Return actual type from SBType::GetArrayElementType

[werat]

Summary

SBType::GetArrayElementType should return the actual type, not the canonical type (e.g. int32_t, not the underlying int).

Added a test case to validate the new behavior. I also ran all other tests on Linux (ninja check-lldb), they all pass.

[jingham]

This was done on purpose, in commit 902974277d507a149e33487d32e4ba58c41451b6. The comment there is:

Data formatters: Look through array element typedefs

Summary:
Motivation: When formatting an array of typedefed chars, we would like to display the array as a string.

The string formatter currently does not trigger because the formatter lookup does not resolve typedefs for array elements (this behavior is inconsistent with pointers, for those we do look through pointee typedefs). This patch tries to make the array formatter lookup somewhat consistent with the pointer formatter lookup.

So far as I can tell from the discussion in that review, it removed some lower level code that was resolving the typedef too early, then added it at the SB layer to preserve previous behavior, even though that behavior was acknowledged to be not great. There was some promise to come back and fix the SB layer which it doesn't seem like it even happened.

So this patch seems in line with the intent of the previous revision, but Raphael and Greg were the ones active in the review of that older patch, maybe they remember more about this?

[jarin]

The code change looks good to me and it is in line with the change that Raphael and Greg wanted in https://reviews.llvm.org/D72133. As far as I remember, https://reviews.llvm.org/D72133 did not change the previous behavior because I felt that changing API semantics was out of scope of what I wanted to do with the formatters.

Someone else should look at the test. The addition seems to be a bit ad-hoc, but overall reasonable.

[werat]

Btw, I don't have commit access, so would be great if someone could land this for me :) (if everything is OK with this patch).

[werat]

Ping :)
@teemperor @JDevlieghere

[JDevlieghere]

In D90318#2362321, @werat wrote:

Btw, I don't have commit access, so would be great if someone could land this for me :) (if everything is OK with this patch).

I'll land this for you once the test suite finishes.

lldb/source/API/SBType.cpp

return LLDB_RECORD_RESULT(
       SBType(TypeImplSP(new TypeImpl(m_opaque_sp->GetDereferencedType()))));
 }
 
 SBType SBType::GetArrayElementType() {
   LLDB_RECORD_METHOD_NO_ARGS(lldb::SBType, SBType, GetArrayElementType);
 
   if (!IsValid())
     return LLDB_RECORD_RESULT(SBType());
-  CompilerType canonical_type =
-      m_opaque_sp->GetCompilerType(true).GetCanonicalType();
-  return LLDB_RECORD_RESULT(SBType(
-      TypeImplSP(new TypeImpl(canonical_type.GetArrayElementType(nullptr)))));
+  return LLDB_RECORD_RESULT(SBType(TypeImplSP(new TypeImpl(
+      m_opaque_sp->GetCompilerType(true).GetArrayElementType(nullptr)))));
 }
 
 SBType SBType::GetArrayType(uint64_t size) {
   LLDB_RECORD_METHOD(lldb::SBType, SBType, GetArrayType, (uint64_t), size);
 
   if (!IsValid())
     return LLDB_RECORD_RESULT(SBType());
   return LLDB_RECORD_RESULT(SBType(TypeImplSP(

lldb/test/API/python_api/type/TestTypeList.py

def test(self):
         self.DebugSBValue(id)
         id_type = id.GetType()
         self.DebugSBType(id_type)
 
         # SBType.GetBasicType() takes an enum 'BasicType'
         # (lldb-enumerations.h).
         int_type = id_type.GetBasicType(lldb.eBasicTypeInt)
         self.assertTrue(id_type == int_type)
+
+        # Find 'myint_arr' and check the array element type.
+        myint_arr = frame0.FindVariable('myint_arr')
+        self.assertTrue(myint_arr, VALID_VARIABLE)
+        self.DebugSBValue(myint_arr)
+        myint_arr_type = myint_arr.GetType()
+        self.DebugSBType(myint_arr_type)
+        self.assertTrue(myint_arr_type.IsArrayType())
+        myint_arr_element_type = myint_arr_type.GetArrayElementType()
+        self.DebugSBType(myint_arr_element_type)
+        myint_type = target.FindFirstType('myint')
+        self.DebugSBType(myint_type)
+        self.assertTrue(myint_arr_element_type == myint_type)

lldb/test/API/python_api/type/main.cpp

while (t != NULL) {
             ++total;
         t = t->next;
     }
     printf("We have a total number of %d tasks\n", total);
 
     // This corresponds to an empty task list.
     Task *empty_task_head = new Task(-1, NULL);
 
+    typedef int myint;
+    myint myint_arr[] = {1, 2, 3};
+
     return 0; // Break at this line
 }