[PATCH] configure: Add new --enable-install-elfh option.

[Mark Wielaard <mark@klomp.org>]

We explicitly test (with system-elf-libelf) that our include headers
work with the system elf.h header. But it might be helpful to install
the elf.h file for a private install. Our elf.h header really is just
a copy of the latest glibc elf.h. But it might be newer and include
more constants than the system installed elf.h.

Add a new configure option --enable-install-elfh to install elf.h.
But warn when it is enabled for the default /usr or /usr/local prefix
because it might clash with the glibc/system elf.h header in that case.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 ChangeLog          |  4 ++++
 configure.ac       | 12 ++++++++++++
 libelf/ChangeLog   |  5 +++++
 libelf/Makefile.am | 13 ++++++++++---
 4 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 45418a0..148ce77 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2019-01-18  Mark Wielaard  <mark@klomp.org>
+
+	* configure.ac: Add new --enable-install-elfh.
+
 2018-07-04  Ross Burton <ross.burton@intel.com>
 
 	* configure.ac: Check for gawk.
diff --git a/configure.ac b/configure.ac
index b89b867..7d4e69d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -323,6 +323,11 @@ if test "$use_valgrind" = yes; then
 fi
 AM_CONDITIONAL(USE_VALGRIND, test "$use_valgrind" = yes)
 
+AC_ARG_ENABLE([install-elfh],
+AS_HELP_STRING([--enable-install-elfh],[install elf.h in include dir]),
+               [install_elfh=$enableval], [install_elfh=no])
+AM_CONDITIONAL(INSTALL_ELFH, test "$install_elfh" = yes)
+
 AM_CONDITIONAL(BUILD_STATIC, [dnl
 test "$use_gprof" = yes -o "$use_gcov" = yes])
 
@@ -658,6 +663,7 @@ AC_MSG_NOTICE([
 
   NOT RECOMMENDED FEATURES (should all be no)
     Experimental thread safety         : ${use_locks}
+    install elf.h                      : ${install_elfh}
 
   OTHER FEATURES
     Deterministic archives by default  : ${default_ar_deterministic}
@@ -673,3 +679,9 @@ AC_MSG_NOTICE([
     use rpath in tests                 : ${tests_use_rpath}
     test biarch                        : ${utrace_cv_cc_biarch}
 ])
+
+if test "$install_elfh" = yes; then
+  if test "${prefix}" = "/usr/local" -o "${prefix}" = "/usr"; then
+    AC_MSG_WARN([installing elf.h in ${includedir} might conflict with glibc/system elf.h])
+  fi
+fi
diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index 5783f0c..b89e93f 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,8 @@
+2019-01-18  Mark Wielaard  <mark@klomp.org>
+
+	* Makefile.am (INSTALL_ELFH): Add elf.h to include_HEADERS when
+	defined, otherwise (the default) add elf.h to noinst_HEADERS.
+
 2019-01-16  Mark Wielaard  <mark@klomp.org>
 
 	* note_xlate.h (elf_cvt_note): Check n_namesz and n_descsz don't
diff --git a/libelf/Makefile.am b/libelf/Makefile.am
index ddaeaa2..d5d63f7 100644
--- a/libelf/Makefile.am
+++ b/libelf/Makefile.am
@@ -39,6 +39,16 @@ noinst_LIBRARIES = libelf_pic.a
 noinst_PROGRAMS = $(noinst_LIBRARIES:_pic.a=.so)
 include_HEADERS = libelf.h gelf.h nlist.h
 
+noinst_HEADERS = abstract.h common.h exttypes.h gelf_xlate.h libelfP.h \
+		 version_xlate.h gnuhash_xlate.h note_xlate.h dl-hash.h \
+		 chdr_xlate.h
+
+if INSTALL_ELFH
+include_HEADERS += elf.h
+else
+noinst_HEADERS += elf.h
+endif
+
 pkginclude_HEADERS = elf-knowledge.h
 
 libelf_a_SOURCES = elf_version.c elf_hash.c elf_error.c elf_fill.c \
@@ -123,9 +133,6 @@ uninstall: uninstall-am
 	rm -f $(DESTDIR)$(libdir)/libelf.so.$(VERSION)
 	rm -f $(DESTDIR)$(libdir)/libelf.so
 
-noinst_HEADERS = elf.h abstract.h common.h exttypes.h gelf_xlate.h libelfP.h \
-		 version_xlate.h gnuhash_xlate.h note_xlate.h dl-hash.h \
-		 chdr_xlate.h
 EXTRA_DIST = libelf.map
 
 CLEANFILES += $(am_libelf_pic_a_OBJECTS) libelf.so.$(VERSION)
-- 
1.8.3.1