Compiler issue with Xcode 15.3 & C++20
Closed this issue · 27 comments
asnagni commented
Hi,
I'm trying to use your library in our project using a c++20 compiler (the IDE is Xcode) and we are having a compilation error（Please see attachments).
Could you please let me know how we can fix it effectively without braking your code.
Thank you,
Stay safe
macmade commented
I just tried to compile and test the library with C++20 without issues.
Based on the compiler error, it looks like you're not using it properly.
Can you show the code which calls DictionaryFromMap?
(it would be great if you could avoid posting code screenshots, by the way)
asnagni commented
I can send you the file.
… On Apr 3, 2024, at 1:25 PM, JD Gadina ***@***.***> wrote:
I just tried to compile and test the library with C++20 without issues.
Based on the compiler error, it looks like you're not using it properly.
Can you show the code which calls DictionaryFromMap?
(it would be great if you could avoid posting code screenshots, by the way)
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macmade commented
Just post the code calling into DictionaryFromMap here...
asnagni commented
Please see attachment. It’s a big file, lot of things are going on.

For “MapFromDictionary” Check on line:
1) 5354
2) 5582
3) 9467
4) 9963
5) 10009
We are so using the string a vector converters.
By the way it’s a great library. It was working fine using C++ 11 & 14 but we are having a problem when we moved to C++20
Thank you,
Stay safe
… On Apr 3, 2024, at 1:25 PM, JD Gadina ***@***.***> wrote:
I just tried to compile and test the library with C++20 without issues.
Based on the compiler error, it looks like you're not using it properly.
Can you show the code which calls DictionaryFromMap?
(it would be great if you could avoid posting code screenshots, by the way)
—
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asnagni commented
Ok let me do that.
… On Apr 3, 2024, at 2:04 PM, Alain-Serge Nagni ***@***.***> wrote:
Please see attachment. It’s a big file, lot of things are going on.
<AppController.mm>
For “MapFromDictionary” Check on line:
1) 5354
2) 5582
3) 9467
4) 9963
5) 10009
We are so using the string a vector converters.
By the way it’s a great library. It was working fine using C++ 11 & 14 but we are having a problem when we moved to C++20
Thank you,
Stay safe
> On Apr 3, 2024, at 1:25 PM, JD Gadina ***@***.***> wrote:
>
>
> I just tried to compile and test the library with C++20 without issues.
>
> Based on the compiler error, it looks like you're not using it properly.
> Can you show the code which calls DictionaryFromMap?
>
> (it would be great if you could avoid posting code screenshots, by the way)
>
> —
> Reply to this email directly, view it on GitHub <#3 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AI54DTEKDNOOMNUBLLKAJSLY3Q3Q7AVCNFSM6AAAAABFVTWQK2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDAMZVGE3TMNZSGQ>.
> You are receiving this because you authored the thread.
>
asnagni commented
Example 1:
id mediaObject = [pMediaDictionary objectForKeyedSubscript:mediaMapKey];
std::map <std::string, std::string> mediaItem;
mediaItem = ObjectiveCPP::MapFromDictionary< std::string, NSString >(mediaObject, @selector( cppString ) );
Example 2:
id bonuxObject = [pBonusDictionary objectForKeyedSubscript:bonusMapKey];
std::map <std::string, std::string> bonusItem;
bonusItem = ObjectiveCPP::MapFromDictionary< std::string, NSString >(bonuxObject, @selector( cppString ) );
Example 3:
m_groupsMap = ObjectiveCPP::MapFromDictionary< std::string, NSString >(documentDiff.document.data[@"groups"],
@selector( cppString ) );
Thank you,
Stay safe
… On Apr 3, 2024, at 2:04 PM, JD Gadina ***@***.***> wrote:
Just post the code calling into DictionaryFromMap here...
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macmade commented
I don't think these are the lines causing your issue.
I can compile this code with Xcode 15.3 and C++ 20 without errors.
There's also a unit test for that case:
Objective-CPP/Unit-Tests/Test-Map.mm
Line 181 in 05e2775
Based on the compiler error you showed, you're calling MapFromDictionary with 3 arguments.
Please show the relevant code.
asnagni commented
Hi,
Thank for the link, I do appreciate. I did triple check again and in the code that I sent you there is no call with 3 parameters.
The only place that there is 3 parameters are passed to MapFromDictionary with 3 arguments. It is in Objective-CPP. I did a global search to show you. Please check the screenshot below.

This is the code from Objective-CPP passing 3 parameters:
template < typename T, typename ObjCClass >
std::map< T, T > MapFromDictionary( NSDictionary * dictionary, SEL getter )
{
return MapFromDictionary< T, T, ObjCClass, ObjCClass >( dictionary, getter, getter );
}
Thank you.
… On Apr 3, 2024, at 2:22 PM, JD Gadina ***@***.***> wrote:
I don't think these are the lines causing your issue.
I can compile this code with Xcode 15.3 and C++ 20 without errors.
There's also a unit test for that case:
https://github.com/macmade/Objective-CPP/blob/05e277553cdf0e34669ab8204d177d27d918950d/Unit-Tests/Test-Map.mm#L181
Based on the compiler error you showed, you're calling MapFromDictionary with 3 arguments.
Please show the relevant code.
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macmade commented
Can you show me the complete compiler error from Xcode's build log?
asnagni commented
Sure, please see below:
Candidate function template not viable: no known conversion from 'NSString *(^)(const std::string &)' to 'SEL _Nonnull' for 2nd argument
Candidate function template not viable: requires 2 arguments, but 3 were provided
… On Apr 3, 2024, at 2:49 PM, JD Gadina ***@***.***> wrote:
Can you show me the complete compiler error from Xcode's build log?
Xcode.png (view on web) <https://github.com/macmade/Objective-CPP/assets/146476/e3c453a8-b5e3-412d-b19d-4ebac1a39fa7>
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asnagni commented
I just checked the code in Objective-CPP where we are passing 3 arguments. It's in Map.mm
This is what I see:
#import <ObjectiveCPP.hpp>
namespace ObjectiveCPP
{
NSDictionary * DictionaryFromMap( const std::map< std::string, std::string > & map )
{
return DictionaryFromMap< std::string, std::string, NSString, NSString >
(
map,
^( const std::string & s )
{
return [ [ NSString alloc ] initWithCPPString: s ];
},
^( const std::string & s )
{
return [ [ NSString alloc ] initWithCPPString: s ];
}
);
}
}
… On Apr 3, 2024, at 2:49 PM, JD Gadina ***@***.***> wrote:
Can you show me the complete compiler error from Xcode's build log?
Xcode.png (view on web) <https://github.com/macmade/Objective-CPP/assets/146476/e3c453a8-b5e3-412d-b19d-4ebac1a39fa7>
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asnagni commented
I just took a screenshot. That mau=y help identify the issue:

… On Apr 3, 2024, at 2:49 PM, JD Gadina ***@***.***> wrote:
Can you show me the complete compiler error from Xcode's build log?
Xcode.png (view on web) <https://github.com/macmade/Objective-CPP/assets/146476/e3c453a8-b5e3-412d-b19d-4ebac1a39fa7>
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asnagni commented
In case you can read the compiler message on the screenshot, this is the message:
No matching function for call to ‘DictionaryFromMap'
Thank you.
… On Apr 3, 2024, at 3:13 PM, Alain-Serge Nagni ***@***.***> wrote:
I just took a screenshot. That mau=y help identify the issue:
<Untitled 3.png>
> On Apr 3, 2024, at 2:49 PM, JD Gadina ***@***.***> wrote:
>
>
> Can you show me the complete compiler error from Xcode's build log?
>
> Xcode.png (view on web) <https://github.com/macmade/Objective-CPP/assets/146476/e3c453a8-b5e3-412d-b19d-4ebac1a39fa7>
> —
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> You are receiving this because you authored the thread.
>
macmade commented
I need the complete compiler error.
You can expand the message to get more details:
asnagni commented
That all it is giving me. But Xcode is not very smart for helping. Let me make a build clean and build again. Perhaps it will give me more information.
… On Apr 3, 2024, at 3:19 PM, JD Gadina ***@***.***> wrote:
I need the complete compiler error.
You can expand the message to get more details:
Error.png (view on web) <https://github.com/macmade/Objective-CPP/assets/146476/f4b596a0-4db5-4632-a37b-dfced72de777>
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macmade commented
Go to the build log, click on the failed build action, expand the message, as shown in the screenshot.
It will give the information I need.
asnagni commented
Ok this is entire output:
/////
iphoneos/Objects-normal/arm64/Map.o /Users/asnagni/project/system/AxmolPojects/BeBetter/libs/ObjectiveCPP/source/Map.mm normal arm64 objective-c++ com.apple.compilers.llvm.clang.1_0.compiler (in target 'BeBetter' from project 'BeBetter')
cd /Users/asnagni/project/system/AxmolPojects/BeBetter
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -x objective-c++ -ivfsstatcache /Users/asnagni/Library/Developer/Xcode/DerivedData/SDKStatCaches.noindex/iphoneos17.4-21E210-99a79c02cfa501706f5b564e46d84afe.sdkstatcache -fmessage-length\=0 -fdiagnostics-show-note-include-stack -fmacro-backtrace-limit\=0 -fno-color-diagnostics -Wno-trigraphs -Wno-missing-field-initializers -Wno-missing-prototypes -Wno-return-type -Wno-implicit-atomic-properties -Wno-objc-interface-ivars -Wno-arc-repeated-use-of-weak -Wno-non-virtual-dtor -Wno-overloaded-virtual -Wno-exit-time-destructors -Wno-missing-braces -Wparentheses -Wswitch -Wno-unused-function -Wno-unused-label -Wno-unused-parameter -Wno-unused-variable -Wunused-value -Wno-empty-body -Wno-uninitialized -Wno-unknown-pragmas -Wno-shadow -Wno-four-char-constants -Wno-conversion -Wno-constant-conversion -Wno-int-conversion -Wno-bool-conversion -Wno-enum-conversion -Wno-float-conversion -Wno-non-literal-null-conversion -Wno-objc-literal-conversion -Wshorten-64-to-32 -Wno-newline-eof -Wno-selector -Wno-strict-selector-match -Wno-undeclared-selector -Wno-deprecated-implementations -Wno-c++11-extensions -Wno-implicit-fallthrough -fstrict-aliasing -Wprotocol -Wdeprecated-declarations -Winvalid-offsetof -Wno-sign-conversion -Wno-infinite-recursion -Wno-move -Wno-comma -Wno-block-capture-autoreleasing -Wno-strict-prototypes -Wno-range-loop-analysis -Wno-semicolon-before-method-body -index-store-path /Users/asnagni/Library/Developer/Xcode/DerivedData/BeBetter-cgednnbzvqjspmazshcdqxoodebr/Index.noindex/DataStore @/Users/asnagni/project/system/AxmolPojects/BeBetter/build_ios_arm64/build/BeBetter.build/Debug-iphoneos/Objects-normal/arm64/af3fcb34312c57c0f52879cdce924b91-common-args.resp -MMD -MT dependencies -MF /Users/asnagni/project/system/AxmolPojects/BeBetter/build_ios_arm64/build/BeBetter.build/Debug-iphoneos/Objects-normal/arm64/Map.d --serialize-diagnostics /Users/asnagni/project/system/AxmolPojects/BeBetter/build_ios_arm64/build/BeBetter.build/Debug-iphoneos/Objects-normal/arm64/Map.dia -c /Users/asnagni/project/system/AxmolPojects/BeBetter/libs/ObjectiveCPP/source/Map.mm -o /Users/asnagni/project/system/AxmolPojects/BeBetter/build_ios_arm64/build/BeBetter.build/Debug-iphoneos/Objects-normal/arm64/Map.o
/Users/asnagni/project/system/AxmolPojects/BeBetter/libs/ObjectiveCPP/source/Map.mm:36:16: error: no matching function for call to 'DictionaryFromMap'
return DictionaryFromMap< std::string, std::string, NSString, NSString >
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /Users/asnagni/project/system/AxmolPojects/BeBetter/libs/ObjectiveCPP/source/Map.mm:30:
In file included from /Users/asnagni/project/system/AxmolPojects/BeBetter/libs/ObjectiveCPP/include/ObjectiveCPP.hpp:45:
/Users/asnagni/project/system/AxmolPojects/BeBetter/libs/ObjectiveCPP/include/ObjectiveCPP/Map.hpp:49:20: note: candidate function template not viable: no known conversion from 'NSString *(^)(const std::string &)' to 'SEL _Nonnull' for 2nd argument
NSDictionary * DictionaryFromMap( const std::map< TK, TV > & map, SEL initMethodK, SEL initMethodV )
^
/Users/asnagni/project/system/AxmolPojects/BeBetter/libs/ObjectiveCPP/include/ObjectiveCPP/Map.hpp:93:20: note: candidate function template not viable: requires 2 arguments, but 3 were provided
NSDictionary * DictionaryFromMap( const std::map< T, T > & map, SEL initMethod )
^
1 error generated.
… On Apr 3, 2024, at 3:33 PM, JD Gadina ***@***.***> wrote:
Go to the build log, click on the failed build action, expand the message, as shown in the screenshot.
It will give the information I need.
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macmade commented
I just tested with iOS, no problem with C++20.
Which version of Objective-CPP are you using?
asnagni commented
We downloaded the latest one. On the website.
… On Apr 3, 2024, at 4:11 PM, JD Gadina ***@***.***> wrote:
I just tested with iOS, no problem with C++20.
Which version of Objective-CPP are you using?
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asnagni commented
Hi,
I looked at carefully the Objective-CPP code and I was able to make 2 changes and I’m able to have to compile now:
1) I renamed the function “MapFromDictionary” with 3 parameters from “MapFromDictionary" to “MapFromDictionaryInternal” . I need to make the change a two place. Where it was defined and where it was called.
2) I was having a second issue in the Map.mm file reported by the compiler that I shared with you: Therefore I reverted back the Objective-CPP code to the previous code that you used to have. So I went from a) to b):
a:
namespace ObjectiveCPP
{
NSDictionary * DictionaryFromMap( const std::map< std::string, std::string > & map )
{
return DictionaryFromMap< std::string, std::string, NSString, NSString >
(
map,
^( const std::string & s )
{
return [ [ NSString alloc ] initWithCPPString: s ];
},
^( const std::string & s )
{
return [ [ NSString alloc ] initWithCPPString: s ];
}
);
}
}
b:
namespace ObjectiveCPP
{
NSDictionary * DictionaryFromMap( const std::map< std::string, std::string > & map )
{
return DictionaryFromMap< std::string, std::string, NSString, NSString >( map, @selector( initWithCPPString: ), @selector( initWithCPPString: ) );
}
}
Please let me know if you want me to send you the 2 files that I modified.
… On Apr 3, 2024, at 4:11 PM, JD Gadina ***@***.***> wrote:
I just tested with iOS, no problem with C++20.
Which version of Objective-CPP are you using?
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macmade commented
Please format code when you post…
macmade commented
Your compiler output is odd.
I guess you're not using the provided library but instead compiling the sources directly into your project.
There's no reason for your changes. The whole library builds fine with C++20 as is.
It means your Xcode project is not set-up properly.
asnagni commented
Hi,
Yes you are right, I’m building from the source. I will try by the end of the day to use the provided library and see how it works. I will be using the lastest library you provided. I will keep you posted.
Thank you.
… On Apr 4, 2024, at 4:18 AM, JD Gadina ***@***.***> wrote:
Your compiler output is odd.
I guess you're not using the provided library but instead compiling the sources directly into your project.
There's no reason for your changes. The whole library builds fine with C++20 as is.
It means your Xcode project is not set-up properly.
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asnagni commented
By the way, which version should I use? Just to make sure I’m getting the correct version.
Thank you
… On Apr 4, 2024, at 4:18 AM, JD Gadina ***@***.***> wrote:
Your compiler output is odd.
I guess you're not using the provided library but instead compiling the sources directly into your project.
There's no reason for your changes. The whole library builds fine with C++20 as is.
It means your Xcode project is not set-up properly.
—
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asnagni commented
Thank you.
… On Apr 4, 2024, at 7:58 AM, JD Gadina ***@***.***> wrote:
Latest commit from main, that is 05e2775 <05e2775>
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macmade commented
Closing...
Feel free to reopen if you still have issues.