这个import_umath函数是什么? [英] What is this import_umath function?

问题描述

当编译一堆由Cython生成的与Numpy接口的C文件时，我得到警告:

When compiling a bunch of Cython-generated C files that interface with Numpy, I get the warning:

/usr/lib/pymodules/python2.7/numpy/core/include/numpy/__ufunc_api.h:226:1: warning: ‘_import_umath’ defined but not used [-Wunused-function]

我似乎无法摆脱这一点.弄清楚这可能类似于np.import_array()，它摆脱了相关警告(实际上是必填 (使用Numpy C API)，我在顶层尝试了np.import_umath()，但警告仍然存在.我如何摆脱它?

I can't seem to get rid of that. Figuring this might be similar to np.import_array(), which gets rid of a related warning (and is actually required for using the Numpy C API), I tried np.import_umath() at top level, but the warning persists. How do I get rid of it?

(Cython 0.17.4，Numpy 1.6.2.)

(Cython 0.17.4, Numpy 1.6.2.)

推荐答案

有一个 Cython邮件列表上的主题，对此进行了一些讨论.我相信讨论是关于Cython测试套件的，但是我认为相同的想法也可以应用于生成的文件.

There's a thread on the Cython mailing list that discusses this a little bit. I believe that the discussion was concerning the Cython test suite, but I think the same ideas can be applied to generated files.

从本质上讲，该问题涉及黑客攻击，目的是避免C编译器有关未使用功能的警告.

In essence, the issue involved a hack that was done in order to avoid C compiler warnings about unused functions.

相关代码文件当前如下所示:

cdef extern from *:
   bint FALSE "0"
   void import_array()
#   void import_umath()

if FALSE:
    import_array()
#    import_umath()

过去，import_umath()部分没有注释，但事实证明，在C ++模式下构建时会导致错误.因此，似乎已决定，编译器警告比破碎的构建.

In the past, the import_umath() portions were uncommented, but as it turns out, this was causing errors when building in C++ mode. So it appears that it was decided that a compiler warning is much better than a broken build.

简而言之，看来此特殊警告是出于C ++兼容性的考虑而存在的，可以安全地忽略.我想如果您真的不喜欢它，并且如果您在C模式下构建，那么您可以尝试通过导入类似的.pxi文件并调用import_umath()来进行相同的破解.在您的Cython代码中.

In short, it seems this particular warning exists for the sake of C++ compatibility, and can be safely ignored. I suppose if you really dislike it, and if you're building in C mode, then you could try to do the same hack, by importing a similar .pxi file with a call to import_umath() inside of your Cython code.

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