automake zlib configuration check is broken in FreeBSD

[missionsix]

The following configure error happens on trunk.

build% ../Transmission/autogen.sh --disable-nls
creating libtransmission/version.h
libtoolize: putting auxiliary files in `.'.
libtoolize: copying file `./ltmain.sh'
libtoolize: putting macros in AC_CONFIG_MACRO_DIR, `m4'.
libtoolize: copying file `m4/libtool.m4'
libtoolize: copying file `m4/ltoptions.m4'
libtoolize: copying file `m4/ltsugar.m4'
libtoolize: copying file `m4/ltversion.m4'
libtoolize: copying file `m4/lt~obsolete.m4'
Creating aclocal.m4 ...
Running glib-gettextize...  Ignore non-fatal messages.
Copying file po/Makefile.in.in

...

checking pkg-config is at least version 0.9.0... yes
checking for OPENSSL... no
checking for OpenSSL... /usr
checking for LIBCURL... yes
checking for LIBEVENT... yes

checking for ZLIB... configure: error: Package requirements (zlib >= 1.2.3) were not met:

Package zlib was not found in the pkg-config search path.
Perhaps you should add the directory containing `zlib.pc'
to the PKG_CONFIG_PATH environment variable
Package 'zlib', required by 'world', not found

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.

Alternatively, you may set the environment variables ZLIB_CFLAGS
and ZLIB_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.

zlib is not part of pkg-config on FreeBSD.

It's part of the base distribution, and as such, CHECK_MODULES will fail to find zlib.

PKG_CHECK_MODULES(ZLIB, [zlib >= $ZLIB_MINIMUM])

The proposed solution is to failback to a lib check if the zlib module is not found in pkg-config.

Checking for libz and zlib.h check will be sufficient in making sure the system has zlib.

Some care was taken to preserve the version check with in the failback case.

[missionsix]

Proposed patch:

--- a/configure.ac
+++ b/configure.ac
@@ -115,7 +115,24 @@ AC_SEARCH_LIBS([quotacursor_skipidtype], [quota])
 PKG_CHECK_MODULES(OPENSSL, [openssl >= $OPENSSL_MINIMUM], , [CHECK_SSL()])
 PKG_CHECK_MODULES(LIBCURL, [libcurl >= $CURL_MINIMUM])
 PKG_CHECK_MODULES(LIBEVENT, [libevent >= $LIBEVENT_MINIMUM])
-PKG_CHECK_MODULES(ZLIB, [zlib >= $ZLIB_MINIMUM])
+PKG_CHECK_MODULES(ZLIB, [zlib >= $ZLIB_MINIMUM], [found_zlib=yes], [found_zlib=no])
+if test "x$found_zlib" = "xno" ; then
+   AC_CHECK_LIB(z, inflate,
+       [AC_CHECK_HEADER([zlib.h],
+       [AC_COMPILE_IFELSE(
+           [AC_LANG_PROGRAM([[
+               #include <zlib.h>
+               #if !defined(ZLIB_VERNUM) || (ZLIB_VERNUM < 0x1230)
+               // compile error
+               #endif
+          ]],[])],
+          [found_zlib=yes])])])
+   if test "x$found_zlib" = "xno" ; then
+      AC_MSG_ERROR([Working zlib library and headers not found])
+   fi
+   ZLIBS_LIBS='-z'
+   AC_SUBST(ZLIB_LIBS)
+fi

[missionsix]

Patch file to failback to lib check if pkg-config fails

[missionsix]

The issue was introduced by this well intentioned commit:

https://trac.transmissionbt.com/changeset/14323/

[mike.dld]

Should it be ZLIBS_LIBS='-lz' instead?