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./configure always checks whether the build environment is sane...

I can't help but wonder what exactly a insane build environment is. What errors can this check raise?

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This comes from automake, specifically from its AM_SANITY_CHECK macro, which is called from AM_INIT_AUTOMAKE, which is normally called early in configure.ac. The gist of this macro is:

  • Check that the path to the source directory doesn't contain certain “unsafe” characters which can be hard to properly include in shell scripts makefiles.
  • Check that ls appears to work.
  • Check that a new file created in the build directory is newer than the configure file. If it isn't (typically because the clock on the build system is not set correctly), the build process is likely to fail because build processes usually rely on generated files having a more recent timestamp than the source files they are generated from.
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  • Why ls specifically? Is it only to test that basic executables are available and functional or is ls itself somehow used in the make process? Commented Apr 22, 2015 at 14:19
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    @terdon Some automake templates use ls. The AM_SANITY_CHECK macro itself uses ls to check the relative times of configure and a temporary file (it doesn't use test -nt because not all shells have it). Commented Apr 22, 2015 at 14:30

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