+ - libgc, at least version 7.0
+
+ libgc (aka. the Boehm-Demers-Weiser garbage collector) is the
+ conservative garbage collector used by Guile. It is available
+ from http://www.hpl.hp.com/personal/Hans_Boehm/gc/ .
+
+ - libffi
+
+ libffi provides a "foreign function interface", used by the
+ `(system foreign)' module. It is available from
+ http://sourceware.org/libffi/ .
+
+ - pkg-config
+
+ Guile's ./configure script uses pkg-config to discover the correct
+ compile and link options for libgc and libffi. For this to work,
+ the `PKG_CONFIG_PATH' environment variable must be set to point to
+ the places where libgc's and libffi's `.pc' files can be found:
+
+ PKG_CONFIG_PATH=/path/to/libgc/lib/pkgconfig:/path/to/libffi/lib/pkgconfig
+
+ Alternatively, when pkg-config is not installed, you can work around
+ this by setting some variables as part of the configure
+ command-line:
+
+ - PKG_CONFIG=true
+
+ - BDW_GC_CFLAGS=<compile flags for picking up libgc headers>
+
+ - BDW_GC_LIBS=<linker flags for picking up the libgc library>
+
+ Note that because you're bypassing all pkg-config checks, you will
+ also have to specify libffi flags as well:
+
+ - LIBFFI_CFLAGS=<compile flags for picking up libffi headers>
+
+ - LIBFFI_LIBS=<linker flags for picking up the libffi library>
+