From bc895dc9cce68bad11bdadcaf53c62c674b780ea Mon Sep 17 00:00:00 2001
From: Alastair Robertson <ajor@meta.com>
Date: Mon, 24 Jul 2023 05:14:53 -0700
Subject: [PATCH] DrgnParser: Always stub function pointers

This makes CodeGen v2 behave the same as CodeGen v1, and there doesn't
seem much point in following function pointers either.
---
 oi/type_graph/DrgnParser.cpp | 15 ++++++++++++++-
 test/test_add_children.cpp   | 34 +++++++++++++++-------------------
 test/test_drgn_parser.cpp    |  8 ++------
 3 files changed, 31 insertions(+), 26 deletions(-)

diff --git a/oi/type_graph/DrgnParser.cpp b/oi/type_graph/DrgnParser.cpp
index a432db1..0a6bfbd 100644
--- a/oi/type_graph/DrgnParser.cpp
+++ b/oi/type_graph/DrgnParser.cpp
@@ -427,6 +427,17 @@ Typedef& DrgnParser::enumerateTypedef(struct drgn_type* type) {
   return makeType<Typedef>(type, name, t);
 }
 
+static drgn_type* getPtrUnderlyingType(drgn_type* type) {
+  drgn_type* underlyingType = type;
+
+  while (drgn_type_kind(underlyingType) == DRGN_TYPE_POINTER ||
+         drgn_type_kind(underlyingType) == DRGN_TYPE_TYPEDEF) {
+    underlyingType = drgn_type_type(underlyingType).type;
+  }
+
+  return underlyingType;
+}
+
 Type& DrgnParser::enumeratePointer(struct drgn_type* type) {
   if (!chasePointer()) {
     return makeType<Primitive>(type, Primitive::Kind::UIntPtr);
@@ -434,7 +445,9 @@ Type& DrgnParser::enumeratePointer(struct drgn_type* type) {
 
   struct drgn_type* pointeeType = drgn_type_type(type).type;
 
-  // TODO why was old CodeGen following funciton pointers?
+  if (drgn_type_kind(getPtrUnderlyingType(type)) == DRGN_TYPE_FUNCTION) {
+    return makeType<Primitive>(type, Primitive::Kind::UIntPtr);
+  }
 
   Type& t = enumerateType(pointeeType);
   return makeType<Pointer>(type, t);
diff --git a/test/test_add_children.cpp b/test/test_add_children.cpp
index 59d74bd..4ce2e26 100644
--- a/test/test_add_children.cpp
+++ b/test/test_add_children.cpp
@@ -65,9 +65,7 @@ TEST_F(AddChildrenTest, InheritancePolymorphic) {
 [0]  Pointer
 [1]    Class: A (size: 16)
          Member: _vptr$A (offset: 0)
-[2]        Pointer
-[3]          Pointer
-               Primitive: void
+           Primitive: uintptr_t
          Member: int_a (offset: 8)
            Primitive: int32_t
          Function: ~A (virtual)
@@ -75,20 +73,20 @@ TEST_F(AddChildrenTest, InheritancePolymorphic) {
          Function: A
          Function: A
          Child
-[4]        Class: B (size: 40)
+[2]        Class: B (size: 40)
              Parent (offset: 0)
                [1]
              Member: vec_b (offset: 16)
-[5]            Container: std::vector (size: 24)
+[3]            Container: std::vector (size: 24)
                  Param
                    Primitive: int32_t
                  Param
-[6]                Class: allocator<int> (size: 1)
+[4]                Class: allocator<int> (size: 1)
                      Param
                        Primitive: int32_t
                      Parent (offset: 0)
-[7]                    Typedef: __allocator_base<int>
-[8]                      Class: new_allocator<int> (size: 1)
+[5]                    Typedef: __allocator_base<int>
+[6]                      Class: new_allocator<int> (size: 1)
                            Param
                              Primitive: int32_t
                            Function: new_allocator
@@ -107,9 +105,9 @@ TEST_F(AddChildrenTest, InheritancePolymorphic) {
              Function: B
              Function: B
              Child
-[9]            Class: C (size: 48)
+[7]            Class: C (size: 48)
                  Parent (offset: 0)
-                   [4]
+                   [2]
                  Member: int_c (offset: 40)
                    Primitive: int32_t
                  Function: ~C (virtual)
@@ -121,9 +119,7 @@ TEST_F(AddChildrenTest, InheritancePolymorphic) {
 [0]  Pointer
 [1]    Class: A (size: 16)
          Member: _vptr.A (offset: 0)
-[2]        Pointer
-[3]          Pointer
-               Primitive: void
+           Primitive: uintptr_t
          Member: int_a (offset: 8)
            Primitive: int32_t
          Function: operator=
@@ -132,17 +128,17 @@ TEST_F(AddChildrenTest, InheritancePolymorphic) {
          Function: ~A (virtual)
          Function: myfunc (virtual)
          Child
-[4]        Class: B (size: 40)
+[2]        Class: B (size: 40)
              Parent (offset: 0)
                [1]
              Member: vec_b (offset: 16)
-[5]            Container: std::vector (size: 24)
+[3]            Container: std::vector (size: 24)
                  Param
                    Primitive: int32_t
                  Param
-[6]                Class: allocator<int> (size: 1)
+[4]                Class: allocator<int> (size: 1)
                      Parent (offset: 0)
-[7]                    Class: new_allocator<int> (size: 1)
+[5]                    Class: new_allocator<int> (size: 1)
                          Param
                            Primitive: int32_t
                          Function: new_allocator
@@ -162,9 +158,9 @@ TEST_F(AddChildrenTest, InheritancePolymorphic) {
              Function: ~B (virtual)
              Function: myfunc (virtual)
              Child
-[8]            Class: C (size: 48)
+[6]            Class: C (size: 48)
                  Parent (offset: 0)
-                   [4]
+                   [2]
                  Member: int_c (offset: 40)
                    Primitive: int32_t
                  Function: operator=
diff --git a/test/test_drgn_parser.cpp b/test/test_drgn_parser.cpp
index f9c5ae4..ae97c37 100644
--- a/test/test_drgn_parser.cpp
+++ b/test/test_drgn_parser.cpp
@@ -543,9 +543,7 @@ TEST_F(DrgnParserTest, VirtualFunctions) {
 [0] Pointer
 [1]   Class: A (size: 16)
         Member: _vptr$A (offset: 0)
-[2]       Pointer
-[3]         Pointer
-              Primitive: void
+          Primitive: uintptr_t
         Member: int_a (offset: 8)
           Primitive: int32_t
         Function: ~A (virtual)
@@ -557,9 +555,7 @@ TEST_F(DrgnParserTest, VirtualFunctions) {
 [0] Pointer
 [1]   Class: A (size: 16)
         Member: _vptr.A (offset: 0)
-[2]       Pointer
-[3]         Pointer
-              Primitive: void
+          Primitive: uintptr_t
         Member: int_a (offset: 8)
           Primitive: int32_t
         Function: operator=