--without-v4l breaks configure script (with autoconf 2.71)

[fweimer-rh]

The configure.ac contains this:

if test "x$with_v4l" != "xno"; then
	AC_CHECK_HEADER(libv4l1-videodev.h,
		[AC_DEFINE(HAVE_LIBV4L1_VIDEODEV_H)],,)
	AC_CHECK_HEADER(linux/videodev.h,
		[AC_DEFINE(HAVE_LINUX_VIDEODEV_H)],,)
	AC_CHECK_HEADER(linux/videodev2.h,
		[AC_DEFINE(HAVE_LINUX_VIDEODEV2_H)],,)
fi

The first AC_CHECK_HEADER is where autoconf 2.71 chooses to inject all the system header probes. If --without-v4l is specified, these probes never run, and HAVE_SYS_STAT_H is not set. This causes the lstat check to go from

checking whether lstat correctly handles trailing slash... yes

to

checking whether lstat correctly handles trailing slash... no

because it no longer includes <sys/stat.h>.

I believe there is a rule that AC_CHECK_HEADER must not be called conditionally. I have asked about it on the autoconf list:

• Conditional AC_CHECK_HEADER

Related to:

• https://fedoraproject.org/wiki/Changes/PortingToModernC
• https://fedoraproject.org/wiki/Toolchain/PortingToModernC

[fweimer-rh]

Upstream for autoconf provided the following reference:

This macro should be used instead of plain if in code outside of an AC_DEFUN macro, when the contents of the if' use AC_REQUIRE` directly or indirectly (see Prerequisite Macros).

Common Shell Constructs