What does __ Stdcall mean?
__stdcall is the calling convention used for the function. __stdcall is the standard calling convention for Win32 system calls. Wikipedia covers the details. It primarily matters when you are calling a function outside of your code (e.g. an OS API) or the OS is calling you (as is the case here with WinMain).
What is Stdcall calling convention?
The stdcall calling convention is a variation on the Pascal calling convention in which the callee is responsible for cleaning up the stack, but the parameters are pushed onto the stack in right-to-left order, as in the _cdecl calling convention. Registers EAX, ECX, and EDX are designated for use within the function.
How do I find the calling convention of a DLL?
2 Answers. If the symbol begins with a _ but has no @ , then it’s __cdecl . If it begins with _ and has a @ it’s __stdcall . If it begins with @ and has another @ , it’s __fastcall .
What is the use of __ cdecl?
You can use the __cdecl keyword to set linkage conventions for function calls in C++ applications. The __cdecl keyword instructs the compiler to read and write a parameter list by using C linkage conventions.
What is calling convention in assembly?
Calling conventions are a standardized method for functions to be implemented and called by the machine. A calling convention specifies the method that a compiler sets up to access a subroutine. In short, the calling convention specifies how a function call in C or C++ is converted into assembly language.
How do you specify a calling convention?
Calling conventions specify how arguments are passed to a function, how return values are passed back out of a function, how the function is called, and how the function manages the stack and its stack frame. In short, the calling convention specifies how a function call in C or C++ is converted into assembly language.
What calling convention does GCC use?
The cdecl (pronounced see-dec-el, short for “C declaration”) calling convention is extremely common as it’s the default x86 (32-bit) calling convention on today’s most popular compilers including GCC, MSVC, and LLVM. It has the following properties: The caller places all arguments to the callee on the stack.
Why do we need calling conventions?
The differences in calling conventions is very important to understand because mismatches can be disastrous. If you have a callee that is cleaning up the stack, and a caller that is also cleaning up the stack, then you’ve stomped the stack by cleaning it up twice!
What’s the purpose of the calling convention?
A calling convention governs how functions on a particular architecture and operating system interact. This includes rules about includes how function arguments are placed, where return values go, what registers functions may use, how they may allocate local variables, and so forth.
Is Fastcall faster?
Since it typically saves at least four memory accesses, yes it is generally faster.
What is x64 shadow space?
The shadow space is the mandatory 32 bytes (4×8 bytes) you must reserve for the called procedure. In short, you can see it as if functions in x64 have a minimum of 4 arguments, but with the value of the 4 first in registers. Things like stack alignment should also be considered when calling x64.