From 30875fa698e2ffed536f7a7d15a430e69a6a28ba Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Wed, 17 Jul 2024 17:36:25 -0700
Subject: [PATCH] libbacktrace: better backtrace_print when no debug info

Fixes https://github.com/ianlancetaylor/libbacktrace/issues/59

	* print.c (print_syminfo_callback): New static function.
	(print_callback): Call backtrace_syminfo if there is no function
	or file name.
---
 libbacktrace/print.c | 57 +++++++++++++++++++++++++++++++-------------
 1 file changed, 41 insertions(+), 16 deletions(-)

diff --git a/libbacktrace/print.c b/libbacktrace/print.c
index 3e61f02ebbc..70f5a93c49d 100644
--- a/libbacktrace/print.c
+++ b/libbacktrace/print.c
@@ -47,22 +47,6 @@ struct print_data
   FILE *f;
 };
 
-/* Print one level of a backtrace.  */
-
-static int
-print_callback (void *data, uintptr_t pc, const char *filename, int lineno,
-		const char *function)
-{
-  struct print_data *pdata = (struct print_data *) data;
-
-  fprintf (pdata->f, "0x%lx %s\n\t%s:%d\n",
-	   (unsigned long) pc,
-	   function == NULL ? "???" : function,
-	   filename == NULL ? "???" : filename,
-	   lineno);
-  return 0;
-}
-
 /* Print errors to stderr.  */
 
 static void
@@ -78,6 +62,47 @@ error_callback (void *data, const char *msg, int errnum)
   fputc ('\n', stderr);
 }
 
+/* Print one level of a backtrace if we couldn't get a file or function name.
+   Use syminfo to try to get a symbol name.  */
+
+static void print_syminfo_callback (void *data, uintptr_t pc,
+				    const char *symname, uintptr_t symval,
+				    uintptr_t symsize ATTRIBUTE_UNUSED)
+{
+  struct print_data *pdata = (struct print_data *) data;
+
+  if (symname == NULL)
+    fprintf (pdata->f, "0x%lx ???\n\t???:0\n", (unsigned long) pc);
+  else
+    fprintf (pdata->f, "0x%lx ???\n\t%s+0x%lx:0\n",
+	     (unsigned long) pc,
+	     symname,
+	     pc - symval);
+}
+
+/* Print one level of a backtrace.  */
+
+static int
+print_callback (void *data, uintptr_t pc, const char *filename, int lineno,
+		const char *function)
+{
+  struct print_data *pdata = (struct print_data *) data;
+
+  if (function == NULL && filename == NULL)
+    {
+      backtrace_syminfo (pdata->state, pc, print_syminfo_callback,
+			 error_callback, data);
+      return 0;
+    }
+
+  fprintf (pdata->f, "0x%lx %s\n\t%s:%d\n",
+	   (unsigned long) pc,
+	   function == NULL ? "???" : function,
+	   filename == NULL ? "???" : filename,
+	   lineno);
+  return 0;
+}
+
 /* Print a backtrace.  */
 
 void __attribute__((noinline))