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The macro AC_TRY_CPP
is used to check whether particular header
files exist. You can check for one at a time, or more than one if you
need several header files to all exist for some purpose.
#include
statements and declarations,
on which shell variable, back quote, and backslash substitutions are
performed. (Actually, it can be any C program, but other statements are
probably not useful.) If the preprocessor produces no error messages
while processing it, run shell commands action-if-true. Otherwise
run shell commands action-if-false.
This macro uses CPPFLAGS
, but not CFLAGS
, because
@option{-g}, @option{-O}, etc. are not valid options to many C
preprocessors.
Here is how to find out whether a header file contains a particular
declaration, such as a typedef, a structure, a structure member, or a
function. Use AC_EGREP_HEADER
instead of running grep
directly on the header file; on some systems the symbol might be defined
in another header file that the file you are checking `#include's.
egrep
regular expression
pattern, execute shell commands action-if-found, otherwise
execute action-if-not-found.
To check for C preprocessor symbols, either defined by header files or
predefined by the C preprocessor, use AC_EGREP_CPP
. Here is an
example of the latter:
AC_EGREP_CPP(yes, [#ifdef _AIX yes #endif ], is_aix=yes, is_aix=no)
egrep
regular expression pattern, execute shell commands
action-if-found, otherwise execute action-if-not-found.
This macro calls AC_PROG_CPP
or AC_PROG_CXXCPP
(depending
on which language is current, see section Language Choice), if it hasn't
been called already.
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