[lldb] Handle empty search string in "memory find"

Given that you'd never find empty string, just error.

Also add a test that an invalid expr generates an error.

Reviewed By: JDevlieghere

Differential Revision: https://reviews.llvm.org/D123793

lldb/source/Commands/CommandObjectMemory.cpp

@@ -1052,9 +1052,14 @@ protected:
 
     DataBufferHeap buffer;
 
-    if (m_memory_options.m_string.OptionWasSet())
+    if (m_memory_options.m_string.OptionWasSet()) {
-      buffer.CopyData(m_memory_options.m_string.GetStringValue());
+      llvm::StringRef str = m_memory_options.m_string.GetStringValue();
-    else if (m_memory_options.m_expr.OptionWasSet()) {
+      if (str.empty()) {
+        result.AppendError("search string must have non-zero length.");
+        return false;
+      }
+      buffer.CopyData(str);
+    } else if (m_memory_options.m_expr.OptionWasSet()) {
       StackFrame *frame = m_exe_ctx.GetFramePtr();
       ValueObjectSP result_sp;
       if ((eExpressionCompleted ==

lldb/test/API/functionalities/memory/find/TestMemoryFind.py

@@ -41,6 +41,11 @@ class MemoryFindTestCase(TestBase):
 
         # Test the memory find commands.
 
+        # Empty search string should be handled.
+        self.expect('memory find -s "" `stringdata` `stringdata+16`',
+                error=True,
+                substrs=["error: search string must have non-zero length."])
+
         self.expect(
             'memory find -s "in const" `stringdata` `stringdata+(int)strlen(stringdata)`',
             substrs=[
@@ -48,6 +53,12 @@ class MemoryFindTestCase(TestBase):
                 '69 6e 20 63',
                 'in const'])
 
+        # Invalid expr is an error.
+        self.expect(
+            'memory find -e "not_a_symbol" `&bytedata[0]` `&bytedata[15]`',
+            error=True,
+            substrs=["error: expression evaluation failed. pass a string instead"])
+
         self.expect(
             'memory find -e "(uint8_t)0x22" `&bytedata[0]` `&bytedata[15]`',
             substrs=[