'runtime_error' from c++ not captured in iOS - c++

Question

In my iOS project, I use a C++ module. The C++ module throws exception for some cases and the Objective C++ wrapper fails to catch it. For instance
Here is my HelloWorld.h
#include <string>
using namespace std;
class HelloWorld{
public:
string helloWorld();
};
#endif
Implementation HelloWorld.cpp
#include "HelloWorld.h"
string HelloWorld::helloWorld(){
throw (std::runtime_error("runtime_error")); // Throwing exception to test
string s("Hello from CPP");
return s;
}
Objective C++ wrapper HelloWorldIOSWrapper.h
#import <Foundation/Foundation.h>
#interface HelloWorldIOSWrapper:NSObject
- (NSString*)getHello;
#end
#endif /* HelloWorldIOSWrapper_h */
Implementation HelloWorldIOSWrapper.mm
#import "HelloWorldIOSWrapper.h"
#include "HelloWorld.h"
#implementation HelloWorldIOSWrapper
- (NSString*)getHello{
try {
HelloWorld h;
NSString *text=[NSString stringWithUTF8String: h.helloWorld().c_str()];
return text;
} catch (const std::exception & e) {
NSLog(#"Error %s", e.what());
}
return nil;
}
#end
#import "HelloWorldIOSWrapper.h" is added to the Bridging-Header
And now, when I try to invoke getHello() from controller, app crashes leaving the below message in log
libc++abi: terminating with uncaught exception of type std::runtime_error: runtime_error
dyld4 config: DYLD_LIBRARY_PATH=/usr/lib/system/introspection DYLD_INSERT_LIBRARIES=/Developer/usr/lib/libBacktraceRecording.dylib:/Developer/usr/lib/libMainThreadChecker.dylib:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib
terminating with uncaught exception of type std::runtime_error: runtime_error
I expect that the exception must be caught in the wrapper, but, no idea why is it not caught leading to app crash. What do I miss?

Answer 1

C++ Interoperability
In 64-bit processes, Objective-C exceptions (NSException) and C++
exception are interoperable. Specifically, C++ destructors and
Objective-C #finally blocks are honored when the exception mechanism
unwinds an exception. In addition, default catch clauses—that is,
catch(...) and #catch(...)—can catch and rethrow any exception
On the other hand, an Objective-C catch clause taking a dynamically
typed exception object (#catch(id exception)) can catch any
Objective-C exception, but cannot catch any C++ exceptions. So, for
interoperability, use #catch(...) to catch every exception and #throw;
to rethrow caught exceptions. In 32-bit, #catch(...) has the same
effect as #catch(id exception).
#try {
}
#catch (...) {
}