WEBVTT 00:01.090 --> 00:07.540 When you call a function, the compiler will create a stack frame for the new function call and it will 00:07.540 --> 00:10.090 push items onto the stack here. 00:10.090 --> 00:19.480 So the data itself, the data put on the stack depends on your compiler, the whether the code is compiled 00:19.480 --> 00:22.060 for the debug or the release build here. 00:22.060 --> 00:30.490 So however, in general the there will be information about the parameters passed here, the information 00:30.490 --> 00:37.690 pass parameters and to the function, the return address here and the address, the name of the function 00:37.690 --> 00:42.100 call here and the automatic variables are located in this function here. 00:42.100 --> 00:47.440 This means that the when you make a function call at a runtime, there will be a memory overhead and 00:47.440 --> 00:53.770 performance overhead from creating the stack frame before the function runs and the performance overhead 00:53.800 --> 00:57.640 in when you clean this function up. 00:57.640 --> 00:59.590 So after the function completes here. 00:59.590 --> 01:06.230 So if a function is inline, this overhead does not occur because the function call will use the current 01:06.230 --> 01:08.180 stack frame rather than a new one. 01:08.180 --> 01:15.320 So clearly the inline function should be small, both in terms of code and the memory used on the stack 01:15.320 --> 01:24.410 here, so the compiler can ignore the inline specifier and call the function with a separate stack frame. 01:24.410 --> 01:29.450 So we can actually specify the call conventions in this cplusplus here. 01:29.480 --> 01:37.310 So when your code uses your own functions, you do not need to pay any attention to calling conventions 01:37.310 --> 01:42.140 because the compiler will make sure that the appropriate convention is used. 01:42.140 --> 01:49.970 So however, if you are writing library code that can be used by other cplusplus compilers or even by 01:49.970 --> 01:53.780 other languages, the calling convention becomes important. 01:53.780 --> 01:59.480 So since this course is not about interoperable code, we won't go into much depth here. 01:59.480 --> 02:05.930 But instead we will look at two aspects function naming and stack maintenance. 02:06.600 --> 02:09.390 So we can also use the C linkage here. 02:09.660 --> 02:15.840 So when you give a C plus plus function a name, this is the name that you will use to call the function 02:15.840 --> 02:18.060 in your C plus plus code. 02:18.090 --> 02:24.810 However, under the covers, the C plus plus compiler will decorate the name with the extra symbols 02:24.810 --> 02:31.890 for the return type and the parameter so that the overloaded functions all have different names. 02:31.890 --> 02:34.730 So to the C plus plus developers. 02:34.740 --> 02:41.430 This is also known as the name mangling mangling. 02:41.430 --> 02:48.060 So if you need to export a function through the shared library, for example, in Windows Dynamic Link 02:48.090 --> 02:54.150 library, this means that that dll files for the. 02:56.590 --> 03:04.570 Shared library library in windows here that dll files here. 03:04.570 --> 03:07.420 So this means dynamic link library. 03:07.420 --> 03:12.010 So you must use the types and names that the other languages can use. 03:12.010 --> 03:19.690 So to do this you can mark a function with the extension C here, this means that function has C linkage 03:19.690 --> 03:28.480 and the compiler will not use the external code and you should not use it with the function that have 03:28.480 --> 03:37.360 return values and parameters that use the C plus plus custom types extern C here like that. 03:37.360 --> 03:38.500 So. 03:39.790 --> 03:46.660 However, if such function does return a cplusplus type, the compiler will only use a warning. 03:46.690 --> 03:54.850 The reason is that the C is a flexible language and the C programmer will able to work out how to turn 03:54.850 --> 03:57.850 the Cplusplus type into something usable. 03:57.850 --> 04:01.890 But it's poor practice to abuse them like this here.