toolchain: add variadic MI thunk support flag

GCC uses thunk functions to adjust the 'this' pointer when calling C++
member functions in classes derived with multiple inheritance.
Generation of thunk functions requires support from the compiler back
end. In the absence of that support target-independent code in the C++
front end is used to generate thunk functions, but it does not support
vararg functions.

Support for this feature is currently missing in or1k and xtensa
toolchains.

Add hidden option BR2_TOOLCHAIN_SUPPORTS_VARIADIC_MI_THUNK that
indicates presence of this feature in the toolchain. Add dependency to
packages that require this feature to be built.

Fixes:
http://autobuild.buildroot.net/results/c9e660c764edbd7cf0ae54ab0f0f412464721446/
http://autobuild.buildroot.net/results/9a3bf4b411c418ea78d59e35d23ba865dd453890/

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

diff --git a/package/libtorrent-rasterbar/Config.in b/package/libtorrent-rasterbar/Config.in
index aa986f2388e09a8da3294a0651e39c17daf4ded9..6c55085947f2f4dfee13c2397d27f588802d920b 100644 (file)
--- a/package/libtorrent-rasterbar/Config.in
+++ b/package/libtorrent-rasterbar/Config.in
@@ -1,4 +1,5 @@
 comment "libtorrent-rasterbar needs a toolchain w/ C++, threads, wchar, gcc >= 4.8"
+       depends on BR2_TOOLCHAIN_SUPPORTS_VARIADIC_MI_THUNK
        depends on !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_HAS_THREADS || !BR2_USE_WCHAR || \
                !BR2_HOST_GCC_AT_LEAST_4_8 || !BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
 
@@ -8,6 +9,7 @@ config BR2_PACKAGE_LIBTORRENT_RASTERBAR
        depends on BR2_HOST_GCC_AT_LEAST_4_8
        depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_8
        depends on BR2_TOOLCHAIN_HAS_THREADS # boost
+       depends on BR2_TOOLCHAIN_SUPPORTS_VARIADIC_MI_THUNK
        depends on BR2_USE_WCHAR # boost
        select BR2_PACKAGE_BOOST
        select BR2_PACKAGE_BOOST_CHRONO

diff --git a/toolchain/Config.in b/toolchain/Config.in
index 275f9f9cddd4fb3ead1fab9be8da41dd0bbc1812..bcbc3cf98432ae40706850debbb1ad2f7100ecb7 100644 (file)
--- a/toolchain/Config.in
+++ b/toolchain/Config.in
@@ -100,6 +100,19 @@ config BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS
        depends on !BR2_sparc_v8
        depends on !BR2_m68k_cf5208
 
+# GCC uses thunk functions to adjust the 'this' pointer when calling
+# C++ member functions in classes derived with multiple inheritance.
+# Generation of thunk functions requires support from the compiler
+# back end. In the absence of that support target-independent code
+# in the C++ front end is used to generate thunk functions, but it
+# does not support vararg functions.
+# or1k will support it in the gcc mainline starting with gcc-9.
+config BR2_TOOLCHAIN_SUPPORTS_VARIADIC_MI_THUNK
+       bool
+       default y
+       depends on !BR2_or1k
+       depends on !BR2_xtensa
+
 # Prior to gcc 7.x, exception_ptr, nested_exception and future from
 # libstdc++ would only be provided on architectures that support
 # always lock-free atomic ints. See