[Lldb-commits] [PATCH] D100048: [lldb][Editline] Fix crash when navigating through empty command history.

[Jordan Rupprecht via Phabricator via lldb-commits]

rupprecht created this revision.
rupprecht added a reviewer: JDevlieghere.
rupprecht requested review of this revision.
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An empty history entry can happen by entering the expression evaluator an immediately hitting enter:

  $ lldb
  (lldb) e
  Enter expressions, then terminate with an empty line to evaluate:
    1:  <hit enter>

The next time the user enters the expression evaluator, if they hit the up arrow to load the previous expression, lldb crashes. This patch treats empty history sessions as a single expression of zero length, instead of an empty list of expressions.

Fixes http://llvm.org/PR49845.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D100048

Files:
  lldb/source/Host/common/Editline.cpp
  lldb/test/API/commands/expression/multiline-navigation/TestMultilineNavigation.py


Index: lldb/test/API/commands/expression/multiline-navigation/TestMultilineNavigation.py
===================================================================
--- lldb/test/API/commands/expression/multiline-navigation/TestMultilineNavigation.py
+++ lldb/test/API/commands/expression/multiline-navigation/TestMultilineNavigation.py
@@ -69,3 +69,26 @@
         self.child.expect_exact("(int) $0 = 334")
 
         self.quit()
+
+    @skipIfAsan
+    @skipIfEditlineSupportMissing
+    @expectedFailureAll(oslist=['freebsd'], bugnumber='llvm.org/pr48316')
+    def test_nav_arrow_up_empty_pr49845(self):
+        """Tests that navigating with the up arrow doesn't crash."""
+        self.launch()
+
+        # Create an empty history session by only entering a newline.
+        self.child.sendline("expr")
+        self.child.expect_exact("terminate with an empty line to evaluate")
+        self.child.send("\n")
+        self.expect_prompt()
+
+        # Send just the up arrow in the expression evaluator. This should bring up the previous empty expression.
+        self.child.sendline("expr")
+        self.child.expect_exact("terminate with an empty line to evaluate")
+        self.child.send(self.arrow_up)
+        self.child.expect_exact("1: ")
+        self.child.send("\n")
+        self.expect_prompt()
+
+        self.quit()
Index: lldb/source/Host/common/Editline.cpp
===================================================================
--- lldb/source/Host/common/Editline.cpp
+++ lldb/source/Host/common/Editline.cpp
@@ -153,6 +153,11 @@
     result.push_back(input.substr(start, end - start));
     start = end + 1;
   }
+  // Treat an empty history session as a single command of zero-length instead
+  // of returning an empty vector.
+  if (result.empty()) {
+    result.emplace_back();
+  }
   return result;
 }
 


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