读书笔记，关于pe file的section及pragma命令

The following table shows some of the more common section names and explains each section's purpose.

Section Name	Purpose
.bss	Uninitialized data
.CRT	Read-only C run-time data
.data	Initialized data
.debug	Debugging information
.didata	Delay imported names table
.edata	Exported names table
.idata	Imported names table
.rdata	Read-only run-time data
.reloc	Relocation table information
.rsrc	Resources
.text	.exe's or DLL's code
.tls	Thread-local storage
.xdata	Exception handling table

In addition to the standard sections created by the compiler and the linker, you can create your own sections when you compile using the following directive:

#pragma data_seg("sectionname")

So, for example, I can create a section called "Shared" that contains a single LONG value, as follows:

#pragma data_seg("Shared") LONG g_lInstanceCount = 0; #pragma data_seg()

When the compiler compiles this code, it creates a new section called Shared and places all the initialized data variables that it sees after the pragma in this new section. In the example above, the variable is placed in the Shared section. Following the variable, the #pragma dataseg() line tells the compiler to stop putting initialized variables in the Shared section and to start putting them back in the default data section. It is extremely important to remember that the compiler will store only initialized variables in the new section. For example, if I had removed the initialization from the previous code fragment (as shown in the following code), the compiler would have put this variable in a section other than the Shared section:

#pragma data_seg("Shared") LONG g_lInstanceCount; #pragma data_seg() The Microsoft Visual C++ 6.0 compiler offers an allocate declaration specifier, however, that does allow you to place uninitialized data in any section you desire. Take a look at the following code: *************************************************************************** // Create Shared section & have compiler place initialized data in it. #pragma data_seg("Shared") // Initialized, in Shared section int a = 0;  // Uninitialized, not in Shared section int b;  // Have compiler stop placing initialized data in Shared section. #pragma data_seg() // Initialized, in Shared section _ _declspec(allocate("Shared")) int c = 0;  // Uninitialized, in Shared section  _ _declspec(allocate("Shared")) int d;  // Initialized, not in Shared section int e = 0;  // Uninitialized, not in Shared section int f;   ************************************************************************************************************

--摘自<programming application for Microsoft Windows>

#pragma directives -- 摘自msdn library

Each implementation of C and C++ supports some features unique to its host machine or operating system. Some programs, for instance, need to exercise precise control over the memory areas where data is placed or to control the way certain functions receive parameters. The

#pragma

directives offer a way for each compiler to offer machine- and operating system-specific features while retaining overall compatibility with the C and C++ languages. Pragmas are machine- or operating system-specific by definition, and are usually different for every compiler.

Pragmas can be used in conditional statements, to provide new preprocessor functionality, or to provide implementation-defined information to the compiler. The Microsoft C and C++ compilers recognize the following pragmas:

alloc_text	auto_inline	bss_seg	check_stack
code_seg	comment	component	conform1
const_seg	data_seg	deprecated	function
hdrstop	include_alias	init_seg1	inline_depth
inline_recursion	intrinsic	managed	message
once	optimize	pack	pointers_to_members1
pop_macro	push_macro	runtime_checks	section
setlocale	unmanaged	vtordisp1	warning

1. Supported only by the C++ compiler.

 #pragma                 token-string      

The token-string is a series of characters that gives a specific compiler instruction and arguments, if any. The number sign (

#

) must be the first non-white-space character on the line containing the pragma; white-space characters can separate the number sign and the word

pragma

. Following

#pragma

, write any text that the translator can parse as preprocessing tokens. The argument to

#pragma

is subject to macro expansion.

If the compiler finds a pragma it does not recognize, it issues a warning, but compilation continues.

Some pragmas provide the same functionality as compiler options. When a pragma is encountered in source code, it overrides the behavior specified by the compiler option. For example, if you specified tabindex="0" keywords="_core_.2f.Zp">/Zp8, you can override this compiler setting for specific portions of the code with pack:

cl /Zp8 ...

<file> - packing is 8
// ...
#pragma pack(push, 1) - packing is now 1
// ...
#pragma pack(pop) - packing is 8
</file>