gcc: use toolchain wrapper

We have a toolchain wrapper for external toolchain, but it is also
beneficial for internal toolchains, for the following reasons:

1. It can make sure that BR2_TARGET_OPTIMIZATION is passed to the
   compiler even if a package's build system doesn't honor CFLAGS.
2. It allows us to do the unsafe path check (i.e. -I/usr/include)
   without patching gcc.
3. It makes it simpler to implement building each package with a
   separate staging directory (per-package staging).
4. It makes it simpler to implement a compiler hash check for ccache.

The wrapper is reused from the external toolchain. A third CROSS_PATH_
option is added to the wrapper: in this case, the real executable is in
the same directory, with the extension .real.

The creation of the simple symlinks is merged with the creation of the
wrapper symlinks, otherwise part of the -gcc-ar handling logic would
have to be repeated.

The complex case-condition could be refactored with the one for the
external toolchain, but then it becomes even more complex because
they each have special corner cases. For example, the internal
toolchain has to handle *.real to avoid creating an extra indirection
after host-gcc-{final,initial}-rebuild.

Instead of creating the .real files, it would also have been possible
to install the internal toolchain in $(HOST_DIR)/opt, similar to what
we do for the external toolchain. However, then we would also have to
copy things to the sysroot and do more of the magic that the external
toolchain is doing. So keeping it in $(HOST_DIR)/usr/bin is much
simpler.

Note that gcc-initial has to be wrapped as well, because it is used for
building libc and we want to apply the same magic when building libc.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Fabio Porcedda <fabio.porcedda@gmail.com>
Cc: Jérôme Oufella <jerome.oufella@savoirfairelinux.com>
Reviewed-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/gcc/gcc-final/gcc-final.mk

@@ -96,14 +96,11 @@ endef
 
 HOST_GCC_FINAL_POST_INSTALL_HOOKS += HOST_GCC_FINAL_CREATE_CC_SYMLINKS
 
-# Create <arch>-linux-<tool> symlinks
-define HOST_GCC_FINAL_CREATE_SIMPLE_SYMLINKS
-	(cd $(HOST_DIR)/usr/bin; for i in $(GNU_TARGET_NAME)-*; do \
-		ln -snf $$i $(ARCH)-linux$${i##$(GNU_TARGET_NAME)}; \
-	done)
-endef
-
-HOST_GCC_FINAL_POST_INSTALL_HOOKS += HOST_GCC_FINAL_CREATE_SIMPLE_SYMLINKS
+HOST_GCC_FINAL_TOOLCHAIN_WRAPPER_ARGS += $(HOST_GCC_COMMON_TOOLCHAIN_WRAPPER_ARGS)
+HOST_GCC_FINAL_POST_BUILD_HOOKS += TOOLCHAIN_BUILD_WRAPPER
+# Note: this must be done after CREATE_CC_SYMLINKS, otherwise the
+# -cc symlink to the wrapper is not created.
+HOST_GCC_FINAL_POST_INSTALL_HOOKS += HOST_GCC_INSTALL_WRAPPER_AND_SIMPLE_SYMLINKS
 
 # In gcc 4.7.x, the ARM EABIhf library loader path for (e)glibc was not
 # correct, so we create a symbolic link to make things work

package/gcc/gcc-initial/gcc-initial.mk

@@ -62,4 +62,8 @@ HOST_GCC_INITIAL_MAKE_OPTS += all-target-libgcc
 HOST_GCC_INITIAL_INSTALL_OPTS += install-target-libgcc
 endif
 
+HOST_GCC_INITIAL_TOOLCHAIN_WRAPPER_ARGS += $(HOST_GCC_COMMON_TOOLCHAIN_WRAPPER_ARGS)
+HOST_GCC_INITIAL_POST_BUILD_HOOKS += TOOLCHAIN_BUILD_WRAPPER
+HOST_GCC_INITIAL_POST_INSTALL_HOOKS += HOST_GCC_INSTALL_WRAPPER_AND_SIMPLE_SYMLINKS
+
 $(eval $(host-autotools-package))

package/gcc/gcc.mk

@@ -235,4 +235,38 @@ HOST_GCC_COMMON_CONF_OPTS += \
 	--with-long-double-128
 endif
 
+HOST_GCC_COMMON_TOOLCHAIN_WRAPPER_ARGS += -DBR_CROSS_PATH_SUFFIX='".real"'
+
+# The LTO support in gcc creates wrappers for ar, ranlib and nm which load
+# the lto plugin. These wrappers are called *-gcc-ar, *-gcc-ranlib, and
+# *-gcc-nm and should be used instead of the real programs when -flto is
+# used. However, we should not add the toolchain wrapper for them, and they
+# match the *cc-* pattern. Therefore, an additional case is added for *-ar,
+# *-ranlib and *-nm.
+# Avoid that a .real is symlinked a second time.
+# Also create <arch>-linux-<tool> symlinks.
+define HOST_GCC_INSTALL_WRAPPER_AND_SIMPLE_SYMLINKS
+	$(Q)cd $(HOST_DIR)/usr/bin; \
+	for i in $(GNU_TARGET_NAME)-*; do \
+		case "$$i" in \
+		*.real) \
+			;; \
+		*-ar|*-ranlib|*-nm) \
+			ln -snf $$i $(ARCH)-linux$${i##$(GNU_TARGET_NAME)}; \
+			;; \
+		*cc|*cc-*|*++|*++-*|*cpp) \
+			rm -f $$i.real; \
+			mv $$i $$i.real; \
+			ln -sf toolchain-wrapper $$i; \
+			ln -sf toolchain-wrapper $(ARCH)-linux$${i##$(GNU_TARGET_NAME)}; \
+			ln -snf $$i.real $(ARCH)-linux$${i##$(GNU_TARGET_NAME)}.real; \
+			;; \
+		*) \
+			ln -snf $$i $(ARCH)-linux$${i##$(GNU_TARGET_NAME)}; \
+			;; \
+		esac; \
+	done
+
+endef
+
 include $(sort $(wildcard package/gcc/*/*.mk))

toolchain/toolchain-wrapper.c

@@ -138,8 +138,10 @@ int main(int argc, char **argv)
 	/* Fill in the relative paths */
 #ifdef BR_CROSS_PATH_REL
 	ret = snprintf(path, sizeof(path), "%s/" BR_CROSS_PATH_REL "/%s", absbasedir, basename);
-#else /* BR_CROSS_PATH_ABS */
+#elif BR_CROSS_PATH_ABS
 	ret = snprintf(path, sizeof(path), BR_CROSS_PATH_ABS "/%s", basename);
+#else /* BR_CROSS_PATH_SUFFIX */
+	ret = snprintf(path, sizeof(path), "%s/usr/bin/%s" BR_CROSS_PATH_SUFFIX, absbasedir, basename);
 #endif
 	if (ret >= sizeof(path)) {
 		perror(__FILE__ ": overflow");