编译时加上 fno-strict-aliasing 选项,C 和 C++ 均适用,禁用 strict aliasing rule,缺点是在获得便利的同时,也放弃了编译器可能进行的额外的优化(TBAA)。 memcpy of C/C++ 在C 和 C++下,均可以使用 memcpy(), 进行符合 strict aliasing rules 的类型双关。 double foo(double x) { return x; } // 假设...
标签: strict-aliasing 使用static_cast 将任何指针转换为 char 指针 如果根据严格的别名规则 char 指针可能指向任何类型的指针,那么为什么我不能使用 static_cast 将任何类型的指针转换为 char 指针? char*ptr;int*intPtr; ptr =reinterpret_cast<char*>(intPtr);// okptr =static_cast<char*>(int...
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...
什么是Strict Aliasing? 按照理解strict aliasing一文描述: Strict aliasing 是C或C++编译器的一种假设:不同类型的指针绝对不会指向同一块内存区域。 例子 暂且不管这句话,我们看个例子: hello.c #include <stdio.h>int a;int f(float *b){a = 1;*b = 0;return a;}int main(){printf("%d\n", f(...
由于C/C++里头有指针的存在,所以在Strict Aliasing这个规则出来以前,很多人都会做这样的事: uint32_t foo; uint16_t*bar = &foo; bar[0] =1; bar[1] =2; 这个看起来很自然,毕竟,人家就是将一块内存分成两块,然后分别对两块进行操作... 但是,这样...
aliasing rule and your compiler warns you for it. According to the Standard, a compiler is allowed to issue warning diagnostic messages whenever and whereever it wants so that could explain it all. kind regards, Jos Joinz #6 Oct 9 '10, 01:45 AM I just add '-fno-strict-aliasing...
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) 首先看下在不同优化等级下gcc的默认优化参数(此处重点关注fstrict-aliasing 在O0(默认...
这段代码的目的是交换一个int类型的前两个字节和后两个字节,正常编译和加了-O2, -fno-strict-aliasing 选项,程序可以正常运行,但是加了-O2而不加-fno-strict-aliasing 时, 结果并不是我们预期想要的。原因是加了-O2选项,默认打开了-strict-aliasing,程序中的short *p = (short *) &i, 破坏了alia...
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 ...