Hi Havoc, Hi All! :-) >The return value has to be stored in memory somewhere; if the >compiler thinks there is no return value when invoking the >function pointer it doesn't have to make that memory. But if the >function being invoked has a return value it will put the return >value there anyway. I was going to take this to private email with Havoc, but I decided it MIGHT be of interest to the list. The reason being is that some gtk signal CALLBACK can return values and others may not. In fact one of the MOST powerful features of GTK is the almost infinite variety of signatures that one can use with callback functions. Thus we all might run into a situation where we have a mismatch with the return type. Merely calling a function with that returns a value when the compiler thinks it returns void will NOT cause a problem on ANY machine/compiler combination of which I am aware. C/C++ compilers generally just place the return value in a register and leave it at that. On the ix86 series, calling "return 0" merely loads EAX with 0. In the case of structures, things are a little more complicated, but the same principle applies. All that matters is what you DO with the return value. If your function returns void, and the caller THINKS a value is being returned, and attempts to use the return value, it will use whatever random garbage is in the accumulator (EAX) register. If the caller THINKS the function returns void (which is what we were originally discussing) I cannot think of ANY situation where this would cause problems since the caller will simply ignore the [valid] data in EAX. Of course if you are returning the address of some malloced structure [in EAX] and ignore that, you will get a memory leak, but that is ENTIRELY another story! ;-) In summary, substituting a non void function in place of a function that returns void should not cause a problem. I apologise to anyone who thinks this OTO for this list. However, given the almost unlimited flexibility of gtk signals, this may become an issue for some of us. In addition, understanding how return values work is essential for calling and interfacing assembler routines from C/C++. In otherwords to return a value to a C caller from an assembly routine, simply load EAX with the value before returning from the function. (And of course, if you are using C++, do not forget to declare the asm routine as extern "C"! ;-) -- To unsubscribe: mail -s unsubscribe [EMAIL PROTECTED] < /dev/null
