Monitor memory usage and panic on over 8MB used

libs/core/linux.cpp

@@ -13,14 +13,35 @@
 #include <sys/stat.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <malloc.h>
 
 #define THREAD_DBG(...)
 
+#define MALLOC_LIMIT (8 * 1024 * 1024)
+#define MALLOC_CHECK_PERIOD (1024 * 1024)
+
+void *xmalloc(size_t sz) {
+    static size_t allocBytes = 0;
+    allocBytes += sz;
+    if (allocBytes >= MALLOC_CHECK_PERIOD) {
+        allocBytes = 0;
+        auto info = mallinfo();
+        DMESG("malloc used: %d kb", info.uordblks / 1024);
+        if (info.uordblks > MALLOC_LIMIT) {
+            target_panic(904);
+        }
+    }
+    auto r = malloc(sz);
+    if (r == NULL)
+        target_panic(905); // shouldn't happen
+    return r;
+}
+
 void *operator new(size_t size) {
-    return malloc(size);
+    return xmalloc(size);
 }
 void *operator new[](size_t size) {
-    return malloc(size);
+    return xmalloc(size);
 }
 
 void operator delete(void *p) {

libs/core/png.cpp

@@ -88,7 +88,7 @@ Image unpackPNG(Buffer png) {
     uint32_t byteW = (hd.width + 7) >> 3;
     uint32_t expSize = (byteW + 1) * hd.height;
     unsigned long sz = expSize;
-    uint8_t *tmp = (uint8_t *)malloc(sz);
+    uint8_t *tmp = (uint8_t *)xmalloc(sz);
     int code = uncompress(tmp, &sz, png->data + sizeof(hd), hd.lenIDAT);
     if (code != 0) {
         DMESG("PNG: zlib failed: %d", code);

libs/core/pxt.h

@@ -3,6 +3,8 @@
 
 #include "pxtbase.h"
 
+void *xmalloc(size_t sz);
+
 namespace pxt {
 void raiseEvent(int id, int event);
 int allocateNotifyEvent();