The following macros check for operating system services or capabilities.
If either or both were not given, get the missing values by running
xmkmf(or an executable pointed to by the
XMKMFenvironment variable) on a trivial Imakefile and examining the makefile that it produces. Setting
XMKMFto ‘false’ disables this method.
If this method fails to find the X Window System, configure looks for the files in several directories where they often reside. If either method is successful, set the shell variables
x_librariesto their locations, unless they are in directories the compiler searches by default.
If both methods fail, or the user gave the command line option --without-x, set the shell variable
no_xto ‘yes’; otherwise set it to the empty string.
This macro also checks for special libraries that some systems need in order to compile X programs. It adds any that the system needs to output variable
X_EXTRA_LIBS. And it checks for special X11R6 libraries that need to be linked with before -lX11, and adds any found to the output variable
Arrange for 64-bit file offsets, known as large-file support. On some hosts, one must use special compiler options to build programs that can access large files. Append any such options to the output variable
Large-file support can be disabled by configuring with the --disable-largefile option.
If you use this macro, check that your program works even when
off_tis wider than
long int, since this is common when large-file support is enabled. For example, it is not correct to print an arbitrary
printf ("%ld", (long int) X).
The LFS introduced the
ftellofunctions to replace their C counterparts
ftellthat do not use
off_t. Take care to use
AC_FUNC_FSEEKOto make their prototypes available when using them and large-file support is enabled.