arch: riscv: Fix warning when C++ is enabled
When compiling with C++ enabled (CONFIG_CPP), add an unused member to
prevent an empty struct; this makes the struct size the same for both C
and C++.
Fixes the following warnings:
In file included from include/zephyr/drivers/gpio.h:22:
In file included from include/zephyr/tracing/tracing.h:9:
In file included from include/zephyr/kernel.h:17:
In file included from include/zephyr/kernel_includes.h:32:
In file included from include/zephyr/kernel_structs.h:29:
In file included from include/zephyr/arch/structs.h:29:
include/zephyr/arch/riscv/structs.h:11:1: error: empty struct has size 0
in C, size 1 in C++ [-Werror,-Wextern-c-compat]
11 | struct _cpu_arch {
| ^
In file included from include/zephyr/drivers/gpio.h:22:
In file included from include/zephyr/tracing/tracing.h:9:
In file included from include/zephyr/kernel.h:17:
In file included from include/zephyr/kernel_includes.h:36:
In file included from include/zephyr/arch/cpu.h:25:
In file included from include/zephyr/arch/riscv/arch.h:18:
include/zephyr/arch/riscv/thread.h:68:1: error: empty struct has size 0
in C, size 1 in C++ [-Werror,-Wextern-c-compat]
68 | struct _thread_arch {
| ^
Signed-off-by: Tom Hughes <tomhughes@chromium.org>
diff --git a/include/zephyr/arch/riscv/structs.h b/include/zephyr/arch/riscv/structs.h
index 11e4935..691b67a 100644
--- a/include/zephyr/arch/riscv/structs.h
+++ b/include/zephyr/arch/riscv/structs.h
@@ -22,6 +22,15 @@
atomic_ptr_val_t fpu_owner;
uint32_t fpu_state;
#endif
+#if defined(CONFIG_CPP) && !defined(CONFIG_USERSPACE) && \
+ !(defined(CONFIG_SMP) || (CONFIG_MP_MAX_NUM_CPUS > 1)) && !defined(CONFIG_FPU_SHARING)
+ /* Empty struct has size 0 in C, size 1 in C++. Force them to be the same. */
+ uint8_t unused_cpp_size_compatibility;
+#endif
};
+#if defined(CONFIG_CPP)
+BUILD_ASSERT(sizeof(struct _cpu_arch) >= 1);
+#endif
+
#endif /* ZEPHYR_INCLUDE_RISCV_STRUCTS_H_ */
diff --git a/include/zephyr/arch/riscv/thread.h b/include/zephyr/arch/riscv/thread.h
index 8137668..2ae6f5c 100644
--- a/include/zephyr/arch/riscv/thread.h
+++ b/include/zephyr/arch/riscv/thread.h
@@ -82,8 +82,17 @@
unsigned long m_mode_pmpaddr_regs[CONFIG_PMP_SLOTS];
unsigned long m_mode_pmpcfg_regs[CONFIG_PMP_SLOTS / sizeof(unsigned long)];
#endif
+#if defined(CONFIG_CPP) && !defined(CONFIG_FPU_SHARING) && !defined(CONFIG_USERSPACE) && \
+ !defined(CONFIG_PMP_STACK_GUARD)
+ /* Empty struct has size 0 in C, size 1 in C++. Force them to be the same. */
+ uint8_t unused_cpp_size_compatibility;
+#endif
};
+#if defined(CONFIG_CPP)
+BUILD_ASSERT(sizeof(struct _thread_arch) >= 1);
+#endif
+
typedef struct _thread_arch _thread_arch_t;
#endif /* _ASMLANGUAGE */
