diff --git a/src/rvprof_internal.h b/src/rvprof_internal.h
index af6dde0..75d4971 100644
--- a/src/rvprof_internal.h
+++ b/src/rvprof_internal.h
@@ -30,7 +30,27 @@ typedef enum {
     RVPROF_ERROR_INVALID_STATE = -4,
     RVPROF_ERROR_STACK_OVERFLOW = -5,
     RVPROF_ERROR_STACK_UNDERFLOW = -6
-} rvprof_error_t
+} rvprof_error_t;
+
+// symbol table entry
+typedef struct{
+    uintptr_t addr;
+    char name[MAX_NAME_LEN];
+    size_t size;
+} symbol_entry_t;
+
+// region stack entry
+typedef struct {
+    char name[MAX_NAME_LEN];
+    uint64_t start_cycles;
+    uint64_t start_time_ns;
+    int depth;
+    int function_id;
+    int stack_id;
+    uint64_t child_time;
+    uint64_t child_cycles;
+    void* func_addr
+} region_t;
 
 
 #ifdef __cplusplus