Data formatters: fix detection of C strings

[jarin]

Summary

Detection of C strings does not work well for pointers. If the value object holding a (char*) pointer does not have an address (e.g., if it is a temp), the value is not considered a C string and its formatting is left to DumpDataExtractor rather than the special handling in ValueObject::DumpPrintableRepresentation. This leads to inconsistent outputs, e.g., in escaping non-ASCII characters. See the test for an example; the second test expectation is not met (without this patch). With this patch, the C string detection only insists that the pointer value is valid. The patch makes the code consistent with how the pointer is obtained in ValueObject::ReadPointedString.

[teemperor]

LGTM, thanks for tracking this down! I only have a minor comment about the test character.

lldb/test/API/functionalities/data-formatter/cstring-utf8-summary/TestCstringUnicode.py

19

expect_expr is the modern way to check this:

self.expect_expr("s", result_summary='"🔥"')
self.expect_expr("(const char*)s", result_summary='"🔥"')

lldb/test/API/functionalities/data-formatter/cstring-utf8-summary/main.cpp

3

Could you make this a string like u8"🔥"? "é" is also a valid character in a lot of extended-ASCII character sets (e.g., Latin-1) and we probably should take some unicode-exclusive character and make sure it's utf-8.

[jarin]

Addressed reviewer comments.

[jarin]

Thanks for the review! Could you possibly land this for me?

lldb/source/Core/ValueObject.cpp

bool ValueObject::IsCStringContainer(bool check_pointer) {
   if (!is_char_arr_ptr)
     return false;
   if (!check_pointer)
     return true;
   if (type_flags.Test(eTypeIsArray))
     return true;
   addr_t cstr_address = LLDB_INVALID_ADDRESS;
   AddressType cstr_address_type = eAddressTypeInvalid;
-  cstr_address = GetAddressOf(true, &cstr_address_type);
+  cstr_address = GetPointerValue(&cstr_address_type);
   return (cstr_address != LLDB_INVALID_ADDRESS);
 }
 
 size_t ValueObject::GetPointeeData(DataExtractor &data, uint32_t item_idx,
                                    uint32_t item_count) {
   CompilerType pointee_or_element_compiler_type;
   const uint32_t type_info = GetTypeInfo(&pointee_or_element_compiler_type);
   const bool is_pointer_type = type_info & eTypeIsPointer;

lldb/test/API/functionalities/data-formatter/cstring-utf8-summary/Makefile

+CXX_SOURCES := main.cpp
+
+include Makefile.rules

lldb/test/API/functionalities/data-formatter/cstring-utf8-summary/TestCstringUnicode.py

+# coding=utf8
+
+import lldb
+from lldbsuite.test.lldbtest import *
+import lldbsuite.test.lldbutil as lldbutil
+
+
+class CstringUnicodeTestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+    NO_DEBUG_INFO_TESTCASE = True
+
+    def test_cstring_unicode(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "// break here",
+            lldb.SBFileSpec("main.cpp", False))
+        self.expect_expr("s", result_summary='"🔥"')
+        self.expect_expr("(const char*)s", result_summary='"🔥"')

lldb/test/API/functionalities/data-formatter/cstring-utf8-summary/main.cpp

+int main() {
+  const char *s = u8"🔥";
+  return 0; // break here
+}