llvm dev - Aug 2010 - [LLVMdev] LLVM-C: Calling functions contained in other libraries

Hello,

I have a question concerning llvm-c.
I have set up a function that needs to invoke an external method, in a other
library. It has the following signature: void* NSFullUserName(void);
The void* can be replaced with a i8*, that far I was able to get, but when my
call is invoked, the engine gives me the following message:

LLVM ERROR: Tried to execute an unknown external function: i8* ()*
NSFullUserName

I have dumped the module (without the clutter):

declare i8* @NSFullUserName()

define i8* @MyFunction() {
entrypoint:
  %myCall = call i8* @NSFullUserName()            ; <i8*> [#uses=1]
  ret i8* %myCall
}

Where am I going wrong here?

To add some code to my previous question:

LLVMTypeRef i8Ptr(void) {
    return LLVMPointerType(LLVMInt8Type(), 0);
}

LLVMValueRef d(LLVMModuleRef module) {
    LLVMValueRef result;
    LLVMBasicBlockRef block;
    LLVMBuilderRef builder = LLVMCreateBuilder();
    
    LLVMValueRef fullUsername = LLVMAddFunction(module,
"NSFullUserName", LLVMFunctionType(LLVMPointerType(LLVMInt8Type(), 0),
NULL, 0, 0));
    LLVMSetLinkage(fullUsername, LLVMExternalLinkage);
    
    result = LLVMAddFunction(module, "MyFunction",
LLVMFunctionType(i8Ptr(), NULL, 0, 0));
    block = LLVMAppendBasicBlock(result, "entrypoint");
    LLVMPositionBuilderAtEnd(builder, block);
    
    LLVMValueRef returnVal = LLVMBuildCall(builder, fullUsername, NULL, 0,
"myCall");
    LLVMBuildRet(builder, returnVal);
    
    LLVMDisposeBuilder(builder);
    return result;
}


int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    
    char * error = NULL;
    LLVMExecutionEngineRef engine;
    LLVMModuleRef module = LLVMModuleCreateWithName("MyModule");
    
    LLVMValueRef toCall = d(module);
    
    LLVMDumpModule(module);
    
    LLVMLinkInInterpreter();
    LLVMCreateInterpreterForModule(&engine, module, &error);
    
    LLVMGenericValueRef result = LLVMRunFunction(engine, toCall, 0, NULL);
    
    LLVMDisposeModule(module);
    [pool drain];
    return 0;
}


Thank you,

Filip
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On Aug 12, 2010, at 10:43 AM, F van der Meeren wrote:
> Where am I going wrong here?
> 
Did you link against the library that contains the function?

-eric

The function is called in my code, just to be sure it is reachable...

On 12 Aug 2010, at 19:55, Eric Christopher wrote:
> 
> On Aug 12, 2010, at 10:43 AM, F van der Meeren wrote:
> 
>> Where am I going wrong here?
>> 
> 
> Did you link against the library that contains the function?
> 
> -eric

This might be a bug (or feature depending on vision of the software).

I have tried this with the global mapping, and it still won't work.
But by replacing the calling code with the JIT:

    LLVMInitializeNativeTarget();
    LLVMLinkInJIT();
    LLVMCreateJITCompilerForModule(&engine, module, 0, &error);
    //LLVMAddGlobalMapping(engine, toCall, (void*)&NSFullUserName);
    
    LLVMGenericValueRef result = LLVMRunFunction(engine, toCall, 0, NULL);
    NSLog(@"Second attempt: %@", LLVMGenericValueToPointer(result));

It suddenly works like a charm, without any global mapping required.

Filip

On 12 Aug 2010, at 19:55, Eric Christopher wrote:
> 
> On Aug 12, 2010, at 10:43 AM, F van der Meeren wrote:
> 
>> Where am I going wrong here?
>> 
> 
> Did you link against the library that contains the function?
> 
> -eric