c++ - 避免 .oct 函数中的段错误？

Question

这主要针对Octave的用户。

在 Octave 的 c++ API 文档中，其中一个示例是将两个矩阵相加的函数，如下所示:

*/addtwomatrices.cc
#include <octave/oct.h>
DEFUN_DLD (addtwomatrices, args, , "Add A to B")
{
  if (args.length () != 2)
    print_usage ();

  NDArray A = args(0).array_value ();
  NDArray B = args(1).array_value ();

 return octave_value (A + B);
}

链接:https://www.gnu.org/software/octave/doc/interpreter/Matrices-and-Arrays-in-Oct_002dFiles.html#Matrices-and-Arrays-in-Oct_002dFiles

它工作正常并且编译没有错误。但是，在 Octave 中使用它时，如果使用错误数量的参数调用该函数，它会出现错误并退出程序并转储 octave-core。

即使使用错误数量的参数调用此函数，是否有办法保持 Octave 打开？例如，

addtwomatrices(5)
octave 1> "Incorrect Number of Arguments Supplied. Please provide 2."
octave 2>'

代替

Invalid call to addtwomatrices.  Correct usage is:

Adds 2 matrices
Additional help for built-in functions and operators is
available in the on-line version of the manual.  Use the command
`doc <topic>' to search the manual index.

Help and information about Octave is also available on the WWW
at http://www.octave.org and via the help@octave.org
mailing list.
panic: Segmentation fault -- stopping myself...
attempting to save variables to `octave-core'...
save to `octave-core' complete
Segmentation fault

Answer 1

您正在阅读最新版 Octave (4.2.1) 的在线手册，但您没有使用 Octave 4.2.1。您需要查看 Octave 版本的文档:

• Documentation for "Matrices and Arrays in Oct-Files" in Octave 4.0.3
• Documentation for "Matrices and Arrays in Oct-Files" in Octave 4.2.1

如果您使用的是 Octave 4.2.X 版本，那么它会按您的预期运行:

$ cat addtwomatrices.cc 
#include <octave/oct.h>
DEFUN_DLD (addtwomatrices, args, , "Add A to B")
{
  if (args.length () != 2)
    print_usage ();

  NDArray A = args(0).array_value ();
  NDArray B = args(1).array_value ();

 return octave_value (A + B);
}
$ mkoctfile-4.2.1 addtwomatrices.cc 
$ octave-cli-4.2.1 -q
octave-cli-4.2.1:1> addtwomatrices (5)
error: Invalid call to addtwomatrices.  Correct usage is:

Add A to B
octave-cli-4.2.1:1>
$ mkoctfile-4.0.0 addtwomatrices.cc 
$ octave-cli-4.0.0 -q
octave-cli-4.0.0:1> addtwomatrices (5)
error: Invalid call to addtwomatrices.  Correct usage is:

Add A to B
panic: Segmentation fault -- stopping myself...
Segmentation fault

Octave 的 libinterp 中处理错误的方式在 4.2 中发生了变化。如果您使用的是旧版本，您需要自己处理函数的返回。你应该这样做:

#include <octave/oct.h>
DEFUN_DLD (addtwomatrices, args, , "Add A to B")
{
  if (args.length () != 2)
    {
      print_usage ();
      // In octave 4.2, print_usage also throws exceptions
      // and exist the function.  This is the same behaviour
      // in Octave m language.  In Octave 4.0, it only prints
      // the usage and then you still need to return otherwise
      // it continues execution of the function.
      return octave_value (); 
    }

  NDArray A = args(0).array_value ();
  NDArray B = args(1).array_value ();

 return octave_value (A + B);
}