Cannot assign string to a json value

[pps83]

That's kind of crazy the problem exists in the library, but the most obvious thing doesn't seem to work:

    Json::Value jmessage;
    std::string sdp;
    jmessage["something"] = sdp;

this results in a link error:

error LNK2019: unresolved external symbol "public: class Json::Value & __thiscall Json::Value::operator=(class Json::Value const &)"

I get this error with when using # define JSONCPP_VERSION_STRING "1.6.5"

If I take current git it doesn't even compile:

2>json/json.h(298): error C2065: 'SecureAllocator': undeclared identifier

In general, those implicit constructors that construct string to Json::Value aren't a good idea IMO. Library should also provide .assign methods. In both case I use amalgamated version

[BillyGoto]

I disagree unless there’s a functional difference between operator= and an assign member function. I guess the parenthetical and operator precedence are different. But operator= is pretty standard! When you said “explicit” did you mean “implicit”? It can be argued whether they are good or bad, I guess. I like them. I think we should be more complete though. If we have an implicit constructor from T, we should provide operators like assignment directly from T as well, so we aren’t doing more work than we need to, converting to Value and then assigning from the temporary Value. This gets expensive for relationals where you are making a Value just to throw it out.

On Sat, Jan 19, 2019 at 3:27 AM PavelP ***@***.***> wrote: That's kind of crazy the problem exists in the library, but the most obvious thing doesn't seem to work: Json::Value jmessage; std::string sdp; jmessage["something"] = sdp; this results in a link error: error LNK2019: unresolved external symbol "public: class Json::Value & __thiscall Json::Value::operator=(class Json::Value const &)" I get this error with when using # define JSONCPP_VERSION_STRING "1.6.5" If I take current git it doesn't even compile: 2>json/json.h(298): error C2065: 'SecureAllocator': undeclared identifier In general, those explicit constructors that construct string to Json::Value aren't a good idea IMO. Library should also provide .assign methods. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#871>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AHFzPKRWci3vWG1NYBQlhKXqMwoU6y3Bks5vEtb9gaJpZM4aJB6u> .

-- ǝnɥɐuop ʎllıq

[pps83]

I disagree unless there’s a functional difference between operator= and an assign member function. I guess the parenthetical and operator precedence are different. But operator= is pretty standard!

No difference, but jsoncpp could like most containers provide .assign that does the same as operator=. That way intellisense can list available methods and you can see right away what you can use to assign a value. When it didn't work, I had to go over entire Value class to see what's available and what happens there and implicit Value ctor just confused me originally, as I was looking for an operator=.

When you said “explicit” did you mean “implicit”? It can be argued whether they are good or bad, I guess. I like them.

Yes, I meant implicit (corrected). I like them too, until they cause unexpected issues.

If we have an implicit constructor from T, we should provide operators like assignment directly from T as well, so we aren’t doing more work than we need to, converting to Value and then assigning from the temporary Value. This gets expensive for relationals where you are making a Value just to throw it out.

Supposedly passing by value and swapping it out should be ok (off course assigning directly would be better), but I have no idea why VS2015 gives a link error in this piece of code. If I change that std::string sdp; to Value sdp; then it links. By the way, that code that I'm trying to build uses ancient jsoncpp version from 2012 and had no issues, but when I updated jsoncpp then I started to get all kinds of compilation/link errors. Just in case, that code is part of chrome browser and webrtc project from google, they use jsoncpp from 2012 and didn't update.

[pps83]

If I take current git it doesn't even compile:

2>json/json.h(298): error C2065: 'SecureAllocator': undeclared identifier

In general, those implicit constructors that construct string to Json::Value aren't a good idea IMO. Library should also provide .assign methods. In both case I use amalgamated version

I just tried minimal example:

#include "json/json.h"

int main()
{
    Json::Value jmessage;
    std::string sdp;
    jmessage["something"] = sdp;
}

and it works with non-amalgamated version and fails to compile with amalgamated one. So, something isn't right with the amalgamation as it results in different results.
Interesting part that I don't get linking error with the minimal example, but I do get link error when building it as part of chrome/webrtc. I didn't try to investigate, perhaps r-value references are disabled or some other compilation flags trigger it, no idea.

[baylesj]

Closing due to inactivity, and looks like it may have been fixed in other patches.