fix dead recursion when __NATIVE_USE_KLIB__ is defined

am/src/native/trm.c

@@ -1,5 +1,6 @@
 #include <am.h>
 #include <stdio.h>
+#include <klib-macros.h>
 
 void __am_platform_dummy();
 void __am_exit_platform(int code);
@@ -13,9 +14,16 @@ void putch(char ch) {
 }
 
 void halt(int code) {
-  printf("Exit (%d)\n", code);
+  const char *fmt = "Exit code = 40h\n";
+  for (const char *p = fmt; *p; p++) {
+    char ch = *p;
+    if (ch == '0' || ch == '4') {
+      ch = "0123456789abcdef"[(code >> (ch - '0')) & 0xf];
+    }
+    putch(ch);
+  }
   __am_exit_platform(code);
-  printf("Should not reach here!\n");
+  putstr("Should not reach here!\n");
   while (1);
 }
 

klib/src/stdlib.c

@@ -30,7 +30,13 @@ int atoi(const char* nptr) {
 }
 
 void *malloc(size_t size) {
+  // On native, malloc() will be called during initializaion of C runtime.
+  // Therefore do not call panic() here, else it will yield a dead recursion:
+  //   panic() -> putchar() -> (glibc) -> malloc() -> panic()
+#if !(defined(__ISA_NATIVE__) && defined(__NATIVE_USE_KLIB__))
   panic("Not implemented");
+#endif
+  return NULL;
 }
 
 void free(void *ptr) {