Problem with calling lapack_make_complex_{float,double} with C/C++-优快云博客

本文介绍了一个在C++中使用LAPACK库进行复数运算时出现的异常问题及解决方案。作者通过编写简单的测试例发现，使用lapack_make_complex_double函数创建复数时会导致程序崩溃。为解决该问题，作者自行编写了make_complex函数来替代，并成功解决了异常问题。

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I wrote a simple test routine:

for(int i = 0; i < 100;++i)
 {
  std::cout<< "i="<< i <<": ";
  print_complex(lapack_make_complex_double(1,0));
  std::cout<< std::endl;
 }

where print_complex prints the complex to console.

The routine will end with an exception:

First-chance exception at 0x00420fd0 in LTELinkLevelSimulator.exe: 0xC0000005: Access violation reading location 0x00000000.
Unhandled exception at 0x770b15de in LTELinkLevelSimulator.exe:0xC0000005: Access violation reading location 0x00000000.

and the printed complexes on the console are:

See, something goes wrong. The complex should be 1+0j, but the lapack_make_complex_double function, which is a C interface to create a complex with double precision, is not stable.

I have to write my own make_complex routine instead. It looks like:

lapack_complex_double make_complex(constdouble a, const double b)
{
 lapack_complex_double c;
 c.real = a;
 c.imag = b;

 return c;
}

If replace the lapack_make_complex_double with make_complex, the output is:

No error happens again!

One last word, when using the CBLAS and LAPACKE library in your C/C++ code, be very careful of such flaws.