Why Clang++ doesn't run the global object constructor in another static library?

Question

We have an library static_library.a build by clang++, and there is a file bar.cpp include an global object Foo.

But when we use the library in App layer Xcode project, but the global object Foo constructor doesn't been called. (The global object constructor will do some registration job, and impact the app behavior.)

We think the translation unit are not linked into the executable file.

//bar.cpp in static_library.a
class Foo
{
public:
   Foo()
   {
       std::cout << " constructor called" << std::endl;
   }
};

Foo a;
// <------If this function is called in the App layer project, the
// global constructor object will be called. 
Foo* getInstance()  
{
   return &a;
}

So does there any flag, which can control this behavior?

a better way to control would be to have static variable in getInstance function, whenever the function is called your object will be instantiated — Sarang, Apr 23 '15 at 04:08
But there are a lot of global variable in a lot of translation unit, so we cannot list all of them. — ZijingWu, Apr 23 '15 at 06:26
@jtbandes, -all_load works. If you can make it an answer, I will make it as the correct one. Thanks. — ZijingWu, Apr 23 '15 at 06:27

score 1 · Accepted Answer · edited May 23 '17 at 11:43

1

You most likely need the -all_load linker flag.

This question has more details. You may also be interested in -ObjC or -force_load.

edited May 23 '17 at 11:43

Community

1
1

answered Apr 23 '15 at 06:30

jtbandes

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I didn't find much information about `-all_load` in the google. Without the `-all_load`, seams the behaviour voliate the C++ standard. So why clang++ have that and make it default? – ZijingWu Apr 26 '15 at 03:00
1

@ZijingWu: It's the linker's fault, not clang's, it's because that module isn't referenced from other (needed) modules. – Thomas Apr 26 '15 at 10:55

Why Clang++ doesn't run the global object constructor in another static library?

1 Answers1