build: support cross-compilation by natively building gtk-update-icon-cache

When cross-compiling, instead of depending on a natively built GTK+ (which means
building Glib, ATK, Pango, gdk-pixbuf, libX11...) for gtk-update-icon-cache,
find the host compiler and gdk-pixbuf, and build another gtk-update-icon-cache
with that.

This uses AX_PROG_CC_FOR_BUILD from autostars to find the host compiler, and
assumes that you'd set PKG_CONFIG_FOR_BUILD to a host pkg-config binary.

https://bugzilla.gnome.org/show_bug.cgi?id=691301

configure.ac

@@ -29,6 +29,9 @@ AC_CONFIG_SRCDIR([gdk/gdktypes.h])
 AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_AUX_DIR([build-aux])
 
+AC_CANONICAL_HOST
+AC_CANONICAL_TARGET
+
 # Define a string for the earliest version that this release has
 # backwards binary compatibility with for all interfaces a module
 # might. Unless we add module-only API with lower stability
@@ -123,6 +126,7 @@ AC_SUBST([GAIL_LT_CURRENT_MINUS_AGE],[gail_lt_current_minus_age])
 
 # Checks for programs.
 AC_PROG_CC
+AX_PROG_CC_FOR_BUILD
 AC_PROG_CC_C_O
 AC_PROG_MKDIR_P
 AC_PROG_INSTALL
@@ -134,8 +138,6 @@ AC_SUBST(GETTEXT_PACKAGE)
 AC_DEFINE_UNQUOTED(GETTEXT_PACKAGE, "$GETTEXT_PACKAGE",
                    [The prefix for our gettext translation domains.])
 
-AC_CANONICAL_HOST
-
 MATH_LIB=-lm
 AC_MSG_CHECKING([for native Win32])
 LIB_EXE_MACHINE_FLAG=X86
@@ -905,14 +907,32 @@ dnl Look for a host system's gdk-pixbuf-csource if we are cross-compiling
 
 AM_CONDITIONAL(CROSS_COMPILING, test $cross_compiling = yes)
 
-if test "x$cross_compiling" = xyes || test "x$enable_gtk2_dependency" = xyes; then
+AS_IF([test "x$enable_gtk2_dependency" = xyes],
-  AC_PATH_PROG(GTK_UPDATE_ICON_CACHE, gtk-update-icon-cache, no)
+      [AC_PATH_PROG(GTK_UPDATE_ICON_CACHE, gtk-update-icon-cache, no)
-  if test x$GTK_UPDATE_ICON_CACHE = xno; then
+       if test x$GTK_UPDATE_ICON_CACHE = xno; then
-    REBUILD_PNGS=#
+         REBUILD_PNGS=#
-  fi
+       fi],
-fi
 
-AM_CONDITIONAL(USE_EXTERNAL_ICON_CACHE, [test "x$cross_compiling" = xyes || test "x$enable_gtk2_dependency" = xyes])
+      [test "x$cross_compiling" = xyes],
+      [# If no GTK+2 dependency and cross compiling, we need to find a host gdk-pixbuf.
+       # pkg.m4 blocks all variable starting with PKG, so allow this one
+       m4_pattern_allow([PKG_CONFIG_FOR_BUILD])
+
+       AS_IF([test x$PKG_CONFIG_FOR_BUILD = x],
+             [AC_MSG_ERROR([You must define PKG_CONFIG_FOR_BUILD when cross compiling])])
+
+       AC_MSG_CHECKING([for native gdk-pixbuf])
+       AS_IF([AC_RUN_LOG([$PKG_CONFIG_FOR_BUILD --exists --print-errors gdk-pixbuf-2.0])],
+             [AC_MSG_RESULT([yes])],
+             [AC_MSG_ERROR([native gdk-pixbuf not found])])
+
+       NATIVE_GDKPIXBUF_CFLAGS=`$PKG_CONFIG_FOR_BUILD --cflags gdk-pixbuf-2.0`
+       NATIVE_GDKPIXBUF_LIBS=`$PKG_CONFIG_FOR_BUILD --libs gdk-pixbuf-2.0`
+       AC_SUBST(NATIVE_GDKPIXBUF_CFLAGS)
+       AC_SUBST(NATIVE_GDKPIXBUF_LIBS)]
+)
+
+AM_CONDITIONAL(USE_EXTERNAL_ICON_CACHE, [test "x$enable_gtk2_dependency" = xyes])
 
 AC_PATH_PROG(GDK_PIXBUF_CSOURCE, gdk-pixbuf-csource, no)
 
@@ -1787,6 +1807,7 @@ gtk/makefile.msc
 gtk/gtkversion.h
 gtk/gtk-win32.rc
 gtk/a11y/Makefile
+gtk/native/Makefile
 gtk/tests/Makefile
 libgail-util/Makefile
 modules/Makefile

gtk/Makefile.am

@@ -16,7 +16,7 @@ else
 GTK_PRINT_PREVIEW_COMMAND="evince --unlink-tempfile --preview --print-settings %s %f"
 endif
 
-SUBDIRS = a11y . tests
+SUBDIRS = a11y native . tests
 
 if HAVE_PAPI_CUPS
 GTK_PRINT_BACKENDS=file,papi,cups
@@ -1654,12 +1654,20 @@ stamp-icons: $(STOCK_ICONS)
 if USE_EXTERNAL_ICON_CACHE
 gtk_update_icon_cache_program = $(GTK_UPDATE_ICON_CACHE)
 else
+if CROSS_COMPILING
+gtk_update_icon_cache_program = ./native/native-update-icon-cache
+else
 gtk_update_icon_cache_program = ./gtk-update-icon-cache
 endif
+endif
 
 gtkbuiltincache.h: @REBUILD@ stamp-icons
 if !USE_EXTERNAL_ICON_CACHE
-	$(AM_V_at) $(MAKE) $(AM_MAKEFLAGS) gtk-update-icon-cache$(EXEEXT) $(GTK_UPDATE_ICON_CACHE_MANIFEST)
+if CROSS_COMPILING
+	$(AM_V_at) $(MAKE) $(AM_MAKEFLAGS) -C native/
+else
+	$(AM_V_at) $(MAKE) $(AM_MAKEFLAGS) gtk-update-icon-cache$(EXEEXT)
+endif
 endif
 	$(AM_V_GEN) $(gtk_update_icon_cache_program) --quiet --force --ignore-theme-index		\
 	   --source builtin_icons stock-icons > gtkbuiltincache.h.tmp &&        \

gtk/native/Makefile.am

@@ -0,0 +1,12 @@
+CC = @CC_FOR_BUILD@
+CFLAGS = @CFLAGS_FOR_BUILD@
+CPP = @CPP_FOR_BUILD@
+CPPFLAGS = @CPPFLAGS_FOR_BUILD@
+LDFLAGS = @LDFLAGS_FOR_BUILD@
+
+if CROSS_COMPILING
+noinst_PROGRAMS = native-update-icon-cache
+native_update_icon_cache_CFLAGS = $(NATIVE_GDKPIXBUF_CFLAGS)
+native_update_icon_cache_LDADD = $(NATIVE_GDKPIXBUF_LIBS)
+native_update_icon_cache_SOURCES = $(srcdir)/../updateiconcache.c
+endif

m4/ax_prog_cc_for_build.m4

@@ -0,0 +1,125 @@
+# ===========================================================================
+#   http://www.gnu.org/software/autoconf-archive/ax_prog_cc_for_build.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_PROG_CC_FOR_BUILD
+#
+# DESCRIPTION
+#
+#   This macro searches for a C compiler that generates native executables,
+#   that is a C compiler that surely is not a cross-compiler. This can be
+#   useful if you have to generate source code at compile-time like for
+#   example GCC does.
+#
+#   The macro sets the CC_FOR_BUILD and CPP_FOR_BUILD macros to anything
+#   needed to compile or link (CC_FOR_BUILD) and preprocess (CPP_FOR_BUILD).
+#   The value of these variables can be overridden by the user by specifying
+#   a compiler with an environment variable (like you do for standard CC).
+#
+#   It also sets BUILD_EXEEXT and BUILD_OBJEXT to the executable and object
+#   file extensions for the build platform, and GCC_FOR_BUILD to `yes' if
+#   the compiler we found is GCC. All these variables but GCC_FOR_BUILD are
+#   substituted in the Makefile.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Paolo Bonzini <bonzini@gnu.org>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 7
+
+AU_ALIAS([AC_PROG_CC_FOR_BUILD], [AX_PROG_CC_FOR_BUILD])
+AC_DEFUN([AX_PROG_CC_FOR_BUILD], [dnl
+AC_REQUIRE([AC_PROG_CC])dnl
+AC_REQUIRE([AC_PROG_CPP])dnl
+AC_REQUIRE([AC_EXEEXT])dnl
+AC_REQUIRE([AC_CANONICAL_SYSTEM])dnl
+
+dnl Use the standard macros, but make them use other variable names
+dnl
+pushdef([ac_cv_prog_CPP], ac_cv_build_prog_CPP)dnl
+pushdef([ac_cv_prog_gcc], ac_cv_build_prog_gcc)dnl
+pushdef([ac_cv_prog_cc_works], ac_cv_build_prog_cc_works)dnl
+pushdef([ac_cv_prog_cc_cross], ac_cv_build_prog_cc_cross)dnl
+pushdef([ac_cv_prog_cc_g], ac_cv_build_prog_cc_g)dnl
+pushdef([ac_cv_exeext], ac_cv_build_exeext)dnl
+pushdef([ac_cv_objext], ac_cv_build_objext)dnl
+pushdef([ac_exeext], ac_build_exeext)dnl
+pushdef([ac_objext], ac_build_objext)dnl
+pushdef([CC], CC_FOR_BUILD)dnl
+pushdef([CPP], CPP_FOR_BUILD)dnl
+pushdef([CFLAGS], CFLAGS_FOR_BUILD)dnl
+pushdef([CPPFLAGS], CPPFLAGS_FOR_BUILD)dnl
+pushdef([LDFLAGS], LDFLAGS_FOR_BUILD)dnl
+pushdef([host], build)dnl
+pushdef([host_alias], build_alias)dnl
+pushdef([host_cpu], build_cpu)dnl
+pushdef([host_vendor], build_vendor)dnl
+pushdef([host_os], build_os)dnl
+pushdef([ac_cv_host], ac_cv_build)dnl
+pushdef([ac_cv_host_alias], ac_cv_build_alias)dnl
+pushdef([ac_cv_host_cpu], ac_cv_build_cpu)dnl
+pushdef([ac_cv_host_vendor], ac_cv_build_vendor)dnl
+pushdef([ac_cv_host_os], ac_cv_build_os)dnl
+pushdef([ac_cpp], ac_build_cpp)dnl
+pushdef([ac_compile], ac_build_compile)dnl
+pushdef([ac_link], ac_build_link)dnl
+
+save_cross_compiling=$cross_compiling
+save_ac_tool_prefix=$ac_tool_prefix
+cross_compiling=no
+ac_tool_prefix=
+
+AC_PROG_CC
+AC_PROG_CPP
+AC_EXEEXT
+
+ac_tool_prefix=$save_ac_tool_prefix
+cross_compiling=$save_cross_compiling
+
+dnl Restore the old definitions
+dnl
+popdef([ac_link])dnl
+popdef([ac_compile])dnl
+popdef([ac_cpp])dnl
+popdef([ac_cv_host_os])dnl
+popdef([ac_cv_host_vendor])dnl
+popdef([ac_cv_host_cpu])dnl
+popdef([ac_cv_host_alias])dnl
+popdef([ac_cv_host])dnl
+popdef([host_os])dnl
+popdef([host_vendor])dnl
+popdef([host_cpu])dnl
+popdef([host_alias])dnl
+popdef([host])dnl
+popdef([LDFLAGS])dnl
+popdef([CPPFLAGS])dnl
+popdef([CFLAGS])dnl
+popdef([CPP])dnl
+popdef([CC])dnl
+popdef([ac_objext])dnl
+popdef([ac_exeext])dnl
+popdef([ac_cv_objext])dnl
+popdef([ac_cv_exeext])dnl
+popdef([ac_cv_prog_cc_g])dnl
+popdef([ac_cv_prog_cc_cross])dnl
+popdef([ac_cv_prog_cc_works])dnl
+popdef([ac_cv_prog_gcc])dnl
+popdef([ac_cv_prog_CPP])dnl
+
+dnl Finally, set Makefile variables
+dnl
+BUILD_EXEEXT=$ac_build_exeext
+BUILD_OBJEXT=$ac_build_objext
+AC_SUBST(BUILD_EXEEXT)dnl
+AC_SUBST(BUILD_OBJEXT)dnl
+AC_SUBST([CFLAGS_FOR_BUILD])dnl
+AC_SUBST([CPPFLAGS_FOR_BUILD])dnl
+AC_SUBST([LDFLAGS_FOR_BUILD])dnl
+])