On 2026-08-21 13:33, Philippe Mathieu-Daudé wrote:
On 21/8/26 12:49, Philippe Mathieu-Daudé wrote:
From: Philippe Mathieu-Daudé <[email protected]>
Use _Generic() controlling-expression to add the const-qualified
variants of cpu_env(), env_cpu() and env_archcpu(). This allows to
safely access CPU architecture state when it should not be modified.
Alias env_cpu_const() which is still used.
Suggested-by: Richard Henderson <[email protected]>
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Marc-André Lureau <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
---
Following checkpatch.pl errors ignored:
ERROR: spaces required around that ':' (ctx:VxE)
#46: FILE: include/exec/cpu-common.h:89:
+ CPUArchState: \
^
ERROR: spaces required around that ':' (ctx:VxE)
#62: FILE: include/exec/cpu-common.h:101:
+ CPUArchState: \
^
ERROR: spaces required around that ':' (ctx:VxE)
#90: FILE: include/hw/core/cpu.h:605:
+ CPUState: \
^
total: 3 errors, 0 warnings, 64 lines checked
---
include/exec/cpu-common.h | 30 +++++++++++-------------------
include/hw/core/cpu.h | 17 ++++++++++++-----
2 files changed, 23 insertions(+), 24 deletions(-)
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 6594f7fa1be..bffef677607 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -85,21 +85,11 @@ static inline bool cpu_loop_exit_requested(const
CPUState *cpu)
*
* Return the ArchCPU associated with the environment.
*/
-static inline ArchCPU *env_archcpu(CPUArchState *env)
-{
- return (void *)env - sizeof(CPUState);
-}
-
-/**
- * env_cpu_const(env)
- * @env: The architecture environment
- *
- * Return the CPUState associated with the environment.
- */
-static inline const CPUState *env_cpu_const(const CPUArchState *env)
-{
- return (void *)env - sizeof(CPUState);
-}
+#define env_archcpu(env) _Generic(*(env), \
+ CPUArchState: \
+ (ArchCPU *)((void *)env - sizeof(CPUState)), \
+ const CPUArchState: \
+ (const ArchCPU *)((const void *)env - sizeof(CPUState)))
I was testing with a C17-ready compiler. Apparently C11 is ambiguous in
how it treats qualifiers inside _Generic:
../../target/arm/internals.h:1777:25: warning: due to lvalue conversion
of the controlling expression, association of type 'const CPUArchState'
(aka 'const struct CPUArchState') will never be selected because it is
qualified [-Wunreachable-code-generic-assoc]
1777 | const ARMCPU *cpu = env_archcpu(env);
| ^
include/exec/cpu-common.h:91:19: note: expanded from macro 'env_archcpu'
91 | const CPUArchState: \
| ^
Using typeof() makes it happier:
-- >8 --
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index d67d008236f..e3a5e40899f 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -87,6 +87,6 @@ static inline bool cpu_loop_exit_requested(const
CPUState *cpu)
*/
-#define env_archcpu(env) _Generic(*(env), \
- CPUArchState: \
+#define env_archcpu(env) _Generic(typeof(*env), \
+ typeof(CPUArchState): \
(ArchCPU *)((void *)env - sizeof(CPUState)), \
- const CPUArchState: \
+ typeof(const CPUArchState): \
(const ArchCPU *)((const void *)env - sizeof(CPUState)))
@@ -99,6 +99,6 @@ static inline bool cpu_loop_exit_requested(const
CPUState *cpu)
*/
-#define env_cpu(env) _Generic(*(env), \
- CPUArchState: \
+#define env_cpu(env) _Generic(typeof(*env), \
+ typeof(CPUArchState): \
(CPUState *)((void *)env - sizeof(CPUState)), \
- const CPUArchState: \
+ typeof(const CPUArchState): \
(const CPUState *)((const void *)env - sizeof(CPUState)))
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 372485a2e54..ee522e1e705 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -602,7 +602,7 @@ QEMU_BUILD_BUG_ON(offsetof(CPUState, neg) !=
*/
-#define cpu_env(cpu) _Generic(*(cpu), \
+#define cpu_env(cpu) _Generic(typeof(*cpu), \
/* We validate that CPUArchState follows CPUState in cpu-
target.c */ \
- CPUState: \
+ typeof(CPUState): \
(CPUArchState *)(cpu + 1), \
- const CPUState: \
+ typeof(const CPUState): \
(const CPUArchState *)(cpu + 1))
---
No, this now fails distinctly on Ubuntu 24.04:
In file included from ../accel/tcg/tcg-runtime.c:26:
../accel/tcg/tcg-runtime.c: In function ‘helper_exit_atomic’:
/home/runner/work/qemu/qemu/include/exec/cpu-common.h:100:31: error:
expected expression before ‘typeof’
100 | #define env_cpu(env) _Generic(typeof(*env), \
| ^~~~~~
../accel/tcg/tcg-runtime.c:135:26: note: in expansion of macro ‘env_cpu’
135 | cpu_loop_exit_atomic(env_cpu(env), GETPC());
| ^~~~~~~
I'm a bit clueless. In case you want to have a look, the
series is available here:
https://github.com/qualcomm/qemu/commits/refs/heads/philmd/cpu_has_work_const/
Thanks,
Phil.
