Provide Makefile variables LIBEVENT_{CFLAGS,CPPFLAGS,LDFLAGS}

This will allow a parent package to specify compiler, CPP, and linker
flags to a libevent built as a sub-package. Document this in
whatsnew-2.2.txt.

Picked-from: #506
Closes: #506

diff --git a/Makefile.am b/Makefile.am
index 2353976791b8a582fe4b3c537f96017d16d98030..902d5c19ded03b1fd097f401d4e1550f42db4b13 100644 (file)
--- a/Makefile.am
+++ b/Makefile.am
@@ -231,7 +231,11 @@ NO_UNDEFINED =
 MAYBE_CORE =
 endif
 
-GENERIC_LDFLAGS = -version-info $(VERSION_INFO) $(RELEASE) $(NO_UNDEFINED)
+AM_CFLAGS = $(LIBEVENT_CFLAGS)
+AM_CPPFLAGS = -I$(srcdir)/compat -I$(srcdir)/include -I./include $(SYS_INCLUDES) $(LIBEVENT_CPPFLAGS)
+AM_LDFLAGS = $(LIBEVENT_LDFLAGS)
+
+GENERIC_LDFLAGS = -version-info $(VERSION_INFO) $(RELEASE) $(NO_UNDEFINED) $(AM_LDFLAGS)
 
 libevent_la_SOURCES = $(CORE_SRC) $(EXTRAS_SRC)
 libevent_la_LIBADD = @LTLIBOBJS@ $(SYS_LIBS)
@@ -302,8 +306,6 @@ else
 noinst_HEADERS += $(EVENT1_HDRS)
 endif
 
-AM_CPPFLAGS = -I$(srcdir)/compat -I$(srcdir)/include -I./include $(SYS_INCLUDES)
-
 verify: check
 
 doxygen: FORCE

diff --git a/whatsnew-2.2.txt b/whatsnew-2.2.txt
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..7e09e61f8204193673a41095ff6e371c9549a180 100644 (file)
--- a/whatsnew-2.2.txt
+++ b/whatsnew-2.2.txt
@@ -0,0 +1,50 @@
+...
+
+* Building libevent as a sub-project using GNU Auto* tools
+
+Some projects will choose to include libevent in their source distribution,
+and build libevent as a sub-project.  This may be effected by putting the
+line:
+
+ AC_CONFIG_SUBDIRS([path/to/libevent])
+
+in the master configure.ac file for the master project.
+
+There are cases where the master project will want to pass in additional
+flags for CFLAGS, CPPFLAGS, or LDFLAGS.  Since these variables are reserved
+for the user, and AM_CFLAGS, AM_CPPFLAGS, and AM_LDFLAGS are reserved for
+each package, libevent offers the following variables for a master package
+to tell libevent that there are additional compile/link values:
+
+ LIBEVENT_CFLAGS
+ LIBEVENT_CPPFLAGS
+ LIBEVENT_LDFLAGS
+
+A master package can set these variables in its configure.ac file.
+
+Here's an example:
+
+configure.ac:
+...
+EXTRA_CFLAGS=...
+EXTRA_CPPFLAGS=...
+EXTRA_LDFLAGS=...
+...
+dnl ac_configure_args is undocumented but widely abused, as here,
+dnl to modify the defaults of the libevent subpackage, by prefixing
+dnl our changes to the child configure arguments already assembled.
+dnl User-supplied contradictory choices should prevail thanks to
+dnl "last wins".
+ac_configure_args=" --disable-openssl${ac_configure_args}"
+ac_configure_args=" --disable-shared${ac_configure_args}"
+ac_configure_args=" --disable-libevent-regress${ac_configure_args}"
+ac_configure_args=" --disable-libevent-install${ac_configure_args}"
+ac_configure_args=" --enable-silent-rules${ac_configure_args}"
+ac_configure_args=" --enable-function-sections${ac_configure_args}"
+ac_configure_args=" LIBEVENT_CFLAGS='${EXTRA_CFLAGS}'${ac_configure_args}"
+ac_configure_args=" LIBEVENT_CPPFLAGS='${EXTRA_CPPFLAGS}'${ac_configure_args}"
+ac_configure_args=" LIBEVENT_LDFLAGS='${EXTRA_LDFLAGS}'${ac_configure_args}"
+AC_CONFIG_SUBDIRS([libevent])
+...
+
+The space after the initial '"' is significant.
\ No newline at end of file