[Lldb-commits] [lldb] [lldb/docs] Fix/improve the gdb command map for dynamic types (PR #138538)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lldb

Author: Pavel Labath (labath)

<details>
<summary>Changes</summary>

The setting and option value names were wrong. I'm assuming this changed over time, but I haven't tried to figure out when.

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Full diff: https://github.com/llvm/llvm-project/pull/138538.diff


1 Files Affected:

- (modified) lldb/docs/use/map.rst (+12-4) 


``````````diff
diff --git a/lldb/docs/use/map.rst b/lldb/docs/use/map.rst
index ed285b2d1f6e9..c648b212006e0 100644
--- a/lldb/docs/use/map.rst
+++ b/lldb/docs/use/map.rst
@@ -800,16 +800,24 @@ Print the dynamic type of the result of an expression
   (gdb) p someCPPObjectPtrOrReference
   (Only works for C++ objects)
 
+LLDB does this automatically if determining the dynamic type does not require
+running the target (in C++, running the target is never needed). This default is
+controlled by the `target.prefer-dynamic-value` setting. If that is disabled, it
+can be re-enabled on a per-command basis:
+
 .. code-block:: shell
 
-  (lldb) expr -d 1 -- [SomeClass returnAnObject]
-  (lldb) expr -d 1 -- someCPPObjectPtrOrReference
+  (lldb) settings set target.prefer-dynamic-value no-dynamic-values
+  (lldb) frame variable -d no-run-target someCPPObjectPtrOrReference
+  (lldb) expr -d no-run-target -- someCPPObjectPtr
 
-or set dynamic type printing to be the default:
+Note that printing of the dynamic type of references is not possible with the
+`expr` command. The workaround is to take the address of the reference and
+instruct lldb to print the children of the resulting pointer.
 
 .. code-block:: shell
 
-  (lldb) settings set target.prefer-dynamic run-target
+  (lldb) expr -P1 -d no-run-target -- &someCPPObjectReference
 
 Call a function so you can stop at a breakpoint in it
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

``````````

</details>


https://github.com/llvm/llvm-project/pull/138538