arch/riscv: 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.

Remove extern "C" support from files that don't declare objects or
functions.

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/riscv/include/kernel_arch_data.h

@@ -15,10 +15,6 @@
 #ifndef ZEPHYR_ARCH_RISCV_INCLUDE_KERNEL_ARCH_DATA_H_
 #define ZEPHYR_ARCH_RISCV_INCLUDE_KERNEL_ARCH_DATA_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <toolchain.h>
 #include <linker/sections.h>
 #include <arch/cpu.h>
@@ -31,8 +27,16 @@ extern "C" {
 #include <sys/dlist.h>
 #include <kernel_internal.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 extern K_THREAD_STACK_DEFINE(_interrupt_stack, CONFIG_ISR_STACK_SIZE);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _ASMLANGUAGE */
 
 #endif /* ZEPHYR_ARCH_RISCV_INCLUDE_KERNEL_ARCH_DATA_H_ */

include/arch/riscv/arch.h

@@ -24,10 +24,6 @@
 #include <soc.h>
 #include <generated_dts_board.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* stacks, for RISCV architecture stack should be 16byte-aligned */
 #define STACK_ALIGN  16
 
@@ -46,6 +42,10 @@ extern "C" {
 #ifndef _ASMLANGUAGE
 #include <sys/util.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define STACK_ROUND_UP(x) ROUND_UP(x, STACK_ALIGN)
 #define STACK_ROUND_DOWN(x) ROUND_DOWN(x, STACK_ALIGN)
 
@@ -157,14 +157,15 @@ static ALWAYS_INLINE void arch_nop(void)
 extern u32_t z_timer_cycle_get_32(void);
 #define z_arch_k_cycle_get_32()	z_timer_cycle_get_32()
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /*_ASMLANGUAGE */
 
 #if defined(CONFIG_SOC_FAMILY_RISCV_PRIVILEGE)
 #include <arch/riscv/riscv-privilege/asm_inline.h>
 #endif
 
-#ifdef __cplusplus
-}
-#endif
 
 #endif

include/arch/riscv/exp.h

@@ -15,10 +15,6 @@
 #ifndef ZEPHYR_INCLUDE_ARCH_RISCV_EXP_H_
 #define ZEPHYR_INCLUDE_ARCH_RISCV_EXP_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #ifndef _ASMLANGUAGE
 #include <zephyr/types.h>
 #include <toolchain.h>
@@ -27,6 +23,10 @@ extern "C" {
 #include <soc_context.h>
 #endif
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*
  * The name of the structure which contains soc-specific state, if
  * any, as well as the soc_esf_t typedef below, are part of the RISC-V
@@ -75,10 +75,11 @@ typedef struct __esf z_arch_esf_t;
 #ifdef CONFIG_RISCV_SOC_CONTEXT_SAVE
 typedef struct soc_esf soc_esf_t;
 #endif
-#endif /* _ASMLANGUAGE */
 
 #ifdef __cplusplus
 }
 #endif
 
+#endif /* _ASMLANGUAGE */
+
 #endif /* ZEPHYR_INCLUDE_ARCH_RISCV_EXP_H_ */

include/arch/riscv/riscv-privilege/asm_inline_gcc.h

@@ -7,10 +7,6 @@
 #ifndef ZEPHYR_INCLUDE_ARCH_RISCV_RISCV_PRIVILEGE_ASM_INLINE_GCC_H_
 #define ZEPHYR_INCLUDE_ARCH_RISCV_RISCV_PRIVILEGE_ASM_INLINE_GCC_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /*
  * The file must not be included directly
  * Include arch/cpu.h instead
@@ -21,11 +17,6 @@ extern "C" {
 
 #include <toolchain.h>
 
-
 #endif /* _ASMLANGUAGE */
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* ZEPHYR_INCLUDE_ARCH_RISCV_RISCV_PRIVILEGE_ASM_INLINE_GCC_H_ */