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Asked: 2026-05-19T13:09:52+00:00

I am having a problem with a configure script verifying the presence of some

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I am having a problem with a configure script verifying the presence of some basic functions, 

AC_CHECK_FUNCS([floor gettimeofday memset pow sqrt sin exp])

Under certain criteria, the results are expected (checking for x... yes). Otherwise the math functions above are claimed to be not defined. The difference is a call to verify some lapack routines first. These are checked by, AC_CHECK_LIB([lapack],[dsyev_],.... If these checks are not done first, then the above math functions fail to check (final compilation works).

I’ve reduced the configure script to the following that recreates the issue,

AC_INIT([TEST], [0.0], [none@none.com])
#AC_CHECK_LIB([lapack],[dsyev_], , AC_MSG_FAILURE([Missing lapack]))
AC_CHECK_FUNCS([floor gettimeofday memset pow sqrt sin exp])

Uncommenting the second line results in proper visual results. I imagine that the math library isn’t included or checked for some reason. In fact, AC_CHECK_LIB([m],[exp]) works fine.

What’s the cause of this, and what is the proper way to use this directive? What kind of x-platform considerations should I observe?

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1 Answer

  1. Editorial Team

    The math functions are in the math library, so if you want them, you need to pull the math library into the link arguments that configure uses. AC_CHECK_LIB([m],[exp]) is one way to do that. The reason that AC_CHECK_LIB([lapack],...) also has that effect is that it quite probably pulls in -lm itself (not knowing the library, but I read it’s for linear algebra).

    I suggest that you avoid AC_CHECK_LIB and instead use AC_SEARCH_LIBS for functions that are potentially not in the standard C library. So

    AC_SEARCH_LIBS(exp, m)
AC_SEARCH_LIBS(dsyev_, lapack)

    (But using AC_CHECK_LIB is not actually wrong.)

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