What is __ cdecl in C?

What is __ cdecl in C?

__cdecl is the default calling convention for C and C++ programs. Because the stack is cleaned up by the caller, it can do vararg functions. The __cdecl calling convention creates larger executables than __stdcall, because it requires each function call to include stack cleanup code.

What is Regparm?

regparm ( number ) On x86-32 targets, the regparm attribute causes the compiler to pass arguments number one to number if they are of integral type in registers EAX, EDX, and ECX instead of on the stack. Functions that take a variable number of arguments continue to be passed all of their arguments on the stack.

What calling convention does GCC use?

In Linux, GCC sets the de facto standard for calling conventions. Since GCC version 4.5, the stack must be aligned to a 16-byte boundary when calling a function (previous versions only required a 4-byte alignment). A version of cdecl is described in System V ABI for i386 systems.

What is callee saved?

Callee saved means that the callee has to save the registers and then restore them at the end of the call because they have the guarantee to the caller of containing the same values after the function returns, and it is possible to restore them, even if they are clobbered at some point during the call.

Is __ cdecl standard?

__cdecl is the label of default C/C++ calling convention (named, surprisingly, cdecl ). In simple words, calling convention is the set of rules describing how to call function in assembly (e.g. put arguments to the registers/stack, get the result from EAX/RAX register or from some other place).

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 Vectorcall?

The __vectorcall calling convention on x64 extends the standard x64 calling convention to take advantage of additional registers. Both integer type arguments and vector type arguments are mapped to registers based on position in the argument list. HVA arguments are allocated to unused vector registers.

What is C++ __ Stdcall?

__stdcall means that the arguments to a function are pushed onto the stack from the first to the last. This is as opposed to __cdecl, which means that the arguments are pushed from last to first, and __fastcall, which places the first four (I think) arguments in registers, and the rest go on the stack.

Is RSP caller saved?

On x86-64 Linux, %rbp , %rbx , %r12 , %r13 , %r14 , and %r15 are callee-saved, as (sort of) are %rsp and %rip . The other registers are caller-saved.