Change library ordering when testing for library availability with autoconf

As discussed in #371, the order in which libraries must be listed on the
compiler command-line has changed in recent versions of GCC, in order for
linking to succeed. This is because the `--as-needed` option has become
enabled by default:
https://sigquit.wordpress.com/2011/02/16/why-asneeded-doesnt-work-as-expected-for-your-libraries-on-your-autotools-project

A succinct explanation of the required changes in library-ordering from
https://wiki.ubuntu.com/NattyNarwhal/ToolchainTransition by way of
https://stackoverflow.com/a/69795683:

> "The --as-needed option also makes the linker sensitive to the ordering
> of libraries on the command-line. You may need to move some libraries
> later in the command-line, so they come after other libraries or files
> that require symbols from them." [3]

It appears that both Debian-based and Fedora-based distributions are moving
towards this as the new default behavior:

- https://wiki.debian.org/ToolChain/DSOLinking (Debian)
- http://fedoraproject.org/wiki/UnderstandingDSOLinkChange (Fedora)

Signed-off-by: Daniel Lenski <dlenski@gmail.com>

diff --git a/configure.ac b/configure.ac
index a0210929b77dc2d92171d7d716960e5b80c478c2..6b7a6555fbda6ec12dd9dcec3468c8a11c15ae8b 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -340,7 +340,7 @@ if test "$USE_NLS" = "yes"; then
     [AC_MSG_RESULT(yes)],
     [AC_LIB_LINKFLAGS_BODY([intl])
      oldLIBS="$LIBS"
-     LIBS="$LIBS $LIBINTL"
+     LIBS="$LIBINTL $LIBS"
      oldCFLAGS="$LIBS"
      CFLAGS="$CFLAGS $INCINTL"
      AC_LINK_IFELSE([AC_LANG_PROGRAM([
@@ -406,7 +406,7 @@ if test "$ssl_library" = ""; then
     elif test "$with_openssl" = "yes" -o "$with_openssl" = ""; then
         PKG_CHECK_MODULES(OPENSSL, openssl, [AC_SUBST(SSL_PC, [openssl])],
            [oldLIBS="$LIBS"
-            LIBS="$LIBS -lssl -lcrypto"
+            LIBS="-lssl -lcrypto $LIBS"
             AC_MSG_CHECKING([for OpenSSL without pkg-config])
             AC_LINK_IFELSE([AC_LANG_PROGRAM([
                                #include <openssl/ssl.h>
@@ -471,7 +471,7 @@ case "$ssl_library" in
     OpenSSL)
        oldLIBS="${LIBS}"
        oldCFLAGS="${CFLAGS}"
-       LIBS="${LIBS} ${OPENSSL_LIBS}"
+       LIBS="${OPENSSL_LIBS} ${LIBS}"
        CFLAGS="${CFLAGS} ${OPENSSL_CFLAGS}"
 
        # Check for the various known-broken versions of OpenSSL, which includes LibreSSL.
@@ -592,7 +592,7 @@ perhaps consider building with GnuTLS instead.)])
     GnuTLS)
        oldlibs="$LIBS"
        oldcflags="$CFLAGS"
-       LIBS="$LIBS $GNUTLS_LIBS"
+       LIBS="$GNUTLS_LIBS $LIBS"
        CFLAGS="$CFLAGS $GNUTLS_CFLAGS"
        esp=yes
        dtls=yes
@@ -621,7 +621,7 @@ perhaps consider building with GnuTLS instead.)])
                                          pkcs11_support=GnuTLS
                                          AC_SUBST(P11KIT_PC, p11-kit-1)],
                                         [:])], [])
-       LIBS="$oldlibs -ltspi"
+       LIBS="-ltspi $oldlibs"
        AC_MSG_CHECKING([for Trousers tss library])
        AC_LINK_IFELSE([AC_LANG_PROGRAM([
                                           #include <trousers/tss.h>
@@ -796,7 +796,7 @@ PKG_CHECK_MODULES([LIBLZ4], [liblz4], [
        AC_DEFINE([HAVE_LZ4], [], [LZ4 was found])
        lz4_pkg=yes
        oldLIBS="$LIBS"
-       LIBS="$LIBS $LIBLZ4_LIBS"
+       LIBS="$LIBLZ4_LIBS $LIBS"
        oldCFLAGS="$CFLAGS"
        CFLAGS="$CFLAGS $LIBLZ4_CFLAGS"
        AC_MSG_CHECKING([for LZ4_compress_default()])
@@ -863,7 +863,7 @@ AM_CONDITIONAL(BUILTIN_JSON, [test "$json" = "builtin"])
 
 PKG_CHECK_MODULES(ZLIB, zlib, [AC_SUBST(ZLIB_PC, [zlib])],
                  [oldLIBS="$LIBS"
-                 LIBS="$LIBS -lz"
+                 LIBS="-lz $LIBS"
                  AC_MSG_CHECKING([for zlib without pkg-config])
                  AC_LINK_IFELSE([AC_LANG_PROGRAM([
                   #include <zlib.h>],[
@@ -893,7 +893,7 @@ dnl libproxy.h in that case.
 if (test "$libproxy_pkg" = "no"); then
    AC_MSG_CHECKING([for libproxy])
    oldLIBS="$LIBS"
-   LIBS="$LIBS -lproxy"
+   LIBS="-lproxy $LIBS"
    AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <libproxy.h>],
                           [(void)px_proxy_factory_new();])],
          [AC_MSG_RESULT(yes (with libproxy.h))