backtrace.c: add macros for clarity

src/backtrace.c

@@ -17,6 +17,10 @@
 #include <mruby/internal.h>
 #include <mruby/presym.h>
 
+#define MAX_IREP_REFCNT UINT16_MAX
+#define UNKNOWN_LINENO -1
+#define UNKNOWN_LOCATION "(unknown):0"
+
 static void
 copy_backtrace(mrb_state *mrb,
                  const struct mrb_backtrace_location *loc,
@@ -25,7 +29,7 @@ copy_backtrace(mrb_state *mrb,
 {
   ptr[n] = *loc;
   if (loc->irep) {
-    if (loc->irep->refcnt == UINT16_MAX) {
+    if (loc->irep->refcnt == MAX_IREP_REFCNT) {
       ptr[n].irep = NULL;
     }
     else {
@@ -34,6 +38,16 @@ copy_backtrace(mrb_state *mrb,
   }
 }
 
+/**
+ * Creates a packed backtrace from the current call stack
+ *
+ * @param mrb The mruby state
+ * @param ciidx The current callinfo index
+ * @param ptr Pointer to store the backtrace locations
+ * @return Number of backtrace entries
+ * @note This function handles both proc and non-proc cases, managing IREP references
+ *       and building location entries for each stack frame.
+ */
 static size_t
 pack_backtrace(mrb_state *mrb, ptrdiff_t ciidx, struct mrb_backtrace_location *ptr)
 {
@@ -129,19 +143,30 @@ decode_location(mrb_state *mrb, const struct mrb_backtrace_location *entry)
   int32_t lineno;
   const char *filename;
 
-  if (!entry->irep || !mrb_debug_get_position(mrb, entry->irep, entry->idx, &lineno, &filename)) {
-    btline = mrb_str_new_lit(mrb, "(unknown):0");
+  // Case 1: No IREP or debug info available
+  if (!entry->irep) {
+    return mrb_str_new_lit(mrb, UNKNOWN_LOCATION);
   }
-  else if (lineno != -1) {//debug info was available
+
+  // Case 2: Debug info lookup failed
+  if (!mrb_debug_get_position(mrb, entry->irep, entry->idx, &lineno, &filename)) {
+    return mrb_str_new_lit(mrb, UNKNOWN_LOCATION);
+  }
+
+  // Case 3: Valid debug info
+  if (lineno != UNKNOWN_LINENO) {
     btline = mrb_format(mrb, "%s:%d", filename, (int)lineno);
   }
   else { //all that was left was the stack frame
     btline = mrb_format(mrb, "%s:0", filename);
   }
+
+  // Add method name if available
   if (entry->method_id != 0) {
     mrb_str_cat_lit(mrb, btline, ":in ");
     mrb_str_cat_cstr(mrb, btline, mrb_sym_name(mrb, entry->method_id));
   }
+
   return btline;
 }
 
@@ -233,7 +258,7 @@ print_backtrace(mrb_state *mrb, struct RObject *exc, struct RBasic *ptr)
     }
   }
   else {
-    fputs("(unknown):0: ", stderr);
+    fputs(UNKNOWN_LOCATION ": ", stderr);
   }
 
   if (exc == mrb->nomem_err) {