +20,7 @@
 #define HAS_FEROUND TRUE
 #define HAS_MSG_DONTWAIT TRUE
 #define HAS_REMAP FALSE
+#define HAS_SHRINK_HEAP FALSE
 #define HAS_SIGALTSTACK FALSE
 #define NEEDS_SIGALTSTACK_EXEC FALSE
 #define HAS_SPAWN FALSE