Guide to Advanced Programming in C

Many operating systems provide interface to control access over memory regions to protect memory against unintended read/write operations such as Posix mprotect . These mechanisms usually apply to whole memory pages. (mprotect以page为单位)

http://www.cs.nyu.edu/exact/core/doc/stackOverflow.txt 给出了每个平台默认stack大小以及修改方法

Stack Overflow Problems
=======================
This file gives some hints on addressing this problem on different platforms.

Under Unix-like systems, programs may throw a "Segmentation Fault"
error.  This can be due to stack overflow, especially from recursive
function calls or huge data sets.  In our demo program "Pi"
(see "$(CORE_PATH)/progs/pi"), we compute Pi to any number of desired
bits or digits.  Here are some test results on when stack overflows
will occur on different platforms, using their default stack sizes.

	platform	default size	# bits	# digits
        ===============================================================
	SunOS/Solaris	8172K bytes	<=39875	<=12003	(Shared Version)
	Linux 		8172K bytes	<=62407	<=18786
	Windows		1024K bytes	<=10581	<=3185	(Release Version)
	cygwin		2048K bytes	<=3630	<=1092

If we now change their stack size to their maximum, our Pi program can
compute more bits.

	platform	stack size	# bits		# digits
        ===============================================================
	SunOS/Solaris	unlimited	>=100,000	30102
	Linux		8172K bytes	<=33,219,282	<=10,000,000(?)
	Windows		32768K bytes	<=343077	<=12041

How to change the default stack size on different platforms:
In general, under Unix-like platforms, the stack size is controlled
by environment variable, not the program itself.
So you cannot pass any flags to the
compilers, like gcc, to setup stack size.  Under Windows platforms, the
stack size information is contained in the executable files.  It can be set
during compilation in Visual C++, but this is not available in gcc.
Alternatively, Microsoft provides a program "editbin.exe" which can change the
executable files directly.  Here are more details:

SunOS/Solaris:
==============
	> limit			 # shows the current stack size
	> unlimit		 # changes the stack size to unlimited
	> setenv STACKSIZE 32768 # limits the stack size to 32M bytes

Linux:
======
	> ulimit -a		# shows the current stack size
	> ulimit -s 32768	# sets the stack size to 32M bytes

Windows (during compilation):
=============================
	1. Select "Project->Setting".
	2. Select "Link" page.
	3. Select "Category" to "Output".
	4. Type your preferred stack size in "Reserve:" field under "Stack
	   allocations". eg, 32768 in decimal or 0x20000 in hexadecimal.

Windows (to modify the executable file):
=======================================
There are two programs included in Microsoft Visual Studio, "dumpbin.exe"
 and "editbin.exe".  Run "dumpbin /headers executable_file", and you can see
the "size of stack reserve" information in "optional header values".  Run
"editbin /STACK:size" to change the default stack size.

__attribute__ ((visibility (<value>))) 可以用来控制符号可见域，其中value可以指定为

• "default" # 对其他单元可见
• "hidden" # 仅对本单元可见

然后我们还能够通过编译选项-fvisibility来控制可见域默认值。

inline __attribute__((always _inline)) 可以强制inline.

通常编译器都会提供对应的头文件（提供指令以及数据类型）

• x86: x86intrin.h
• MMX: mmintrin.h
• SSE: xmmintrin.h
• SSE2: emmintrin.h
• SSE3: mm3dnow.h
• 3dnow: tmmintrin.h
• AVX: immintrin.h

SIMD指令操作参数通常要求字节对齐（比如16字节），头文件里面应该都会定义这些数据类型

/* SSE2 */
typedef double __v2df __attribute__ ((__vector_size__ (16)));
typedef long long __v2di __attribute__ ((__vector_size__ (16)));
typedef int __v4si __attribute__ ((__vector_size__ (16)));
typedef short __v8hi __attribute__ ((__vector_size__ (16)));
typedef char __v16qi __attribute__ ((__vector_size__ (16)));