arch/xtensa: rearrange for standard use of extern "C"

Consistently place C++ use of extern "C" after all include directives,
within the negative branch of _ASMLANGUAGE if used.

Background from issue #17997:

Declarations that use C linkage should be placed within extern "C"
so the language linkage is correct when the header is included by
a C++ compiler.

Similarly #include directives should be outside the extern "C" to
ensure the language-specific default linkage is applied to any
declarations provided by the included header.

See: https://en.cppreference.com/w/cpp/language/language_linkage
Signed-off-by: Peter Bigot <[email protected]>

Author: pabigot

arch/xtensa/include/kernel_arch_data.h

@@ -20,22 +20,26 @@
 #ifndef ZEPHYR_ARCH_XTENSA_INCLUDE_KERNEL_ARCH_DATA_H_
 #define ZEPHYR_ARCH_XTENSA_INCLUDE_KERNEL_ARCH_DATA_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <toolchain.h>
 #include <linker/sections.h>
 #include <arch/cpu.h>
 #include <kernel_arch_thread.h>
 
+/* stacks */
+#define STACK_ROUND_UP(x) ROUND_UP(x, STACK_ALIGN_SIZE)
+#define STACK_ROUND_DOWN(x) ROUND_DOWN(x, STACK_ALIGN_SIZE)
+
 #if !defined(_ASMLANGUAGE) && !defined(__ASSEMBLER__)
 #include <kernel.h>            /* public kernel API */
 #include <kernel_internal.h>
 #include <zephyr/types.h>
 #include <sys/dlist.h>
 #include <sys/util.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* Bitmask definitions for the struct k_thread->flags bit field */
 
 /* executing context is interrupt handler */
@@ -47,20 +51,15 @@ extern "C" {
 
 typedef struct __esf __esf_t;
 
-#endif /*! _ASMLANGUAGE && ! __ASSEMBLER__ */
-
 #ifdef CONFIG_USE_SWITCH
 void xtensa_switch(void *switch_to, void **switched_from);
 #define z_arch_switch xtensa_switch
 #endif
 
-/* stacks */
-#define STACK_ROUND_UP(x) ROUND_UP(x, STACK_ALIGN_SIZE)
-#define STACK_ROUND_DOWN(x) ROUND_DOWN(x, STACK_ALIGN_SIZE)
-
 #ifdef __cplusplus
 }
 #endif
 
-#endif /* ZEPHYR_ARCH_XTENSA_INCLUDE_KERNEL_ARCH_DATA_H_ */
+#endif /*! _ASMLANGUAGE && ! __ASSEMBLER__ */
 
+#endif /* ZEPHYR_ARCH_XTENSA_INCLUDE_KERNEL_ARCH_DATA_H_ */

arch/xtensa/include/kernel_arch_func.h

@@ -12,6 +12,7 @@
 #ifndef _ASMLANGUAGE
 #include <string.h>
 #include <stdbool.h>
+#include <stddef.h> /* For size_t */
 
 #ifdef __cplusplus
 extern "C" {
@@ -119,8 +120,6 @@ z_set_thread_return_value(struct k_thread *thread, unsigned int value)
 
 extern void k_cpu_atomic_idle(unsigned int key);
 
-#include <stddef.h> /* For size_t */
-
 #ifdef __cplusplus
 }
 #endif

arch/xtensa/include/xtensa_config.h

@@ -6,10 +6,6 @@
 #ifndef ZEPHYR_ARCH_XTENSA_INCLUDE_XTENSA_CONFIG_H_
 #define ZEPHYR_ARCH_XTENSA_INCLUDE_XTENSA_CONFIG_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <xtensa/hal.h>
 #include <xtensa/config/core.h>
 #include <xtensa/config/system.h>	/* required for XSHAL_CLIB */
@@ -133,9 +129,4 @@ extern "C" {
 #define XT_STACK_EXTRA_CLIB         (XT_XTRA_SIZE + XT_CLIB_CONTEXT_AREA_SIZE)
 
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* ZEPHYR_ARCH_XTENSA_INCLUDE_XTENSA_CONFIG_H_ */
-

arch/xtensa/include/xtensa_context.h

@@ -19,15 +19,18 @@
 #ifndef ZEPHYR_ARCH_XTENSA_INCLUDE_XTENSA_CONTEXT_H_
 #define ZEPHYR_ARCH_XTENSA_INCLUDE_XTENSA_CONTEXT_H_
 
-#ifdef __ASSEMBLER__
-#include    <xtensa/coreasm.h>
-#endif
-
 #include    <xtensa/config/tie.h>
 #include    <xtensa/corebits.h>
 #include    <xtensa/config/system.h>
 #include    <xtensa/xtruntime-frames.h>
 
+#ifdef __ASSEMBLER__
+#include    <xtensa/coreasm.h>
+#else /* __ASSEMBLER__ */
+#ifdef __cplusplus
+extern "C" {
+#endif
+#endif /* __ASSEMBLER__ */
 
 /* Align a value up to nearest n-byte boundary, where n is a power of 2. */
 #define ALIGNUP(n, val) (((val) + (n)-1) & -(n))
@@ -310,8 +313,11 @@ ret
 #define RET(sz)       retw
 #define RET0          retw
 #endif /* __XTENSA_CALL0_ABI__ */
+#else /* __ASSEMBLER__ */
+#ifdef __cplusplus
+}
+#endif
 #endif /* __ASSEMBLER__ */
 
 
 #endif /* ZEPHYR_ARCH_XTENSA_INCLUDE_XTENSA_CONTEXT_H_ */
-

include/arch/xtensa/arch.h

@@ -15,10 +15,6 @@
 
 #include <irq.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <generated_dts_board.h>
 #if !defined(_ASMLANGUAGE) && !defined(__ASSEMBLER__)
 #include <arch/common/sys_io.h>
@@ -36,6 +32,10 @@ extern "C" {
 
 #include <arch/xtensa/exc.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* internal routine documented in C file, needed by IRQ_CONNECT() macro */
 extern void z_irq_priority_set(u32_t irq, u32_t prio, u32_t flags);
 
@@ -95,9 +95,10 @@ static ALWAYS_INLINE void arch_nop(void)
 	__asm__ volatile("nop");
 }
 
-#endif /* !defined(_ASMLANGUAGE) && !defined(__ASSEMBLER__)  */
 #ifdef __cplusplus
 }
 #endif
 
+#endif /* !defined(_ASMLANGUAGE) && !defined(__ASSEMBLER__)  */
+
 #endif /* ZEPHYR_INCLUDE_ARCH_XTENSA_ARCH_H_ */