PInvoke finds some functions but not others

Question

I have a bunch of methods like this:

int add5(int val)
{
    return add5Wrap(val);
}

int instanceMethod(void)
{
    return instanceMethodWrap();
}

int classMethod(void)
{
    return classMethodWrap();
}

void getPropertyString(char * outStr)
{
    outStr = getProperty();
}

void setPropertyString(char * string)
{
    setProperty(string);
}

int start(void)
{
    initialise();
    return 0;
}

And they're declared in a header like this:

int add5(int val);
int instanceMethod(void);
int classMethod(void);
void getPropertyString(char * string);
void setPropertyString(char * string);
int start(void);

And they're compiled together with some objective-C that they interact with into a dylib.

The dylib loads. All the methods run without whining* as far as I can tell, except one.

start() does not run. It gives an EntryPointNotFoundException.

What could be causing this and how can I fix it?

*They still give wrong values because nothing is initialised though.

C# side:

    [DllImport("mydll.dylib")]
    public static extern int start ();

    [DllImport("mydll.dylib")]
    public static extern int add5 (int val);

    [DllImport("mydll.dylib")]
    public static extern int instanceMethod();

    [DllImport("mydll.dylib")]
    public static extern int classMethod();

    start();
    add5(5);

etc.

Answer 1

I found out the answer. I had assumed that the folder MonoMac was looking for the dylib was /Library/Frameworks. In reality it was looking in /usr/lib. The version of the library in /usr/lib was much older than the one in /Library/Frameworks.