[lldb][Editline] Fix crash when navigating through empty command history.
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.
Differential Revision: https://reviews.llvm.org/D100048
GitOrigin-RevId: f49a4440d38a4123b01ded6493a02b4cbf038928
diff --git a/source/Host/common/Editline.cpp b/source/Host/common/Editline.cpp
index fa06bfb..85c62b4 100644
--- a/source/Host/common/Editline.cpp
+++ b/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;
}
diff --git a/test/API/commands/expression/multiline-navigation/TestMultilineNavigation.py b/test/API/commands/expression/multiline-navigation/TestMultilineNavigation.py
index d95e69f..95ad2c8 100644
--- a/test/API/commands/expression/multiline-navigation/TestMultilineNavigation.py
+++ b/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()
