MSDN帮助文档中关于内联函数学习笔记

淩亂°似流年 2021-11-22 08:16 258阅读 0赞

![SouthEast][]\--------------------------Naked Function Calls关键字在MSDN中--------------------------------------------  
Microsoft Specific  
Functions declared with the naked attribute are emitted without prolog or epilog code, enabling you to write your own custom prolog/epilog sequences using the inline assembler. Naked functions are provided as an advanced feature. They enable you to declare a function that is being called from a context other than C/C++, and thus make different assumptions about where parameters are, or which registers are preserved. Examples include routines such as interrupt handlers. This feature is particularly useful for writers of virtual device drivers (VxDs).  
  
  
实例函数原型：  
\_\_declspec( naked ) int func( int a, int b )  
\{  
\_\_asm ret  
\}  
  
  
\--------------------------Considerations for Writing Prolog/Epilog Code--------------------------  
Microsoft Specific  
Before writing your own prolog and epilog code sequences, it is important to understand how the stack frame is laid out. It is also useful to know how to use the \_\_LOCAL\_SIZE symbol.  
  
  
Stack Frame Layout  
push ebp ; Save ebp  
mov ebp, esp ; Set stack frame pointer  
sub esp, localbytes ; Allocate space for locals  
push <registers> ; Save registers  
  
  
The localbytes variable represents the number of bytes needed on the stack for local variables, and the <registers> variable is a placeholder that represents the list of registers to be saved on the stack. After pushing the registers, you can place any other appropriate data on the stack. The following is the corresponding epilog code:  
  
  
  
  
pop <registers> ; Restore registers  
mov esp, ebp ; Restore stack pointer  
pop ebp ; Restore ebp  
ret ; Return from function  
  
  
The stack always grows down (from high to low memory addresses). The base pointer (ebp) points to the pushed value of ebp. The locals area begins at ebp-2. To access local variables, calculate an offset from ebp by subtracting the appropriate value from ebp.  
  
  
\_\_LOCAL\_SIZE  
The compiler provides a symbol, \_\_LOCAL\_SIZE, for use in the inline assembler block of function prolog code. This symbol is used to allocate space for local variables on the stack frame in custom prolog code.  
  
  
The compiler determines the value of \_\_LOCAL\_SIZE. Its value is the total number of bytes of all user-defined local variables and compiler-generated temporary variables. \_\_LOCAL\_SIZE can be used only as an immediate operand; it cannot be used in an expression. You must not change or redefine the value of this symbol. For example:  
  
  
mov eax, \_\_LOCAL\_SIZE ;Immediate operand--Okay  
mov eax, \[ebp - \_\_LOCAL\_SIZE\] ;Error  
  
  
The following example of a naked function containing custom prolog and epilog sequences uses the \_\_LOCAL\_SIZE symbol in the prolog sequence:  
  
  
// the\_\_local\_size\_symbol.cpp  
// processor: x86  
\_\_declspec ( naked ) int main() \{  
int i;  
int j;  
  
  
\_\_asm \{ /\* prolog \*/  
push ebp  
mov ebp, esp  
sub esp, \_\_LOCAL\_SIZE  
\}  
  
/\* Function body \*/  
\_\_asm \{ /\* epilog \*/  
mov esp, ebp  
pop ebp  
ret  
\}  
\}  
  
  
\------------------------\_\_declspec keyword关键字在MSDN中----------------------------------------------  
The extended attribute syntax for specifying storage-class information uses the \_\_declspec keyword, which specifies that an instance of a given type is to be stored with a Microsoft-specific storage-class attribute listed below. Examples of other storage-class modifiers include the static and extern keywords. However, these keywords are part of the ANSI specification of the C and C++ languages, and as such are not covered by extended attribute syntax. The extended attribute syntax simplifies and standardizes Microsoft-specific extensions to the C and C++ languages.  
  
  
decl-specifier:  
\_\_declspec ( extended-decl-modifier-seq )  
  
  
extended-decl-modifier-seq:  
extended-decl-modifieropt  
  
  
extended-decl-modifier extended-decl-modifier-seq  
  
  
extended-decl-modifier:  
align(\#)  
  
  
allocate("segname")  
  
  
appdomain  
  
  
deprecated  
  
  
dllimport  
  
  
dllexport  
  
  
jitintrinsic  
  
  
naked  
  
  
noalias  
  
  
noinline  
  
  
noreturn  
  
  
nothrow  
  
  
novtable  
  
  
process  
  
  
property(\{get=get\_func\_name|,put=put\_func\_name\})  
  
  
restrict  
  
  
selectany  
  
  
thread  
  
  
uuid("ComObjectGUID")  
  
  
White space separates the declaration modifier sequence. Examples appear in later sections.  
  
  
Extended attribute grammar supports these Microsoft-specific storage-class attributes: align, allocate, appdomain, deprecated, dllexport, dllimport, jitintrinsic, naked, noalias, noinline, noreturn, nothrow, novtable, process, restrict, selectany, and thread. It also supports these COM-object attributes: property and uuid.  
  
  
The dllexport, dllimport, naked, noalias, nothrow, property, restrict, selectany, thread, and uuid storage-class attributes are properties only of the declaration of the object or function to which they are applied. The thread attribute affects data and objects only. The naked attribute affects functions only. The dllimport and dllexport attributes affect functions, data, and objects. The property, selectany, and uuid attributes affect COM objects.  
  
  
The \_\_declspec keywords should be placed at the beginning of a simple declaration. The compiler ignores, without warning, any \_\_declspec keywords placed after \* or & and in front of the variable identifier in a declaration.  
  
  
A \_\_declspec attribute specified in the beginning of a user-defined type declaration applies to the variable of that type. For example:  
  
  
Copy Code  
\_\_declspec(dllimport) class X \{\} varX;  
  
  
  
In this case, the attribute applies to varX. A \_\_declspec attribute placed after the class or struct keyword applies to the user-defined type. For example:  
  
  
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class \_\_declspec(dllimport) X \{\};  
  
  
  
In this case, the attribute applies to X.  
  
  
The general guideline for using the \_\_declspec attribute for simple declarations is as follows:  
  
  
Copy Code  
decl-specifier-seqdeclarator-list;  
  
  
  
The decl-specifier-seq should contain, among other things, a base type (e.g. int, float, a typedef, or a class name), a storage class (e.g. static, extern), or the \_\_declspec extension. The init-declarator-list should contain, among other things, the pointer part of declarations. For example:  
  
  
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\_\_declspec(selectany) int \* pi1 = 0; //OK, selectany & int both part of decl-specifier  
int \_\_declspec(selectany) \* pi2 = 0; //OK, selectany & int both part of decl-specifier  
int \* \_\_declspec(selectany) pi3 = 0; //ERROR, selectany is not part of a declarator  
  
  
  
The following code declares an integer thread local variable and initializes it with a value:  
  
  
Copy Code  
// Example of the \_\_declspec keyword  
\_\_declspec( thread ) int tls\_i = 1;

\----------------------Calling C Functions in Inline Assembly内联汇编中调用C库函数---------Inline Assembler关键字---------

\#include <stdio.h>  
\#include <Windows.h>  
  
  
char format\[\] = "%s %s\\n";  
char hello\[\] = "Hello";  
char world\[\] = "world";  
  
  
//在内嵌汇编中调用C库函数  
int \_\_declspec(naked) main( void )  
\{  
\_\_asm  
\{  
push offset world  
push offset hello  
push offset format  
call dword ptr printf  
add esp,0ch  
  
  
call dword ptr getchar  
  
  
xor eax,eax  
push eax  
push offset world  
push offset hello  
push eax  
call dword ptr MessageBox  
  
  
ret  
\}

说明：内联汇编的使用会影响编译器对代码的优化

[SouthEast]: /images/20211122/86cba85b198740528efffb719a66efd0.png