(autoconf.info)Test Programs

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5.4.1 Running Test Programs
---------------------------

Use the following macro if you need to test run-time behavior of the
system while configuring.

 -- Macro: AC_TRY_RUN (PROGRAM, [ACTION-IF-TRUE [, ACTION-IF-FALSE [,
          ACTION-IF-CROSS-COMPILING]]])
     PROGRAM is the text of a C program, on which shell variable and
     backquote substitutions are performed.  If it compiles and links
     successfully and returns an exit status of 0 when executed, run
     shell commands ACTION-IF-TRUE.  Otherwise run shell commands
     ACTION-IF-FALSE; the exit status of the program is available in the
     shell variable '$?'.  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.

   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 (Note: Manual
Configuration).  Alternatively, set up a test results cache file with
the correct values for the target system (Note: 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.

 -- Macro: AC_C_CROSS
     This macro is obsolete; it does nothing.