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[Qemu-devel] [PULL 05/21] use _Static_assert in QEMU_BUILD_BUG_ON
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 05/21] use _Static_assert in QEMU_BUILD_BUG_ON |
Date: |
Fri, 5 May 2017 12:13:21 +0200 |
From: Andreas Grapentin <address@hidden>
QEMU_BUILD_BUG_ON should use C11's _Static_assert, if the compiler supports it,
to provide more readable messages on failure.
We check for _Static_assert in configure, and set CONFIG_STATIC_ASSERT
accordingly. QEMU_BUILD_BUG_ON invokes _Static_assert if CONFIG_STATIC_ASSERT
is defined, and reverts to the old way otherwise.
That way, systems without C11 conforming compiler will still have the old
messages, as verified by intentionally breaking the configure check.
the following example output was generated by inverting the condition in
QEMU_BUILD_BUG_ON:
without _Static_assert:
> In file included from /qemu/include/qemu/osdep.h:36:0,
> from /qemu/qga/commands.c:13:
> /qemu/qga/commands.c: In function ‘qmp_guest_exec_status’:
> /qemu/include/qemu/compiler.h:89:12: error: negative width in bit-field
> ‘<anonymous>’
> struct { \
> ^
> /qemu/include/qemu/compiler.h:96:38: note: in expansion of macro
> QEMU_BUILD_BUG_ON_STRUCT’
> #define QEMU_BUILD_BUG_ON(x) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
> ^~~~~~~~~~~~~~~~~~~~~~~~
> /qemu/include/qemu/atomic.h:146:5: note: in expansion of macro
> ‘QEMU_BUILD_BUG_ON’
> QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
> ^~~~~~~~~~~~~~~~~
> /qemu/include/qemu/atomic.h:417:5: note: in expansion of macro
> ‘atomic_load_acquire’
> atomic_load_acquire(ptr)
> ^~~~~~~~~~~~~~~~~~~
> /qemu/qga/commands.c:160:21: note: in expansion of macro ‘atomic_mb_read’
> bool finished = atomic_mb_read(&gei->finished);
> ^~~~~~~~~~~~~~
with _Static_assert:
> In file included from /qemu/include/qemu/osdep.h:36:0,
> from /qemu/qga/commands.c:13:
> /qemu/qga/commands.c: In function ‘qmp_guest_exec_status’:
> /qemu/include/qemu/compiler.h:94:30: error: static assertion failed: "not
> expecting: sizeof(*&gei->finished) > sizeof(void *)"
> #define QEMU_BUILD_BUG_ON(x) _Static_assert((x), #x)
> ^
> /qemu/include/qemu/atomic.h:146:5: note: in expansion of macro
> ‘QEMU_BUILD_BUG_ON’
> QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
> ^~~~~~~~~~~~~~~~~
> /qemu/include/qemu/atomic.h:417:5: note: in expansion of macro
> ‘atomic_load_acquire’
> atomic_load_acquire(ptr)
> ^~~~~~~~~~~~~~~~~~~
> /qemu/qga/commands.c:160:21: note: in expansion of macro ‘atomic_mb_read’
> bool finished = atomic_mb_read(&gei->finished);
> ^~~~~~~~~~~~~~
Signed-off-by: Andreas Grapentin <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
configure | 18 ++++++++++++++++++
include/qemu/compiler.h | 4 +++-
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/configure b/configure
index ff2c81f2c7..7c020c076b 100755
--- a/configure
+++ b/configure
@@ -4853,6 +4853,20 @@ EOF
fi
##########################################
+# check for _Static_assert()
+
+have_static_assert=no
+cat > $TMPC << EOF
+_Static_assert(1, "success");
+int main(void) {
+ return 0;
+}
+EOF
+if compile_prog "" "" ; then
+ have_static_assert=yes
+fi
+
+##########################################
# End of CC checks
# After here, no more $cc or $ld runs
@@ -5848,6 +5862,10 @@ if test "$have_sysmacros" = "yes" ; then
echo "CONFIG_SYSMACROS=y" >> $config_host_mak
fi
+if test "$have_static_assert" = "yes" ; then
+ echo "CONFIG_STATIC_ASSERT=y" >> $config_host_mak
+fi
+
# Hold two types of flag:
# CONFIG_THREAD_SETNAME_BYTHREAD - we've got a way of setting the name on
# a thread we have a handle to
diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 18e610083a..340e5fdc09 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -82,7 +82,9 @@
int:(x) ? -1 : 1; \
}
-#ifdef __COUNTER__
+#if defined(CONFIG_STATIC_ASSERT)
+#define QEMU_BUILD_BUG_ON(x) _Static_assert(!(x), "not expecting: " #x)
+#elif defined(__COUNTER__)
#define QEMU_BUILD_BUG_ON(x) typedef QEMU_BUILD_BUG_ON_STRUCT(x) \
glue(qemu_build_bug_on__, __COUNTER__) __attribute__((unused))
#else
--
2.12.2
- [Qemu-devel] [PULL 00/21] Misc patches for 2017-05-05, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 02/21] hw/i386: Build-time assertion on pc/q35 reset register being identical., Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 03/21] char: Fix removing wrong GSource that be found by fd_in_tag, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 05/21] use _Static_assert in QEMU_BUILD_BUG_ON,
Paolo Bonzini <=
- [Qemu-devel] [PULL 01/21] hw/i386: Use Rev3 FADT (ACPI 2.0) instead of Rev1 to improve guest OS support., Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 04/21] target/i386: Add GDB XML register description support, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 06/21] vl: deprecate the "-hdachs" option, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 07/21] scsi: avoid an off-by-one error in megasas_mmio_write, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 10/21] trace: add qemu mutex lock and unlock trace events, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 11/21] checkpatch: Disallow glib asserts in main code, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 13/21] dump: Acquire BQL around vm_start() in dump thread, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 08/21] sgabios: update for "fix wrong video attrs for int 10h, ah==13h", Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 12/21] hax: Fix memory mapping de-duplication logic, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 09/21] vmw_pvscsi: check message ring page count at initialisation, Paolo Bonzini, 2017/05/05