因为严格别名(strict aliasing)规则的存在,我们很容易写出符合直觉,但是实际上是 Undefined Behavior 的代码。 违反strict aliasing rule 的例1 int foo( float *f, int *i ) { *i = 1; *f = 0.f; return *i; } int main() { int x = 0; std::cout << x << "\n"; // Expect 0,Output...
What is the Strict Aliasing Rule and Why do we care? Understanding Strict Aliasing (翻訳)C/C++のStrict Aliasingを理解する または - どうして#$@##@^%コンパイラは僕がしたい事をさせてくれないの! Options That Control Optimization 严格别名(Strict Aliasing)规则是什么,编译器为什么不做我想做...
The problem with c1 is that it violates C/C++’s “strict aliasing” rule which basically says that if you cast a pointer to a different kind of pointer and then dereference it, then your program has executed anundefined behavior. The pernicious thing about undefined behavior is that it lead...
在编程世界中，我们常常面临抉择，其中一条路径与编译器优化紧密相关，即是否开启严格类型别名规则（-fno-strict-aliasing）的选项。然而，这并不意味着我们可以在所有情况下都忽略这个规则。相反，理解其背后的意义和影响，将帮助我们做出更明智的决策。严格类型别名规则旨在防止类型不匹配和意外的数据操作，...
intmain(){intarr[8] = {1,1,1,1,1,1,1,1};// Little endian: 10000000 | 10000000 ...int8_t*ptr = (int8_t*)arr;// Do we have a violation of the Strict Aliasing rule in this cast?ptr +=3;// 100[0]0000 ...cout<< (int)*ptr <<endl;// outputs 0return1; } Run...
The compiler could've turned off that strict aliasing rule. In release mode however, if the above was true, a direct change of variable i would've been legitimate but your other code (see your OP) breaks that strict aliasing rule and your compiler warns you for it. According to the ...
【3】:http://stackoverflow.com/questions/98650/what-is-the-strict-aliasing-rule(肯定要有stackoverflow。。。) 最后还有一点,关于restrict这个关键字: voidfoo(int* restrict i1,int* restrict i2); 通过restrict关键字,程序员向编译器保证,r1和r2不会指向相同的内存,这样编译器就可以放胆进行优化了。当然...
http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html http://stackoverflow.com/questions/98650/what-is-the-strict-aliasing-rule gcc-vgccversion4.4.5(Ubuntu/Linaro4.4.4-14ubuntu5) arm-none-arm-none-linux-gnueabi-gcc-vgccversion4.3.2(Sourcery G++ Lite 2008q3-72...
理解strict aliasing一文中这样描述: 当两个指针指向同一块区域或对象时,我们称一个指针 alias 另一个指针。 strict aliasing一文中这样描述: Aliasing 是指多于一个的左值指向同一块区域。 比如: 什么是Strict Aliasing? 按照理解strict aliasing一文描述:
we violate the strict aliasing rule. Then the behavior becomes undefined. The output could be as above, if the compiler had optimized the second access, or something completely different, and so your program ends up in a completely unreliable state. Got any C Language Question?# Ask any C ...