/[autoconf]/autoconf/doc/autoconf.texi
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revision 1.724 by eggert, Fri Mar 7 19:21:36 2003 UTC revision 1.725 by eggert, Sun Mar 23 10:21:43 2003 UTC
# Line 14659  not fully exploited}, and eight times sl Line 14659  not fully exploited}, and eight times sl
14659  @node Present But Cannot Be Compiled  @node Present But Cannot Be Compiled
14660  @section Header Present But Cannot Be Compiled  @section Header Present But Cannot Be Compiled
14661    
14662  The most important guideline to bare in mind when checking for  The most important guideline to bear in mind when checking for
14663  features is to mock as much as possible the intended use.  features is to mimic as much as possible the intended use.
14664  Unfortunately, old versions of @code{AC_CHECK_HEADER} and  Unfortunately, old versions of @code{AC_CHECK_HEADER} and
14665  @code{AC_CHECK_HEADERS} failed to follow this idea, and used to call  @code{AC_CHECK_HEADERS} failed to follow this idea, and called
14666  the preprocessor, instead of the compiler, to check for headers.  As a  the preprocessor, instead of the compiler, to check for headers.  As a
14667  result, incompatibilities between headers went unnoticed during  result, incompatibilities between headers went unnoticed during
14668  configuration, and maintainers finally had to deal with this issue  configuration, and maintainers finally had to deal with this issue
14669  elsewhere.  elsewhere.
14670    
14671  Since Autoconf 2.56 both checks are performed, and @code{configure}  As of Autoconf 2.56 both checks are performed, and @code{configure}
14672  complains loudly if the compiler and the preprocessor do not agree.  complains loudly if the compiler and the preprocessor do not agree.
14673  For the time being the result is that of the preprocessor, so that  For the time being the result used is that of the preprocessor, to give
14674  maintainers can adjust their @file{configure.ac}, but in the near  maintainers time to adjust their @file{configure.ac}, but in the near
14675  future, the compiler only will be considered.  future, only the compiler will be considered.
14676    
14677  Consider the following example:  Consider the following example:
14678    

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