GCC：程序不能与编译选项-O3一起工作 [英] GCC: program doesn't work with compilation option -O3

问题描述

我编写一个C ++程序，当我用优化（选项-O1，-O2，-O3等）编译它不工作（我得到一个分段错误），但它工作很好，当我编译它没有优化。

有错误在我的代码有任何机会吗？或者我应该假设这是GCC中的错误吗？

我的GCC版本是3.4.6。

这种问题有什么已知的解决方法吗？

我的程序的优化和未优化版本之间的速度有很大的区别，所以我真的需要使用优化。

---

这是我原来的函子。一个工作正常，没有任何水平的优化和抛出一个分段错误与任何级别的优化：

  struct distanceToPointSort {
 indexedDocument * point; 
 distanceToPointSort（indexedDocument * p）：point（p）{} 
 bool operator（）（indexedDocument * p1，indexedDocument * p2）{
 return distance（point，p1）距离（点，p2）; 
} 
}; 
  

这个工具完美无缺地与任何级别的优化：

  struct distanceToPointSort {
 indexedDocument * point; 
 distanceToPointSort（indexedDocument * p）：point（p）{} 
 bool operator（）（indexedDocument * p1，indexedDocument * p2）{
 
 float d1 = p1）; 
 float d2 = distance（point，p2）; 
 
 std :: cout<< ; //没有这行，我得到一个分段错误无论如何
 
 return d1< d2; 
} 
};不幸的是，这个问题很难重现，因为它发生在一些特定的值。 
解决方案
 / div> 
现在你发布了代码片段，并找到一个工作的解决方法（@Windows程序员的答案），我可以说，你可能要找的是 -ffloat-store 。
 
 
 -ffloat-store 
 
 
 
并禁止可能改变是否从寄存器或存储器中获取浮点值的其他选项。
 
 
 
此选项可防止机器上出现不必要的过度精度，例如68000其中（68881的）浮动寄存器保持比双精度更精确。类似地对于x86架构。对于大多数程序，超额精度只是好的，但几个程序依赖于IEEE浮点的精确定义。对这些程序使用-float-store，在修改它们以将所有相关的中间计算存储到变量中之后。 
 
 
资料来源： http://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Optimize-Options.html  
 
I'm writing a C++ program that doesn't work (I get a segmentation fault) when I compile it with optimizations (options -O1, -O2, -O3, etc.), but it works just fine when I compile it without optimizations.

Is there any chance that the error is in my code? or should I assume that this is a bug in GCC?

My GCC version is 3.4.6.

Is there any known workaround for this kind of problem?

There is a big difference in speed between the optimized and unoptimized version of my program, so I really need to use optimizations.



This is my original functor. The one that works fine with no levels of optimizations and throws a segmentation fault with any level of optimization:
struct distanceToPointSort{
    indexedDocument* point ;
    distanceToPointSort(indexedDocument* p): point(p) {}
    bool operator() (indexedDocument* p1,indexedDocument* p2){
        return distance(point,p1) < distance(point,p2) ;
    }
} ;
And this one works flawlessly with any level of optimization:
struct distanceToPointSort{
    indexedDocument* point ;
    distanceToPointSort(indexedDocument* p): point(p) {}
    bool operator() (indexedDocument* p1,indexedDocument* p2){

        float d1=distance(point,p1) ;
        float d2=distance(point,p2) ;

        std::cout << "" ;  //without this line, I get a segmentation fault anyways

        return d1 < d2 ;
    }
} ;
Unfortunately, this problem is hard to reproduce because it happens with some specific values. I get the segmentation fault upon sorting just one out of more than a thousand vectors, so it really depends on the specific combination of values each vector has.
解决方案
Now that you posted the code fragment and a working workaround was found (@Windows programmer's answer), I can say that perhaps what you are looking for is -ffloat-store.

  
-ffloat-store
  
  
Do not store floating point variables in registers, and inhibit other options that might change whether a floating point value is taken from a register or memory.
  
  
This option prevents undesirable excess precision on machines such as the 68000 where the floating registers (of the 68881) keep more precision than a double is supposed to have. Similarly for the x86 architecture. For most programs, the excess precision does only good, but a few programs rely on the precise definition of IEEE floating point. Use -ffloat-store for such programs, after modifying them to store all pertinent intermediate computations into variables. 
Source: http://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Optimize-Options.html

                        
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