Xen devel - Jan 2013 - [PATCH V3] libxc, libxenstore: make the headers C++-friendlier

Made the xenctrl.h and xenstore.h easier to use with C++:
added ''extern "C"'' statements, moved the definition
of
enum xc_error_code above it''s typedef, and renamed a
''new''
parameter (''new'' is a C++ keyword). Includes a modification
of _hvm_hw_fix_cpu() suggested by Jan Beulich.

Signed-off-by: Razvan Cojocaru <rzvncj@gmail.com>

diff -r 5af4f2ab06f3 -r f80587008e17 tools/libxc/xenctrl.h
--- a/tools/libxc/xenctrl.h	Tue Jan 22 09:33:10 2013 +0100
+++ b/tools/libxc/xenctrl.h	Wed Jan 23 16:41:30 2013 +0200
@@ -26,6 +26,10 @@
 #ifndef XENCTRL_H
 #define XENCTRL_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* Tell the Xen public headers we are a user-space tools build. */
 #ifndef __XEN_TOOLS__
 #define __XEN_TOOLS__ 1
@@ -114,6 +118,15 @@ typedef struct xc_interface_core xc_inte
 typedef struct xc_interface_core xc_evtchn;
 typedef struct xc_interface_core xc_gnttab;
 typedef struct xc_interface_core xc_gntshr;
+
+enum xc_error_code {
+  XC_ERROR_NONE = 0,
+  XC_INTERNAL_ERROR = 1,
+  XC_INVALID_KERNEL = 2,
+  XC_INVALID_PARAM = 3,
+  XC_OUT_OF_MEMORY = 4,
+  /* new codes need to be added to xc_error_level_to_desc too */
+};
 typedef enum xc_error_code xc_error_code;
 
 
@@ -1618,16 +1631,6 @@ int xc_hvm_inject_trap(
  *  LOGGING AND ERROR REPORTING
  */
 
-
-enum xc_error_code {
-  XC_ERROR_NONE = 0,
-  XC_INTERNAL_ERROR = 1,
-  XC_INVALID_KERNEL = 2,
-  XC_INVALID_PARAM = 3,
-  XC_OUT_OF_MEMORY = 4,
-  /* new codes need to be added to xc_error_level_to_desc too */
-};
-
 #define XC_MAX_ERROR_MSG_LEN 1024
 typedef struct xc_error {
   enum xc_error_code code;
@@ -2236,4 +2239,8 @@ int xc_compression_uncompress_page(xc_in
 				   unsigned long compbuf_size,
 				   unsigned long *compbuf_pos, char *dest);
 
+#ifdef __cplusplus
+}
+#endif 
+
 #endif /* XENCTRL_H */
diff -r 5af4f2ab06f3 -r f80587008e17 tools/xenstore/xenstore.h
--- a/tools/xenstore/xenstore.h	Tue Jan 22 09:33:10 2013 +0100
+++ b/tools/xenstore/xenstore.h	Wed Jan 23 16:41:30 2013 +0200
@@ -20,6 +20,10 @@
 #ifndef XENSTORE_H
 #define XENSTORE_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <xenstore_lib.h>
 
 #define XBT_NULL 0
@@ -244,6 +248,11 @@ char *xs_debug_command(struct xs_handle 
 		       void *data, unsigned int len);
 
 int xs_suspend_evtchn_port(int domid);
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* XENSTORE_H */
 
 /*
diff -r 5af4f2ab06f3 -r f80587008e17 xen/include/public/arch-x86/hvm/save.h
--- a/xen/include/public/arch-x86/hvm/save.h	Tue Jan 22 09:33:10 2013 +0100
+++ b/xen/include/public/arch-x86/hvm/save.h	Wed Jan 23 16:41:30 2013 +0200
@@ -268,16 +268,18 @@ struct hvm_hw_cpu_compat {
     uint32_t error_code;
 };
 
+union hvm_hw_cpu_union {
+    struct hvm_hw_cpu nat;
+    struct hvm_hw_cpu_compat cmp;
+};
+
 static inline int _hvm_hw_fix_cpu(void *h) {
-    struct hvm_hw_cpu *new=h;
-    struct hvm_hw_cpu_compat *old=h;
+    union hvm_hw_cpu_union *ucpu = (union hvm_hw_cpu_union *)h;
 
-    /* If we copy from the end backwards, we should
-     * be able to do the modification in-place */
-    new->error_code=old->error_code;
-    new->pending_event=old->pending_event;
-    new->tsc=old->tsc;
-    new->msr_tsc_aux=0;
+    ucpu->nat.error_code = ucpu->cmp.error_code;
+    ucpu->nat.pending_event = ucpu->cmp.pending_event;
+    ucpu->nat.tsc = ucpu->cmp.tsc;
+    ucpu->nat.msr_tsc_aux = 0;
 
     return 0;
 }

>>> On 23.01.13 at 15:43, Razvan Cojocaru <rzvncj@gmail.com>
wrote:
> --- a/xen/include/public/arch-x86/hvm/save.h	Tue Jan 22 09:33:10 2013 +0100
> +++ b/xen/include/public/arch-x86/hvm/save.h	Wed Jan 23 16:41:30 2013 +0200
> @@ -268,16 +268,18 @@ struct hvm_hw_cpu_compat {
>      uint32_t error_code;
>  };
>  
> +union hvm_hw_cpu_union {
> +    struct hvm_hw_cpu nat;
> +    struct hvm_hw_cpu_compat cmp;
> +};
I would think that specifically in C++ you don''t want this type to
be visible at global scope. Please move it into the function below.
> +
>  static inline int _hvm_hw_fix_cpu(void *h) {
> -    struct hvm_hw_cpu *new=h;
> -    struct hvm_hw_cpu_compat *old=h;
> +    union hvm_hw_cpu_union *ucpu = (union hvm_hw_cpu_union *)h;
>  
> -    /* If we copy from the end backwards, we should
> -     * be able to do the modification in-place */
Don''t drop this comment, please. The changes, as indicated earlier,
make it match actual behavior.

Also, just in case you aren''t aware: Posting patches that touch both
tools and hypervisor files makes it more cumbersome to get them
applied (due to different people being responsible), so whenever
you can you should try to split patches accordingly - in the case here
it''s obviously unnecessary to keep the pieces together in a single
patch.

Finally, from the very beginning the title of your patch was
suggesting the patch would touch tools code only. You should
avoid giving such false impressions. I wouldn''t even have looked
at it (which you probably would have liked) if the rest of the
subject didn''t get me curious.

Jan
> -    new->error_code=old->error_code;
> -    new->pending_event=old->pending_event;
> -    new->tsc=old->tsc;
> -    new->msr_tsc_aux=0;
> +    ucpu->nat.error_code = ucpu->cmp.error_code;
> +    ucpu->nat.pending_event = ucpu->cmp.pending_event;
> +    ucpu->nat.tsc = ucpu->cmp.tsc;
> +    ucpu->nat.msr_tsc_aux = 0;
>  
>      return 0;
>  }