emulators/virtualbox-ose: Switch build to USES= compiler:c++14-lang

The runtime breakage that started occurring after the LLVM 7 -> 8 transition
has been diagnosed with help from cem@, and the attached patch fixes it. The
problem ended up being that tail-call optimization was being applied to this
function (which should probably be written in assembly instead) and moving
the tail-call to later on after some stack manipulations. The problem with
this is that this particular function uses alloca() to carefully craft a
stack that it's expecting to be used for the function it's calling at the
end.

The new patch fixes this using a technique that was committed later on in
upstream changeset 75061 to address a similar failure with GCC sanitizers
enabled. The FreeBSD-specific component of this patch is using the different
stack setup if __clang__ is defined as well.

The extra hunk in the Config patch has been added because the VirtualBox
build system cannot cope with LLVM version numbers in the way it's
expecting. Hardcode it to GCC 4.2 for FreeBSD, which is what the clang
__GNU* macros describe, to fix build breakage that happens with newer LLVM
as the build system decides our LLVM is an even older and more broken
version of GCC with a broken regparm.

PR:		236616, 244847
Approved by:	koobs (mentor)
MFH:		2020Q2 (blanket: major runtime build fix)

emulators/virtualbox-ose/Makefile

@@ -3,7 +3,7 @@
 
 PORTNAME=	virtualbox-ose
 PORTVERSION=	5.2.34
-PORTREVISION=	2
+PORTREVISION=	3
 CATEGORIES=	emulators
 MASTER_SITES=	https://download.oracle.com/virtualbox/${PORTVERSION}/
 DISTFILES=	VirtualBox-${PORTVERSION}${EXTRACT_SUFX} ${GUESTADDITIONS}
@@ -30,13 +30,8 @@ CPE_PRODUCT=	vm_virtualbox
 
 WRKSRC=		${WRKDIR}/VirtualBox-${PORTVERSION}
 ONLY_FOR_ARCHS=	i386 amd64
-USES=		cpe gnome iconv pkgconfig ssl tar:bzip2
+USES=		compiler:c++14-lang cpe gnome iconv pkgconfig ssl tar:bzip2
 USE_GNOME=	libidl libxml2
-# machine/atomic.h may use features that are only available in GCC9.  This is
-# a workaround, anyways- we should be expressing USES= compiler:c++14-lang, but
-# contemporary clang miscompiles virtualbox in some fashion and yields runtime
-# breakage.
-USE_GCC=	any
 
 HAS_CONFIGURE=	yes
 CONFIGURE_ARGS=	--disable-java --passive-mesa

emulators/virtualbox-ose/files/patch-Config.kmk

@@ -74,6 +74,17 @@
   # branding
   VBOX_BRAND_LICENSE_HTML             := $(PATH_ROOT)/doc/License-gpl-2.0.html
   VBOX_BRAND_LICENSE_RTF              := $(PATH_ROOT)/doc/License-gpl-2.0.rtf
+@@ -2538,6 +2534,10 @@ ifeq ($(KBUILD_HOST),win) ## @todo can drop this now, 
+  # This isn't important (yet) on windows, so cook the result until
+  # cygwin is feeling better.
+  VBOX_GCC_VERSION := $(int-add $(int-mul 10000, 3), $(int-mul 100, 3), 3)
++else ifeq($(KBUILD_HOST,freebsd))
++ # At a minimum, we'll be building with GCC 4.2 on FreeBSD. LLVM will always
++ # pose as GCC 4.2 anyways, so this seems safe.
++ VBOX_GCC_VERSION := $(int-add $(int-mul 10000, 4), $(int-mul 100, 2), 0)
+ else
+  # This is kind of bad, the returned string needs to be re-evaluated before use.
+  # The reason for this hack is that the windows kmk_ash cannot deal with $((1+1)).
 @@ -4158,6 +4154,7 @@ ifdef VBOX_WITH_RAW_MODE
   TEMPLATE_VBoxRc_TOOL                = $(VBOX_GCC32_TOOL)
   TEMPLATE_VBoxRc_CXXFLAGS            = -fno-pie -nostdinc -g $(VBOX_GCC_pipe) $(VBOX_GCC_WERR) $(VBOX_GCC_PEDANTIC_CXX) $(VBOX_GCC32_Wno-variadic-macros) -fno-exceptions $(VBOX_GCC_GC_OPT) $(VBOX_GCC_GC_FP) -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -fno-strict-aliasing $(VBOX_GCC_fno-stack-protector) $(VBOX_GCC_fvisibility-hidden) $(VBOX_GCC_fvisibility-inlines-hidden) -fno-rtti $(VBOX_GCC_IPRT_FMT_CHECK)

emulators/virtualbox-ose/files/patch-src_libs_xpcom18a4_xpcom_reflect_xptcall_src_md_unix_xptcinvoke__x86__64__linux.cpp

@@ -0,0 +1,38 @@
+--- src/libs/xpcom18a4/xpcom/reflect/xptcall/src/md/unix/xptcinvoke_x86_64_linux.cpp.orig	2019-10-10 18:15:53 UTC
++++ src/libs/xpcom18a4/xpcom/reflect/xptcall/src/md/unix/xptcinvoke_x86_64_linux.cpp
+@@ -143,11 +143,22 @@ XPTC_InvokeByIndex(nsISupports * that, PRUint32 method
+     if (nr_stack)
+         nr_stack = (nr_stack + 1) & ~1;
+ 
++#if !defined(VBOX_WITH_GCC_SANITIZER) && !defined(__clang__)
+     // Load parameters to stack, if necessary
+     PRUint64 *stack = (PRUint64 *) __builtin_alloca(nr_stack * 8);
++#else
++    typedef struct { PRUint64 stack[20]; } methodStack;
++    if (nr_stack > 20)
++        return NS_ERROR_CALL_FAILED;
++    methodStack stack;
++#endif
+     PRUint64 gpregs[GPR_COUNT];
+     double fpregs[FPR_COUNT];
++#if !defined(VBOX_WITH_GCC_SANITIZER) && !defined(__clang__)
+     invoke_copy_to_stack(stack, paramCount, params, gpregs, fpregs);
++#else
++    invoke_copy_to_stack(stack.stack, paramCount, params, gpregs, fpregs);
++#endif
+ 
+     // Load FPR registers from fpregs[]
+     register double d0 asm("xmm0");
+@@ -205,7 +216,12 @@ XPTC_InvokeByIndex(nsISupports * that, PRUint32 method
+     methodAddress += 8 * methodIndex;
+     methodAddress = *((PRUint64 *)methodAddress);
+     
++#if !defined(VBOX_WITH_GCC_SANITIZER) && !defined(__clang__)
+     typedef PRUint32 (*Method)(PRUint64, PRUint64, PRUint64, PRUint64, PRUint64, PRUint64);
+     PRUint32 result = ((Method)methodAddress)(a0, a1, a2, a3, a4, a5);
++#else
++    typedef PRUint32 (*Method)(PRUint64, PRUint64, PRUint64, PRUint64, PRUint64, PRUint64, methodStack);
++    PRUint32 result = ((Method)methodAddress)(a0, a1, a2, a3, a4, a5, stack);
++#endif
+     return result;
+ }