Extract behavior in own function.

Author: ZeroIntensity

Python/traceback.c

@@ -1104,14 +1104,34 @@ _Py_DumpTracebackThreads(int fd, PyInterpreterState *interp,
     return NULL;
 }
 
+#define TRACEBACK_ENTRY_MAX_SIZE 256
+
+static void
+format_entry(char *entry_str, const char *the_entry, Py_ssize_t *length_ptr)
+{
+    int length = PyOS_snprintf(entry_str, TRACEBACK_ENTRY_MAX_SIZE, "  %s\n", the_entry);
+    if (length == TRACEBACK_ENTRY_MAX_SIZE) {
+        /* We exceeded the size, make it look prettier */
+        // Add ellipsis to last 3 characters
+        entry_str[TRACEBACK_ENTRY_MAX_SIZE - 5] = '.';
+        entry_str[TRACEBACK_ENTRY_MAX_SIZE - 4] = '.';
+        entry_str[TRACEBACK_ENTRY_MAX_SIZE - 3] = '.';
+        // Ensure trailing newline
+        entry_str[TRACEBACK_ENTRY_MAX_SIZE - 2] = '\n';
+        // Ensure that it's null-terminated
+        entry_str[TRACEBACK_ENTRY_MAX_SIZE - 1] = '\0';
+    }
+
+    *length_ptr = (Py_ssize_t)length;
+}
+
 /* This is for faulthandler.
  * Apparently, backtrace() doesn't play well across DLL boundaries on macOS */
 #if defined(HAVE_EXECINFO_H) && defined(HAVE_BACKTRACE) && defined(HAVE_BACKTRACE_SYMBOLS)
 void
 _Py_DumpStack(int fd)
 {
 #define BACKTRACE_SIZE 32
-#define TRACEBACK_ENTRY_MAX_SIZE 256
     PUTS(fd, "Current thread's C stack trace (most recent call first):\n");
     void *callstack[BACKTRACE_SIZE];
     int frames = backtrace(callstack, BACKTRACE_SIZE);
@@ -1128,19 +1148,8 @@ _Py_DumpStack(int fd)
     }
     for (int i = 0; i < frames; ++i) {
         char entry_str[TRACEBACK_ENTRY_MAX_SIZE];
-        snprintf(entry_str, TRACEBACK_ENTRY_MAX_SIZE, "  %s\n", strings[i]);
-        size_t length = strlen(entry_str) + 1;
-        if (length == TRACEBACK_ENTRY_MAX_SIZE) {
-            /* We exceeded the size, make it look prettier */
-            // Add ellipsis to last 3 characters
-            entry_str[TRACEBACK_ENTRY_MAX_SIZE - 5] = '.';
-            entry_str[TRACEBACK_ENTRY_MAX_SIZE - 4] = '.';
-            entry_str[TRACEBACK_ENTRY_MAX_SIZE - 3] = '.';
-            // Ensure trailing newline
-            entry_str[TRACEBACK_ENTRY_MAX_SIZE - 2] = '\n';
-            // Ensure that it's null-terminated
-            entry_str[TRACEBACK_ENTRY_MAX_SIZE - 1] = '\0';
-        }
+        Py_ssize_t length;
+        format_entry(entry_str, strings[i], &length);
         _Py_write_noraise(fd, entry_str, length);
     }