build: lib target now builds a shared library.

A new 'LIBRARY' variable also causes the libraries to be installed
along the headers and a newly introduced pkg-config file.

* Makefile (DEFAULT) [LIBRARY]: Add lib to it.
(strip_prefix, simplify_pkgconf_dir): New macros.
(prefix, exec_prefix, includedir, bindir, libdir, datadir)
(PKGCONF_EXEC_PREFIX, PKGCONF_INCLUDEDIR, PKGCONF_LIBDIR): New
variables.
(CFLAGS): Add -fPIC.
(PKGCONF_DIR, LIB_STATIC, LIB_SHARED, PKGCONF_FILE): New variables.
(lib): Express target via LIB_STATIC and LIB_SHARED; add
$(PKGCONF_FILE).
(install_lib, install_headers, install_pkgconf_file): New macros.
(install) [LIBRARY]: Conditionally add lib and pkgconf targets, as
well as associated recipes. Adjust installation paths to use new variabes.
($(LIBDIR)/libsameboy.so, PKGCONF_FILE, pkgconf): New targets.
(.PHONY): Register pkgconf. Add missing space between lib/lib-unsupported
* README.md: Update doc.
* sameboy.pc.in: New file.

Makefile

@@ -33,11 +33,34 @@ else
 DEFAULT := sdl
 endif
 
+ifneq ($(LIBRARY),)
+DEFAULT += lib
+endif
+
 NULL := /dev/null
 ifeq ($(PLATFORM),windows32)
 NULL := NUL
 endif
 
+# Strip a given prefix from a string.
+# arg1: The prefix to strip.
+# arg2: The text containing the prefix.
+# Return $text with $prefix stripped, else nothing.
+define strip_prefix =
+$(let stripped,$(subst $(1),,$(2)),$\
+  $(shell test "$(1)$(stripped)" = "$(2)" && echo $(stripped)))
+endef
+
+# Simplify a path for use with pkg-config, by replacing $prefix with '${prefix}'
+# arg1: prefix, e.g. an installation prefix, such as /usr/local.
+# arg2: pkgdir, e.g. a path such as $datadir, $bindir, etc.
+# arg3: pkg-config variable name, e.g. 'prefix' or 'exec_prefix'.
+#       Defaults to 'prefix'.
+define simplify_pkgconf_dir =
+$(let stripped,$(call strip_prefix,$(1),$(2)),$\
+  $(if stripped,$${$(or $(3),prefix)}$(stripped),$(2)))
+endef
+
 ifneq ($(shell which xdg-open 2> $(NULL))$(FREEDESKTOP),)
 # Running on an FreeDesktop environment, configure for (optional) installation
 DESTDIR ?= 
@@ -46,8 +69,26 @@ DATA_DIR ?= $(PREFIX)/share/sameboy/
 FREEDESKTOP ?= true
 endif
 
+# Autoconf-style conventionally named variables.
+prefix ?= $(PREFIX)
+exec_prefix ?= $(prefix)
+includedir ?= $(prefix)/include
+bindir ?= $(exec_prefix)/bin
+libdir ?= $(exec_prefix)/lib
+datadir ?= $(prefix)/share
+
+# Prettified variants for use in the pkg-config file.
+override PKGCONF_EXEC_PREFIX = \
+	$(call simplify_pkgconf_dir,$(prefix),$(exec_prefix))
+override PKGCONF_INCLUDEDIR = \
+	$(call simplify_pkgconf_dir,$(prefix),$(includedir))
+override PKGCONF_LIBDIR = \
+	$(call simplify_pkgconf_dir,$(exec_prefix),$(libdir),exec_prefix)
+
 default: $(DEFAULT)
 
+CFLAGS += -fPIC			# required for the shared library
+
 ifeq ($(MAKECMDGOALS),)
 MAKECMDGOALS := $(DEFAULT)
 endif
@@ -111,6 +152,10 @@ BIN := build/bin
 OBJ := build/obj
 INC := build/include/sameboy
 LIBDIR := build/lib
+PKGCONF_DIR := $(LIBDIR)/pkgconfig
+LIB_STATIC := $(LIBDIR)/libsameboy.a
+LIB_SHARED := $(LIBDIR)/libsameboy.so
+PKGCONF_FILE := $(PKGCONF_DIR)/sameboy.pc
 
 BOOTROMS_DIR ?= $(BIN)/BootROMs
 
@@ -376,10 +421,17 @@ _ios: $(BIN)/SameBoy-iOS.app $(OBJ)/installer
 ios-ipa: $(BIN)/SameBoy-iOS.ipa
 ios-deb: $(BIN)/SameBoy-iOS.deb
 ifeq ($(PLATFORM),windows32)
+
+# Libraries.
 lib: lib-unsupported
-else
-lib: $(LIBDIR)/libsameboy.o $(LIBDIR)/libsameboy.a
+else ifeq ($(LIBRARY), shared)
+lib: $(LIB_SHARED) $(PKGCONF_FILE)
+else ifeq ($(LIBRARY), static)
+lib: $(LIBDIR)/libsameboy.o $(LIB_STATIC)
+else ifneq ($(LIBRARY),)
+lib: $(LIBDIR)/libsameboy.o $(LIB_STATIC) $(LIB_SHARED) $(PKGCONF_FILE)
 endif
+
 all: sdl tester libretro lib
 ifeq ($(PLATFORM),Darwin)
 all: cocoa ios-ipa ios-deb
@@ -723,12 +775,32 @@ libretro:
 	CC=$(CC) CFLAGS="$(WARNINGS)" $(MAKE) -C libretro BOOTROMS_DIR=$(abspath $(BOOTROMS_DIR)) BIN=$(abspath $(BIN))
 
 # Install for Linux, and other FreeDesktop platforms.
+install_lib = install -Dm 644 -t $(DESTDIR)$(libdir) $(1)
+install_headers = install -Dm 644 -t $(DESTDIR)$(includedir)/sameboy $(INC)/*
+install_pkgconf_file = install -Dm 644 -t $(DESTDIR)$(libdir)/pkgconfig $(PKGCONF_FILE)
+
 ifneq ($(FREEDESKTOP),)
+ifneq ($(LIBRARY),)
+install: lib pkgconf
+endif
 install: $(BIN)/XdgThumbnailer/sameboy-thumbnailer sdl $(shell find FreeDesktop) XdgThumbnailer/sameboy.thumbnailer
 	(cd $(BIN)/SDL && find . \! -name sameboy -type f -exec install -Dm 644 -T {} "$(DESTDIR)$(DATA_DIR)/{}" \; )
-	install -Dm 755 -s $(BIN)/SDL/sameboy $(DESTDIR)$(PREFIX)/bin/sameboy
-	install -Dm 755 -s $(BIN)/XdgThumbnailer/sameboy-thumbnailer $(DESTDIR)$(PREFIX)/bin/sameboy-thumbnailer
-	install -Dm 644 XdgThumbnailer/sameboy.thumbnailer $(DESTDIR)$(PREFIX)/share/thumbnailers/sameboy.thumbnailer
+	install -Dm 755 -s $(BIN)/SDL/sameboy $(DESTDIR)$(bindir)/sameboy
+	install -Dm 755 -s $(BIN)/XdgThumbnailer/sameboy-thumbnailer $(DESTDIR)$(bindir)/sameboy-thumbnailer
+	install -Dm 644 XdgThumbnailer/sameboy.thumbnailer $(DESTDIR)$(datadir)/thumbnailers/sameboy.thumbnailer
+ifneq ($(LIBRARY),)
+	$(install_headers)
+	$(install_pkgconf_file)
+endif
+ifeq ($(LIBRARY), shared)
+	$(call install_lib,$(LIB_SHARED))
+else ifeq ($(LIBRARY), static)
+	$(call install_lib,$(LIB_STATIC))
+else ifneq ($(LIBRARY),)
+	$(call install_lib,$(LIB_SHARED))
+	$(call install_lib,$(LIB_STATIC))
+endif
+
 ifeq ($(DESTDIR),)
 	xdg-mime install --novendor FreeDesktop/sameboy.xml
 	xdg-desktop-menu install --novendor FreeDesktop/sameboy.desktop
@@ -738,12 +810,12 @@ ifeq ($(DESTDIR),)
 		xdg-icon-resource install --novendor --theme hicolor --size $$size --context mimetypes FreeDesktop/ColorCartridge/$${size}x$${size}.png x-gameboy-color-rom; \
 	done
 else
-	install -Dm 644 FreeDesktop/sameboy.xml $(DESTDIR)$(PREFIX)/share/mime/sameboy.xml
-	install -Dm 644 FreeDesktop/sameboy.desktop $(DESTDIR)$(PREFIX)/share/applications/sameboy.desktop
+	install -Dm 644 FreeDesktop/sameboy.xml $(DESTDIR)$(datadir)/mime/sameboy.xml
+	install -Dm 644 FreeDesktop/sameboy.desktop $(DESTDIR)$(datadir)/applications/sameboy.desktop
 	for size in 16x16 32x32 64x64 128x128 256x256 512x512; do \
-		install -Dm 644 FreeDesktop/AppIcon/$$size.png $(DESTDIR)$(PREFIX)/share/icons/hicolor/$$size/apps/sameboy.png; \
-		install -Dm 644 FreeDesktop/Cartridge/$$size.png $(DESTDIR)$(PREFIX)/share/icons/hicolor/$$size/mimetypes/x-gameboy-rom.png; \
-		install -Dm 644 FreeDesktop/ColorCartridge/$$size.png $(DESTDIR)$(PREFIX)/share/icons/hicolor/$$size/mimetypes/x-gameboy-color-rom.png; \
+		install -Dm 644 FreeDesktop/AppIcon/$$size.png $(DESTDIR)$(datadir)/icons/hicolor/$$size/apps/sameboy.png; \
+		install -Dm 644 FreeDesktop/Cartridge/$$size.png $(DESTDIR)$(datadir)/icons/hicolor/$$size/mimetypes/x-gameboy-rom.png; \
+		install -Dm 644 FreeDesktop/ColorCartridge/$$size.png $(DESTDIR)$(datadir)/icons/hicolor/$$size/mimetypes/x-gameboy-color-rom.png; \
 	done
 endif
 endif
@@ -796,7 +868,23 @@ $(LIBDIR)/libsameboy.a: $(LIBDIR)/libsameboy.o
 	-@$(MKDIR) -p $(dir $@)
 	-@rm -f $@
 	ar -crs $@ $^
-
+
+$(LIBDIR)/libsameboy.so: $(LIBDIR)/libsameboy.o
+	-@$(MKDIR) -p $(dir $@)
+	-@rm -f $@
+	$(CC) -shared -o $@ $^
+
+$(PKGCONF_FILE): sameboy.pc.in
+	-@$(MKDIR) -p $(dir $@)
+	-@rm -f $@
+	sed -e 's,@prefix@,$(prefix),' \
+	 -e 's/@version@/$(VERSION)/' \
+	 -e 's,@exec_prefix@,$(PKGCONF_EXEC_PREFIX),' \
+	 -e 's,@includedir@,$(PKGCONF_INCLUDEDIR),' \
+	 -e 's,@libdir@,$(PKGCONF_LIBDIR),' $< > $@
+
+pkgconf: $(PKGCONF_FILE)
+
 $(INC)/%.h: Core/%.h
 	-@$(MKDIR) -p $(dir $@)
 	-@# CPPP doesn't like multibyte characters, so we replace the single quote character before processing so it doesn't complain
@@ -810,4 +898,4 @@ lib-unsupported:
 clean:
 	rm -rf build
 
-.PHONY: libretro tester cocoa ios _ios ios-ipa ios-deb liblib-unsupported bootroms
+.PHONY: libretro tester cocoa ios _ios ios-ipa ios-deb lib lib-unsupported bootroms pkgconf

README.md

@@ -53,12 +53,18 @@ On Windows, SameBoy also requires:
 To compile, simply run `make`. The targets are:
  * `cocoa` (Default for macOS)
  * `sdl` (Default for everything else)
- * `lib` (Creates libsameboy.o and libsameboy.a for statically linking SameBoy, as well as a headers directory with corresponding headers; currently not supported on Windows due to linker limitations)
+ * `lib` (Creates libsameboy.o, libsameboy.a and libsameboy.so for linking SameBoy, as well as a headers directory with corresponding headers; currently not supported on Windows due to linker limitations)
  * `ios` (Plain iOS .app bundle), `ios-ipa` (iOS IPA archive for side-loading), `ios-deb` (iOS deb package for jailbroken devices)
  * `libretro`
  * `bootroms`
  * `tester` 
 
+For convenience, when installing the static and shared libraries is
+desired, you can specify the LIBRARY=1 make variable to have the
+libraries built as part of the default target, as well as installed,
+along the headers. Alternatively, `LIBRARY=shared` will install just
+the shared library, while `LIBRARY=static` only the static one.
+
 You may also specify `CONF=debug` (default), `CONF=release`, `CONF=native_release` or `CONF=fat_release`  to control optimization, symbols and multi-architectures. `native_release` is faster than `release`, but is optimized to the host's CPU and therefore is not portable. `fat_release` is exclusive to macOS and builds x86-64 and ARM64 fat binaries; this requires using a recent enough `clang` and macOS SDK using `xcode-select`, or setting them explicitly with `CC=` and `SYSROOT=`, respectively. All other configurations will build to your host architecture, except for the iOS targets. You may set `BOOTROMS_DIR=...` to a directory containing precompiled boot ROM files, otherwise the build system will compile and use SameBoy's own boot ROMs.
 
 The SDL port will look for resource files with a path relative to executable and inside the directory specified by the `DATA_DIR` variable. If you are packaging SameBoy, you may wish to override this by setting the `DATA_DIR` variable during compilation to the target path of the directory containing all files (apart from the executable, that's not necessary) from the `build/bin/SDL` directory in the source tree. Make sure the variable ends with a `/` character. On FreeDesktop environments, `DATA_DIR` will default to `/usr/local/share/sameboy/`. `PREFIX` and `DESTDIR` follow their standard usage and default to an empty string an `/usr/local`, respectively

sameboy.pc.in

@@ -0,0 +1,10 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+includedir=@includedir@
+libdir=@libdir@
+
+Name: sameboy
+Description: The SameBoy library
+Version: @version@
+Cflags: -I${includedir}/sameboy
+Libs: -L${libdir} -lsameboy