Add stubs and heap region definitions (#13521)

* Add stubs and heap region definitions

* nudge

sdk/bpf/c/inc/solana_sdk.h

@@ -253,6 +253,20 @@ static void sol_free(void *ptr) {
   (void) sol_alloc_free_(0, ptr);
 }
 
+/**
+ * The Solana runtime provides a memory region that is available to programs at
+ * a fixed virtual address and length. The builtin functions `sol_calloc` and
+ * `sol_free` call into the Solana runtime to allocate from this memory region
+ * for heap operations.  Because the memory region is directly available to
+ * programs another option is a program can implement their own heap directly on
+ * top of that region.  If a program chooses to implement their own heap they
+ * should not call the builtin heap functions because they will conflict.
+ * `HEAP_START_ADDRESS` and `HEAP_LENGTH` specify the memory region's start
+ * virtual address and length.
+ */
+#define HEAP_START_ADDRESS (uint64_t)0x300000000
+#define HEAP_LENGTH (uint64_t)(32 * 1024)
+
 /**
  * Panics
  *
@@ -606,7 +620,7 @@ uint64_t entrypoint(const uint8_t *input);
 
 #ifdef SOL_TEST
 /**
- * Stub log functions when building tests
+ * Stub functions when building tests
  */
 #include <stdio.h>
 void sol_log_(const char *s, uint64_t len) {
@@ -625,6 +639,10 @@ void sol_log_pubkey(const SolPubkey *pubkey) {
 void sol_log_compute_units_() {
   printf("Program consumption: __ units remaining\n");
 }
+void sol_panic_(const char *file, uint64_t len, uint64_t line, uint64_t column) {
+  printf("Panic in %s at %d:%d\n", file, line, column);
+  abort();
+}
 #endif
 
 #ifdef __cplusplus