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

[DavidSpickett]

Summary

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

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

[DavidSpickett]

Previously this would crash.

Unless we'd rather treat it as \x0 but that could be confusing. You can always search for literal 0 instead.

[JDevlieghere]

LGTM

lldb/source/Commands/CommandObjectMemory.cpp

if (high_addr <= low_addr) {
           "starting address must be smaller than ending address");
       return false;
     }
 
     lldb::addr_t found_location = LLDB_INVALID_ADDRESS;
 
     DataBufferHeap buffer;
 
-    if (m_memory_options.m_string.OptionWasSet())
-      buffer.CopyData(m_memory_options.m_string.GetStringValue());
-    else if (m_memory_options.m_expr.OptionWasSet()) {
+    if (m_memory_options.m_string.OptionWasSet()) {
+      llvm::StringRef str = m_memory_options.m_string.GetStringValue();
+      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 ==
            process->GetTarget().EvaluateExpression(
                m_memory_options.m_expr.GetStringValue(), frame, result_sp)) &&
           result_sp) {
         uint64_t value = result_sp->GetValueAsUnsigned(0);
         llvm::Optional<uint64_t> size =

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

def test_memory_find(self):
         self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
                     substrs=['stopped', 'stop reason = breakpoint'])
 
         # The breakpoint should have a hit count of 1.
         lldbutil.check_breakpoint(self, bpno = 1, expected_hit_count = 1)
 
         # 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=[
                 'data found at location: 0x',
                 '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=[
                 'data found at location: 0x',
                 '22 33 44 55 66'])
 
         self.expect(
             'memory find -e "(uint8_t)0x22" `&bytedata[0]` `&bytedata[2]`',
             substrs=['data not found within the range.'])
 
         self.expect('memory find -s "nothere" `stringdata` `stringdata+5`',
                     substrs=['data not found within the range.'])
 
         self.expect('memory find -s "nothere" `stringdata` `stringdata+10`',
                     substrs=['data not found within the range.'])