dbukki
commented
8 months ago Current state
Depending on the kind of CppEntity being parsed, declarations and instantiations/calls may or may not persist additional (duplicate) entities for the relevant pieces of code into the database.
Here are my observations on the current state of our master branch (without any modifications):
Variables
This code produces 3 CppVariable entities, even though they are all technically just declarations:
extern int v0;
extern int v0;
extern int v0;This code also produces 3 CppVariable entities, even though only one of them is the definition:
extern int v1;
int v1;
extern int v1;Note that an AST node is also generated for each of them, so navigation on the UI is working fine.
Records
This code produces no CppRecord entities, as there is no definition:
struct s0;
struct s0;
struct s0;This code produces 1 CppRecord entity for the one definition:
struct s1;
struct s1 {};
struct s1;Note that an AST node is still generated for each of them regardless of definition, so navigation on the UI is working fine.
Functions
This code produces 3 CppFunction entities, even though they are all declarations:
void f0();
void f0();
void f0();This code also produces 3 CppFunction entities, even though only one of them is the definition:
void f1();
void f1() {}
void f1();Note that an AST node is also generated for each declaration and definition as well, so navigation on the UI is working fine.
This code produces 4 CppFunction entities for f2, and 4 CppVariable entities for p0, p1, p2 and the unnamed parameter.
void f2(int p0);
void f2(int p1) {}
void f2(int p2);
void f2(int);Interesting side note: When I select either of the f2 variants on the UI, the Info Tree displays p0 as the parameter of f2, regardless of which declaration I select. It seems that parameter info are queried on a "first entity that matches the function hash" basis. This means that getting rid of multiple CppFunction entities would probably still result in a correct match. If we only generated CppVariable entities for the definition, that would also always result in that name being returned which will actually be used in the function's body. This would be more logical here, as the parameter whose value would actually be used is p1 in this case.
This code produces 5 CppFunction entities for f3, and 5 CppVariable entities for p.
void f3(int p); // in a shared main.h
void f3(int p) {} // in main.cpp, including main.h
void f3(int p = 0); // in def1.cpp, including main.h
void f3(int p = 1); // in def2.cpp, including main.h
void f3(int p = 2); // in def3.cpp, including main.hAgain, an interesting side note here is that regardless of which declaration I select, the default values are not displayed on the Info Tree anyway, so it probably wouldn't matter if the multiple definitions of p were reduced to just one. (Unless the lack of default argument display is already an issue on its own...)
Templates
A similar pattern can be observed with records and functions when making them into templates.
Template records
The following code produces no CppRecord entities, as there is no definition:
template<typename T> struct ts0;
template<typename T> struct ts0;
template<typename T> struct ts0;The following code produces 1 CppRecord entity for the one definition:
template<typename T> struct ts1;
template<typename T> struct ts1 { T value; };
template<typename T> struct ts1;Furthermore, any distinct instantiations of ts1 result in one additional CppRecord entity for the specialized types (3 in this case):
static void use_ts1()
{
ts1<bool > lv0a;// 1 CppRecord for ts1<bool>
ts1<bool > lv0b;// ts1<bool> already accounted for; no record
ts1<long > lv1a;// 1 CppRecord for ts1<long>
ts1<long > lv1b;// ts1<long> already accounted for; no record
ts1<float> lv2a;// 1 CppRecord for ts1<float>
ts1<float> lv2b;// ts1<float> already accounted for; no record
}Similarly, having different names for template parameters has no effect. The code below still produces 1 CppRecord entity:
template<typename T0> struct ts2;
template<typename T1> struct ts2;
template<typename T2> struct ts2;
template<typename T > struct ts2 { T value; };And instantiating it produces another 3 CppRecord entities:
static void use_ts2()
{
ts2<bool > lv0a;// 1 CppRecord for ts2<bool>
ts2<bool > lv0b;// ts2<bool> already accounted for; no record
ts2<long > lv1a;// 1 CppRecord for ts2<long>
ts2<long > lv1b;// ts2<long> already accounted for; no record
ts2<float> lv2a;// 1 CppRecord for ts2<float>
ts2<float> lv2b;// ts2<float> already accounted for; no record
}An interesting side node is that the Info Tree displays ts2 correctly regardless of which declaration I select. Also, when I inspect the type of its value member, it says T. This means that the query (correctly) returns the name corresponding to the definition, and not the alternatives in the declarations (e.g. T0, T1, or T2). This is in contrast with the behavior observed in non-template functions where the first occurrence of the parameter name is returned.
A similar logic applies to having different defaults for the template parameters.
The following code produces 5 CppRecord entities: 1 for the definition in main.h and 4 for the instantiations in the cpp-s:
// in a shared main.h header:
template<typename T> struct ts3 { T value; }; // 1 CppRecord for ts3
// in main.cpp, including main.h:
template<typename T> struct ts3; // no CppRecord; declaration only
static void use_ts3()
{
ts3<int> ta;// 1 CppRecord for ts3<int>
ts3<int> tb;// ts3<int> already accounted for; no record
}
// in def1.cpp, including main.h:
template<typename T = bool> struct ts3;// no CppRecord; declaration only
static void use_ts3()
{
ts3<> ta;// 1 CppRecord for ts3<bool>
ts3<> tb;// ts3<bool> already accounted for; no record
}
// in def2.cpp, including main.h:
template<typename T = long> struct ts3;// no CppRecord; declaration only
static void use_ts3()
{
ts3<> ta;// 1 CppRecord for ts3<long>
ts3<> tb;// ts3<long> already accounted for; no record
}
// in def3.cpp, including main.h:
template<typename T = float> struct ts3;// no CppRecord; declaration only
static void use_ts3()
{
ts3<> ta;// 1 CppRecord for ts3<float>
ts3<> tb;// ts3<float> already accounted for; no record
}Template functions
The following code produces 3 CppFunction entities, even though they are all just declarations:
template<typename T> void tf0();
template<typename T> void tf0();
template<typename T> void tf0();The following code also produces 3 CppFunction entities, even though only one of them is the definition:
template<typename T> void tf1();
template<typename T> void tf1() { T value; }
template<typename T> void tf1();Furthermore, just like with records, any distinct instantiation of tf1 adds an extra CppFunction (3 in this case):
static void use_tf1()
{
tf1<bool >();// 1 CppFunction for tf1<bool>
tf1<bool >();// tf1<bool> already accounted for; no function
tf1<long >();// 1 CppFunction for tf1<long>
tf1<long >();// tf1<long> already accounted for; no function
tf1<float>();// 1 CppFunction for tf1<float>
tf1<float>();// tf1<float> already accounted for; no function
}As expected, changing the name of the template parameter does not change the behavior, the code below still produces 4 CppFunction entities:
template<typename T0> void tf2();
template<typename T1> void tf2();
template<typename T2> void tf2();
template<typename T > void tf2() { T value; }And any distinct instantiations add further CppFunction entities (3 in this case):
static void use_tf2()
{
tf2<bool >();// 1 CppFunction for tf2<bool>
tf2<bool >();// tf2<bool> already accounted for; no function
tf2<long >();// 1 CppFunction for tf2<long>
tf2<long >();// tf2<long> already accounted for; no function
tf2<float>();// 1 CppFunction for tf2<float>
tf2<float>();// tf2<float> already accounted for; no function
}An interesting side note is that whichever declaration of tf2 I select, the Info Tree displays most of the function correctly. However, there is a difference between selecting the definition and any of the declarations:
- Declarations are only displayed in the Declarations section when a declaration is selected.
- No declarations are displayed in the Declarations section if I select the definition.
- The Usage section displays all declarations (including the definition) when a declaration is selected, but none of the instantiations in
use_tf2. - The same Usage section displays only the definition and some (but not all (!?)) instantiations in
use_tf2when the definition is selected.
Finally, a rather curious thing happens when we have different defaults for the template parameter.
The following code produces 6 CppFunction entities: 2 for the definition in main.h (!?) and 1 for the re-declaration in the cpp-s, but no entities for the instantiations/calls (unlike with tf2):
// in a shared main.h header:
template<typename T> void tf3(T&& t) { T value = t; } // this actually produces 2 CppFunction-s for some reason...
// in main.cpp, including main.h:
template<typename T> void tf3(T&& t);// 1 CppFunction for the declaration
static void use_tf3()
{
tf3<int>(0);// no CppFunction for the instantiation of tf3<int>
tf3<int>(0);// no CppFunction for the instantiation of tf3<int>
}
// in def1.cpp, including main.h:
template<typename T = bool> void tf3(T&& t);// 1 CppFunction for the declaration
static void use_tf3()
{
tf3(0);// no CppFunction for the instantiation of tf3<bool>
tf3(0);// no CppFunction for the instantiation of tf3<bool>
}
// in def2.cpp, including main.h:
template<typename T = long> void tf3(T&& t);// 1 CppFunction for the declaration
static void use_tf3()
{
tf3(0);// no CppFunction for the instantiation of tf3<long>
tf3(0);// no CppFunction for the instantiation of tf3<long>
}
// in def3.cpp, including main.h:
template<typename T = float> void tf3(T&& t);// 1 CppFunction for the declaration
static void use_tf3()
{
tf3(0);// no CppFunction for the instantiation of tf3<float>
tf3(0);// no CppFunction for the instantiation of tf3<float>
}I do not have a full explanation for why this happens. There might be more to this issue that has to do with the fact that certain re-declarations reside in different compilation units...
As @dbukki discovered in https://github.com/Ericsson/CodeCompass/pull/714#issuecomment-1983388202, multiple
CppFunctionentities are persisted for each function: one for each declaration and one for the definition.It should be examined whether these multiple entities are truly required or not. Key aspects to focus on during the examination:
CppFunctionentity for declarations, or maybe is it enough to store one for the definition? What will happen in such a case when a function does not have a definition, but only declaration? Would the Info Tree still be able to show the available information about the function?