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Use the following macro if you need to test run-time behavior of the system while configuring.
This macro double quotes program, the text of a program in the
current language (see section 6.7 Language Choice), on which shell variable and
back quote substitutions are performed. This macro uses CFLAGS
or CXXFLAGS
, CPPFLAGS
, LDFLAGS
, and LIBS
when compiling.
If the C compiler being used does not produce executables that run on
the system where configure
is being run, then the test program is
not run. If the optional shell commands action-if-cross-compiling
are given, they are run instead. Otherwise, configure
prints
an error message and exits.
In the action-if-false section, the exit status of the program is available in the shell variable `$?', but be very careful to limit yourself to positive values smaller than 127; bigger values shall be saved into a file by the program. Note also that you have simply no guarantee that this exit status is issued by the program, or by the failure of its compilation. In other words, use this feature if sadist only, it was reestablished because the Autoconf maintainers grew tired of receiving "bug reports".
Try to provide a pessimistic default value to use when cross-compiling
makes run-time tests impossible. You do this by passing the optional
last argument to AC_TRY_RUN
. autoconf
prints a warning
message when creating configure
each time it encounters a call to
AC_TRY_RUN
with no action-if-cross-compiling argument
given. You may ignore the warning, though users will not be able to
configure your package for cross-compiling. A few of the macros
distributed with Autoconf produce this warning message.
To configure for cross-compiling you can also choose a value for those parameters based on the canonical system name (see section 11. Manual Configuration). Alternatively, set up a test results cache file with the correct values for the host system (see section 7.3 Caching Results).
To provide a default for calls of AC_TRY_RUN
that are embedded in
other macros, including a few of the ones that come with Autoconf, you
can call AC_PROG_CC
before running them. Then, if the shell
variable cross_compiling
is set to `yes', use an alternate
method to get the results instead of calling the macros.
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