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unicorn/qemu
Eric Blake 97c801d6a1
qapi: Prefer typesafe upcasts to qapi base classes
A previous patch (commit 1e6c1616) made it possible to
directly cast from a qapi flat union type to its base type.
However, it requires the use of a C cast, which turns off
compiler type-safety checks. Fortunately, no such casts
exist, just yet.

Regardless, add inline type-safe wrappers named
qapi_FOO_base() for any union type FOO that has a base,
which can be used for a safer upcast, and enhance the
testsuite to cover the new functionality.

A future patch will extend the upcast support to structs,
where such conversions do exist already.

Note that C makes const-correct upcasts annoying because
it lacks overloads; these functions cast away const so that
they can accept user pointers whether const or not, and the
result in turn can be assigned to normal or const pointers.
Alternatively, this could have been done with macros, but
type-safe macros are hairy, and not worthwhile here.

This patch just adds upcasts. None of our code needed to
downcast from a base qapi class to a child. Also, in the
case of grandchildren (such as BlockdevOptionsQcow2), the
caller will need to call two functions to get to the inner
base (although it wouldn't be too hard to generate a
qapi_FOO_base_base() if desired). If a user changes qapi
to alter the base class hierarchy, such as going from
'A -> C' to 'A -> B -> C', it will change the type of
'qapi_C_base()', and the compiler will point out the places
that are affected by the new base.

One alternative was proposed, but was deemed too ugly to use
in practice: the generators could output redundant
information using anonymous types:
| struct Child {
| union {
| struct {
| Type1 parent_member1;
| Type2 parent_member2;
| };
| Parent base;
| };
| };
With that ugly proposal, for a given qapi type, obj->member
and obj->base.member would refer to the same storage; allowing
convenience in working with members without needing 'base.'
allowing typesafe upcast without needing a C cast by accessing
'&obj->base', and allowing downcasts from the parent back to
the child possible through container_of(obj, Child, base).

Backports commit 30594fe1cd4355626e73b80645428105d0df3cf6 from qemu
2018-02-19 19:14:03 -05:00
..
crypto crypto: Clean up includes 2018-02-19 00:47:40 -05:00
default-configs arm64eb: add support for ARM64 big endian. 2017-04-24 23:30:01 +08:00
docs docs: clarify memory region lifecycle 2018-02-12 15:11:21 -05:00
fpu all: Clean up includes 2018-02-19 01:34:28 -05:00
hw x86: Clean up includes 2018-02-19 01:00:09 -05:00
include qapi: Introduce a first class 'any' type 2018-02-19 17:46:58 -05:00
qapi qapi: Introduce a first class 'any' type 2018-02-19 17:46:58 -05:00
qobject qobject: Clean up includes 2018-02-19 01:30:42 -05:00
qom qapi: Consistent generated code: prefer visitor 'v' 2018-02-19 18:21:53 -05:00
scripts qapi: Prefer typesafe upcasts to qapi base classes 2018-02-19 19:14:03 -05:00
target-arm tcg: Remove lingering references to gen_opc_buf 2018-02-19 01:42:55 -05:00
target-i386 tcg: Remove lingering references to gen_opc_buf 2018-02-19 01:42:55 -05:00
target-m68k m68k: Clean up includes 2018-02-19 01:06:05 -05:00
target-mips mips: Clean up includes 2018-02-19 00:45:08 -05:00
target-sparc sparc: Clean up includes 2018-02-19 00:52:41 -05:00
tcg tcg: Introduce temp_load 2018-02-19 11:44:01 -05:00
util util: Clean up includes 2018-02-19 01:27:55 -05:00
aarch64.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
aarch64eb.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
accel.c all: Clean up includes 2018-02-19 01:34:28 -05:00
arm.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
armeb.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
CODING_STYLE import 2015-08-21 15:04:50 +08:00
configure tcg: Drop ia64 host support 2018-02-04 18:33:02 -05:00
COPYING import 2015-08-21 15:04:50 +08:00
COPYING.LIB import 2015-08-21 15:04:50 +08:00
cpu-exec-common.c exec: Clean up includes 2018-02-19 00:49:55 -05:00
cpu-exec.c exec: Clean up includes 2018-02-19 00:49:55 -05:00
cpus.c exec: Clean up includes 2018-02-19 00:49:55 -05:00
cputlb.c exec: Clean up includes 2018-02-19 00:49:55 -05:00
exec.c exec: Clean up includes 2018-02-19 00:49:55 -05:00
gen_all_header.sh arm64eb: add support for ARM64 big endian. 2017-04-24 23:30:01 +08:00
glib_compat.c crypto: introduce new module for computing hash digests 2018-02-17 15:23:17 -05:00
HACKING import 2015-08-21 15:04:50 +08:00
header_gen.py target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
ioport.c all: Clean up includes 2018-02-19 01:34:28 -05:00
LICENSE import 2015-08-21 15:04:50 +08:00
m68k.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
Makefile qapi: Turn generators' mandatory option -i into an argument 2018-02-19 15:22:27 -05:00
Makefile.objs crypto: move crypto objects out of libqemuutil.la 2018-02-17 15:23:50 -05:00
Makefile.target tcg: split tcg_op_defs to -common 2018-02-17 15:23:51 -05:00
memory.c memory: Silence unused variable warning 2018-02-18 17:52:03 -05:00
memory_mapping.c all: Clean up includes 2018-02-19 01:34:28 -05:00
mips.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
mips64.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
mips64el.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
mipsel.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
powerpc.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
qapi-schema.json qapi: Lazy creation of array types 2018-02-19 18:55:35 -05:00
qemu-log.c all: Clean up includes 2018-02-19 01:34:28 -05:00
qemu-timer.c all: Clean up includes 2018-02-19 01:34:28 -05:00
rules.mak import 2015-08-21 15:04:50 +08:00
softmmu_template.h exec.c: Pass MemTxAttrs to iotlb_to_region so it uses the right AS 2018-02-17 23:19:00 -05:00
sparc.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
sparc64.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00
tcg-runtime.c all: Clean up includes 2018-02-19 01:34:28 -05:00
translate-all.c all: Clean up includes 2018-02-19 01:34:28 -05:00
translate-all.h translate-all: remove unnecessary argument to tb_invalidate_phys_range 2018-02-13 09:04:51 -05:00
translate-common.c exec: Clean up includes 2018-02-19 00:49:55 -05:00
unicorn_common.h qom/cpu: Add MemoryRegion property 2018-02-18 21:54:50 -05:00
VERSION import 2015-08-21 15:04:50 +08:00
vl.c vl.c: Remove periods and exclamation points from error messages 2018-02-17 15:24:14 -05:00
vl.h import 2015-08-21 15:04:50 +08:00
x86_64.h target-arm: Implement cpu_get_phys_page_attrs_debug 2018-02-18 22:15:50 -05:00