[Lldb-commits] [lldb] [lldb] Reword the "line 0" warning (PR #116827)

[Pavel Labath via lldb-commits]

https://github.com/labath created https://github.com/llvm/llvm-project/pull/116827

We got a bug report that this message is confusing.  In this particular case, the line zero was due to compiler tail merging (in optimized code). The main issue was the "no source code" part: in this case it's kind of incorrect because -- even though we can't really know that -- the address is arguably associated with *multiple* lines of source code.

I've tried to make the new wording more neutral, and added a wink towards compiler optimizations. I left out the "compiler generated" part of the message because I couldn't find a way to squeeze that in nicely. I'm also not entirely sure what it was referring to -- if this was (just) function prologue/epilogue, then maybe leaving it out is fine, as we're not likely to stop there anyway (?)

I also left out the function name, because:
- for template functions it gets rather long
- it's already present in the message, potentially twice (once in the "frame summary" line and once in the snippet of code we show for the function declaration)

>From 59f306aed0736a861f5d084f6e203337234bfb96 Mon Sep 17 00:00:00 2001
From: Pavel Labath <pavel at labath.sk>
Date: Tue, 19 Nov 2024 17:03:48 +0100
Subject: [PATCH] [lldb] Reword the "line 0" warning

We got a bug report that this message is confusing.  In this particular
case, the line zero was due to compiler tail merging (in optimized
code). The main issue was the "no source code" part: in this case it's
kind of incorrect because -- even though we can't really know that --
the address is arguably associated with *multiple* lines of source code.

I've tried to make the new wording more neutral, and added a wink
towards compiler optimizations. I left out the "compiler generated" part
of the message because I couldn't find a way to squeeze that in nicely.
I'm also not entirely sure what it was referring to -- if this was
(just) function prologue/epilogue, then maybe leaving it out is fine, as
we're not likely to stop there anyway (?)

I also left out the function name, because:
- for template functions it gets rather long
- it's already present in the message, potentially twice (once in the
  "frame summary" line and once in the snippet of code we show for the
  function declaration)
---
 lldb/source/Target/StackFrame.cpp                | 16 +++-------------
 .../test/API/source-manager/TestSourceManager.py |  4 ++--
 2 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/lldb/source/Target/StackFrame.cpp b/lldb/source/Target/StackFrame.cpp
index 1bca9786fb7c70..ece85a077385ed 100644
--- a/lldb/source/Target/StackFrame.cpp
+++ b/lldb/source/Target/StackFrame.cpp
@@ -2007,19 +2007,9 @@ bool StackFrame::GetStatus(Stream &strm, bool show_frame_info, bool show_source,
           if (num_lines != 0)
             have_source = true;
           // TODO: Give here a one time warning if source file is missing.
-          if (!m_sc.line_entry.line) {
-            ConstString fn_name = m_sc.GetFunctionName();
-
-            if (!fn_name.IsEmpty())
-              strm.Printf(
-                  "Note: this address is compiler-generated code in function "
-                  "%s that has no source code associated with it.",
-                  fn_name.AsCString());
-            else
-              strm.Printf("Note: this address is compiler-generated code that "
-                          "has no source code associated with it.");
-            strm.EOL();
-          }
+          if (!m_sc.line_entry.line)
+            strm << "Note: This address is not associated with a specific line "
+                    "of code. This may be due to compiler optimizations.\n";
         }
       }
       switch (disasm_display) {
diff --git a/lldb/test/API/source-manager/TestSourceManager.py b/lldb/test/API/source-manager/TestSourceManager.py
index 7071f094e20f7e..ca415626f0d74c 100644
--- a/lldb/test/API/source-manager/TestSourceManager.py
+++ b/lldb/test/API/source-manager/TestSourceManager.py
@@ -336,8 +336,8 @@ def test_artificial_source_location(self):
                 "stop reason = breakpoint",
                 f"{src_file}:0",
                 "static int foo();",
-                "Note: this address is compiler-generated code in function",
-                "that has no source code associated with it.",
+                "Note: This address is not associated with a specific line "
+                "of code. This may be due to compiler optimizations."
             ],
         )