tbv2: fix Thrift isset lookups with padding

Thrift isset was failing with a SEGV if the struct contained padding. This is
because we indexed the `isset_indexes` data structure using our field index
rather than the index of the field in Thrift. This then gave a rubbish index
for any exceeding which happens if we have added padding in the middle of the
struct, and this index was looked up in the bitset which can cause a SEGV.

Track a new index `thriftFieldIdx` which is only incremented if we've looked up
a Thrift index.

Namespaced the generated Thrift structs while I was there. This isn't necessary
anymore but cleans things up.

Test plan:
- Added a test case with lots of padding. These don't run in the CI but it
  passes locally.
- `FILTER='OilIntegration.*' make test` - no failures
- `FILTER='OidIntegration.*' make test` - no new failures

oi/CodeGen.cpp

@@ -505,6 +505,7 @@ void CodeGen::getClassSizeFuncConcrete(std::string_view funcName,
             c.fqName() + ">;\n";
   }
 
+  size_t thriftFieldIdx = 0;
   for (size_t i = 0; i < c.members.size(); i++) {
     const auto& member = c.members[i];
     if (member.name.starts_with(AddPadding::MemberPrefix))
@@ -513,8 +514,8 @@ void CodeGen::getClassSizeFuncConcrete(std::string_view funcName,
     if (thriftIssetMember && thriftIssetMember != &member) {
       // Capture Thrift's isset value for each field, except for __isset
       // itself
-      std::string issetIdxStr =
+      std::string issetIdxStr = "thrift_data::isset_indexes[" +
-          "thrift_data::isset_indexes[" + std::to_string(i) + "]";
+                                std::to_string(thriftFieldIdx++) + "]";
       code += "  if (&thrift_data::isset_indexes != nullptr && " + issetIdxStr +
               " != -1) {\n";
       code += "    SAVE_DATA(t." + thriftIssetMember->name + ".get(" +
@@ -684,6 +685,7 @@ void CodeGen::genClassTraversalFunction(const Class& c, std::string& code) {
 
   size_t emptySize = code.size();
   size_t lastNonPaddingElement = getLastNonPaddingMemberIndex(c.members);
+  size_t thriftFieldIdx = 0;
   for (size_t i = 0; i < lastNonPaddingElement + 1; i++) {
     const auto& member = c.members[i];
     if (member.name.starts_with(AddPadding::MemberPrefix)) {
@@ -696,7 +698,7 @@ void CodeGen::genClassTraversalFunction(const Class& c, std::string& code) {
 
     if (thriftIssetMember != nullptr && thriftIssetMember != &member) {
       code += "\n      .write(getThriftIsset(t, ";
-      code += std::to_string(i);
+      code += std::to_string(thriftFieldIdx++);
       code += "))";
     }
 

test/integration/thrift_isset.toml

@@ -1,4 +1,6 @@
 thrift_definitions = '''
+  namespace cpp2 ns_thrift_isset
+
   include "thrift/annotation/cpp.thrift"
   include "thrift/annotation/thrift.thrift"
 
@@ -8,6 +10,18 @@ thrift_definitions = '''
     3: optional i32 c;
   }
 
+  struct MyThriftStructUnpackedPadded {
+    1: optional i32 a;
+    2: optional i64 b;
+    3: optional i32 c;
+    4: optional i64 d;
+    5: optional i32 e;
+    6: optional i64 f;
+    7: optional i32 g;
+    8: optional i64 h;
+    13: optional i32 i;
+  }
+
   @cpp.PackIsset
   struct MyThriftStructPacked {
     1: optional i32 a;
@@ -56,7 +70,7 @@ thrift_definitions = '''
   }
 '''
 raw_definitions = '''
-namespace cpp2 {
+namespace ns_thrift_isset {
   MyThriftStructBoxed::MyThriftStructBoxed() :
         __fbthrift_field_b(),
         __fbthrift_field_c(),
@@ -64,7 +78,7 @@ namespace cpp2 {
         __fbthrift_field_e() {
   }
   MyThriftStructBoxed::~MyThriftStructBoxed() {}
-  MyThriftStructBoxed::MyThriftStructBoxed(::cpp2::MyThriftStructBoxed&& other) noexcept :
+  MyThriftStructBoxed::MyThriftStructBoxed(MyThriftStructBoxed&& other) noexcept :
       __fbthrift_field_a(std::move(other.__fbthrift_field_a)),
       __fbthrift_field_b(std::move(other.__fbthrift_field_b)),
       __fbthrift_field_c(std::move(other.__fbthrift_field_c)),
@@ -72,14 +86,14 @@ namespace cpp2 {
       __fbthrift_field_e(std::move(other.__fbthrift_field_e)),
       __isset(other.__isset) {
   }
-} // namespace cpp2
+} // namespace ns_thrift_isset
 '''
 
 [cases]
   [cases.unpacked]
-    param_types = ["const cpp2::MyThriftStructUnpacked&"]
+    param_types = ["const MyThriftStructUnpacked&"]
     setup = '''
-      cpp2::MyThriftStructUnpacked ret;
+      MyThriftStructUnpacked ret;
       ret.a_ref() = 1;
       ret.c_ref() = 1;
       return ret;
@@ -106,10 +120,52 @@ namespace cpp2 {
       ]
     }]'''
 
-  [cases.packed]
+  [cases.unpacked_padded]
-    param_types = ["const cpp2::MyThriftStructPacked&"]
+    param_types = ["const MyThriftStructUnpackedPadded&"]
     setup = '''
-      cpp2::MyThriftStructPacked ret;
+      MyThriftStructUnpackedPadded ret;
+      ret.a_ref() = 1;
+      ret.c_ref() = 1;
+      return ret;
+    '''
+    features = ["capture-thrift-isset"]
+    expect_json = '''[{
+      "staticSize":80,
+      "dynamicSize":0,
+      "members":[
+        {"name":"__fbthrift_field_a", "staticSize":4, "isset":true},
+        {"name":"__fbthrift_field_b", "staticSize":8, "isset":false},
+        {"name":"__fbthrift_field_c", "staticSize":4, "isset":true},
+        {"name":"__fbthrift_field_d", "staticSize":8, "isset":false},
+        {"name":"__fbthrift_field_e", "staticSize":4, "isset":false},
+        {"name":"__fbthrift_field_f", "staticSize":8, "isset":false},
+        {"name":"__fbthrift_field_g", "staticSize":4, "isset":false},
+        {"name":"__fbthrift_field_h", "staticSize":8, "isset":false},
+        {"name":"__fbthrift_field_i", "staticSize":4, "isset":false},
+        {"name":"__isset", "staticSize":9}
+      ]}]'''
+    expect_json_v2 = '''[{
+      "staticSize":80,
+      "exclusiveSize":19,
+      "size":80,
+      "members":[
+        {"name":"__fbthrift_field_a", "staticSize":4, "is_set":true},
+        {"name":"__fbthrift_field_b", "staticSize":8, "is_set":false},
+        {"name":"__fbthrift_field_c", "staticSize":4, "is_set":true},
+        {"name":"__fbthrift_field_d", "staticSize":8, "is_set":false},
+        {"name":"__fbthrift_field_e", "staticSize":4, "is_set":false},
+        {"name":"__fbthrift_field_f", "staticSize":8, "is_set":false},
+        {"name":"__fbthrift_field_g", "staticSize":4, "is_set":false},
+        {"name":"__fbthrift_field_h", "staticSize":8, "is_set":false},
+        {"name":"__fbthrift_field_i", "staticSize":4, "is_set":false},
+        {"name":"__isset", "staticSize":9, "NOT":"is_set"}
+      ]
+    }]'''
+
+  [cases.packed]
+    param_types = ["const MyThriftStructPacked&"]
+    setup = '''
+      MyThriftStructPacked ret;
       ret.a_ref() = 1;
       ret.c_ref() = 1;
       ret.d_ref() = 1;
@@ -154,9 +210,9 @@ namespace cpp2 {
       ]}]'''
 
   [cases.packed_non_atomic]
-    param_types = ["const cpp2::MyThriftStructPackedNonAtomic&"]
+    param_types = ["const MyThriftStructPackedNonAtomic&"]
     setup = '''
-      cpp2::MyThriftStructPackedNonAtomic ret;
+      MyThriftStructPackedNonAtomic ret;
       ret.a_ref() = 1;
       ret.c_ref() = 1;
       return ret;
@@ -185,9 +241,9 @@ namespace cpp2 {
       ]}]'''
 
   [cases.out_of_order]
-    param_types = ["const cpp2::MyThriftStructOutOfOrder&"]
+    param_types = ["const MyThriftStructOutOfOrder&"]
     setup = '''
-      cpp2::MyThriftStructOutOfOrder ret;
+      MyThriftStructOutOfOrder ret;
       ret.b_ref() = 1;
       return ret;
     '''
@@ -213,9 +269,9 @@ namespace cpp2 {
       ]}]'''
 
   [cases.required]
-    param_types = ["const cpp2::MyThriftStructRequired&"]
+    param_types = ["const MyThriftStructRequired&"]
     setup = '''
-      cpp2::MyThriftStructRequired ret;
+      MyThriftStructRequired ret;
       ret.b_ref() = 1;
       ret.f_ref() = 1;
       return ret;
@@ -248,9 +304,9 @@ namespace cpp2 {
       ]}]'''
 
   [cases.box]
-    param_types = ["const cpp2::MyThriftStructBoxed&"]
+    param_types = ["const MyThriftStructBoxed&"]
     setup = '''
-      cpp2::MyThriftStructBoxed ret;
+      MyThriftStructBoxed ret;
       ret.d_ref() = 1;
       ret.e_ref() = 1;
       return ret;
@@ -281,9 +337,9 @@ namespace cpp2 {
       ]}]'''
 
   [cases.no_capture]
-    param_types = ["const cpp2::MyThriftStructBoxed&"]
+    param_types = ["const MyThriftStructBoxed&"]
     setup = '''
-      cpp2::MyThriftStructBoxed ret;
+      MyThriftStructBoxed ret;
       ret.d_ref() = 1;
       ret.e_ref() = 1;
       return ret;