[lldb/Target] Slide source display for artificial locations at function start

lldb/source/Target/StackFrame.cpp

@@ -1892,14 +1892,33 @@ bool StackFrame::GetStatus(Stream &strm, bool show_frame_info, bool show_source,
       if (m_sc.comp_unit && m_sc.line_entry.IsValid()) {
         have_debuginfo = true;
         if (source_lines_before > 0 || source_lines_after > 0) {
+          uint32_t start_line = m_sc.line_entry.line;
+          if (!start_line && m_sc.function) {
+            FileSpec source_file;
+            m_sc.function->GetStartLineSourceInfo(source_file, start_line);
+          }
+
           size_t num_lines =
               target->GetSourceManager().DisplaySourceLinesWithLineNumbers(
-                  m_sc.line_entry.file, m_sc.line_entry.line,
-                  m_sc.line_entry.column, source_lines_before,
-                  source_lines_after, "->", &strm);
+                  m_sc.line_entry.file, start_line, m_sc.line_entry.column,
+                  source_lines_before, source_lines_after, "->", &strm);
           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("Warning: the current PC is an artificial location "
+                          "in function %s.",
+                          fn_name.AsCString());
+            else
+              strm.Printf(
+                  "Warning: the current PC is an artificial location "
+                  "but lldb couldn't associate it with a function in %s.",
+                  m_sc.line_entry.file.GetFilename().GetCString());
+            strm.EOL();
+          }
         }
       }
       switch (disasm_display) {

lldb/test/API/source-manager/TestSourceManager.py

@@ -204,7 +204,6 @@ def test_modify_source_file_while_debugging(self):
             SOURCE_DISPLAYED_CORRECTLY,
             substrs=['Hello world'])
 
-
         # The '-b' option shows the line table locations from the debug information
         # that indicates valid places to set source level breakpoints.
 
@@ -270,3 +269,19 @@ def test_set_breakpoint_with_absolute_path(self):
                     substrs=['stopped',
                              'main-copy.c:%d' % self.line,
                              'stop reason = breakpoint'])
+
+    def test_artificial_source_location(self):
+        src_file = 'artificial_location.c'
+        d = {'C_SOURCES': src_file }
+        self.build(dictionary=d)
+
+        lldbutil.run_to_source_breakpoint(
+            self, 'main',
+            lldb.SBFileSpec(src_file, False))
+
+        self.expect("run", RUN_SUCCEEDED,
+                    substrs=['stop reason = breakpoint', '%s:%d' % (src_file,0),
+                             'Warning: the current PC is an artificial ',
+                             'location in function '
+                             ])
+

lldb/test/API/source-manager/artificial_location.c

@@ -0,0 +1,6 @@
+int foo() { return 42; }
+
+int main() {
+#line 0
+  return foo();
+}