Mps example code: hello-world with gc

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 Change: 159000
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mps/example/hw-gc/build

@@ -0,0 +1,4 @@
+CODE=../../code
+LIBS=$CODE/xcppgc/ci
+gcc  hwgc01.c -o hwgc01  -I$CODE $LIBS/mps.a $LIBS/mpsplan.a
+# ./a.out

mps/example/hw-gc/hwgc01.c

@@ -0,0 +1,107 @@
+/* Demo File: 05alloc.c */
+/* Simple C client of the MPS */
+
+#include <stdlib.h>  /* for malloc */
+#include <stdio.h>  /* for printf */
+#include <string.h>  /* for strcpy */
+
+#include "mps.h"
+#include "mpsacl.h"   /* for mps_arena_class_cl */
+#include "mpscmv.h"   /* for mps_class_mv */
+
+static void reportPoolmv(mps_pool_t Pool)
+{
+    size_t cbPoolFree = mps_mv_free_size(Pool);
+    printf(
+      "Pool has %lu bytes free.\n",
+      (unsigned long)cbPoolFree
+    );
+}
+
+int main(void)
+{
+  void *pBlock = NULL;
+  size_t cbBlock = 1024 * 1024;
+  mps_arena_t ArenaDemo = NULL;
+  mps_pool_t PoolDemo = NULL;
+
+  mps_res_t res;
+
+  {
+    /* Create arena */
+    
+    pBlock = malloc(cbBlock);
+    if(pBlock == NULL) {
+      printf("malloc failed!\n");
+      exit(1);
+    }
+
+    res = mps_arena_create(
+      &ArenaDemo,
+      mps_arena_class_cl(),
+      cbBlock,
+      pBlock
+    );
+    if (res != MPS_RES_OK) {
+      printf("mps_arena_create: failed with res %d.\n", res);
+      exit(2);
+    }
+  }
+  
+  {
+    /* Create pool */
+    
+    size_t cbPoolExtend = 1024;
+    size_t cbObjectAvg = 32;
+    size_t cbPoolMax = 64 * 1024;
+    
+    size_t cbPoolFree = 0;
+
+    res = mps_pool_create(
+      &PoolDemo,
+      ArenaDemo,
+      mps_class_mv(),
+      cbPoolExtend,
+      cbObjectAvg,
+      cbPoolMax
+    );
+    if (res != MPS_RES_OK) {
+      printf("mps_pool_create: failed with res %d.\n", res);
+      exit(2);
+    }
+    
+    reportPoolmv(PoolDemo);
+  }
+
+  {
+    /* Allocate memory */
+    
+    size_t cbBuffer = 100;
+    void *p = NULL;
+
+    res = mps_alloc(&p, PoolDemo, cbBuffer);
+    if (res != MPS_RES_OK) {
+      printf("mps_alloc: failed with res %d.\n", res);
+      exit(2);
+    }
+    
+    reportPoolmv(PoolDemo);
+
+    {
+      /* Show that it really is memory */
+
+      char *pbBuffer = (char *)p;
+      
+      strcpy(pbBuffer, "hello--world\n");
+      pbBuffer[5] = ',';
+      pbBuffer[6] = ' ';
+      printf(pbBuffer);
+    }
+  }
+
+  printf(
+    "Success: The hello-world example code successfully allocated\n"
+    "some memory using mps_alloc(), in an MV pool, in a CL arena.\n"
+  );
+  return 0;
+}