[Lldb-commits] [PATCH] D50304: [lldb] CommandObjectThreadUntil should set breakpoint at either on exact or the nearest subsequent line number but not on all the subsequent line numbers

[Venkata Ramanaiah Nalamothu via Phabricator via lldb-commits]

ramana-nvr created this revision.
ramana-nvr added a reviewer: jingham.

The requirements for "thread until <line number>" are:

a) If any code contributed by <line number> or the nearest subsequent of <line number> is executed before leaving the function, stop
b) If you end up leaving the function w/o triggering (a), then stop

In case of (a), since the <line number> may have multiple entries in the line table and the compiler might have scheduled/moved the relevant code across, and the lldb does not know the control flow, set breakpoints on all the line table entries of best match of <line number> i.e. exact or the nearest subsequent line.

Along with the above, currently, CommandObjectThreadUntil is also setting the breakpoints on all the subsequent line numbers after the best match and this latter part is wrong.

This issue is discussed at http://lists.llvm.org/pipermail/lldb-dev/2018-August/013979.html.


https://reviews.llvm.org/D50304

Files:
  source/Commands/CommandObjectThread.cpp


Index: source/Commands/CommandObjectThread.cpp
===================================================================
--- source/Commands/CommandObjectThread.cpp
+++ source/Commands/CommandObjectThread.cpp
@@ -1227,11 +1227,26 @@
         line_table->FindLineEntryByAddress(fun_end_addr, function_start,
                                            &end_ptr);
 
+        // Since not all source lines will contribute code, check if we are
+        // setting the breakpoint on the exact line number or the nearest
+        // subsequent line number and then set breakpoints at all the line
+        // entries of the chosen line number (exact or nearest subsequent).
         for (uint32_t line_number : line_numbers) {
+          LineEntry line_entry;
+          bool exact = true;
           uint32_t start_idx_ptr = index_ptr;
+          start_idx_ptr = sc.comp_unit->FindLineEntry(
+              index_ptr, line_number, sc.comp_unit, exact, &line_entry);
+          if (start_idx_ptr == UINT32_MAX) {
+            exact = false;
+            start_idx_ptr = sc.comp_unit->FindLineEntry(
+                index_ptr, line_number, sc.comp_unit, exact, &line_entry);
+            if (start_idx_ptr != UINT32_MAX)
+              line_number = line_entry.line;
+          }
+          exact = true;
+          start_idx_ptr = index_ptr;
           while (start_idx_ptr <= end_ptr) {
-            LineEntry line_entry;
-            const bool exact = false;
             start_idx_ptr = sc.comp_unit->FindLineEntry(
                 start_idx_ptr, line_number, sc.comp_unit, exact, &line_entry);
             if (start_idx_ptr == UINT32_MAX)


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