libxl: Make logging functions preserve errno

This is needed by the following patches.  It makes it much more
convenient for libxl functions to return the errno value from the
failure, when they fail.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>

diff --git a/tools/libxl/libxl_internal.c b/tools/libxl/libxl_internal.c
index f48e9eb109119ae334ea41f01bd455dca4f76c5d..4dcdabe6534c99e1dc99fc766cb1495b3d6280d8 100644 (file)
--- a/tools/libxl/libxl_internal.c
+++ b/tools/libxl/libxl_internal.c
@@ -156,11 +156,13 @@ void xl_logv(struct libxl_ctx *ctx, int loglevel, int errnoval,
 {
     char *enomem = "[out of memory formatting log message]";
     char *s;
-    int rc;
+    int rc, esave;
 
     if (!ctx->log_callback)
         return;
 
+    esave = errno;
+    
     rc = vasprintf(&s, fmt, ap);
     if (rc<0) { s = enomem; goto x; }
 
@@ -180,6 +182,7 @@ void xl_logv(struct libxl_ctx *ctx, int loglevel, int errnoval,
     ctx->log_callback(ctx->log_userdata, loglevel, file, line, func, s);
     if (s != enomem)
         free(s);
+    errno = esave;
 }
 
 void xl_log(struct libxl_ctx *ctx, int loglevel, int errnoval,

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 300c108bb4d0eb7c532834aaa0d1e6269d6b1fa7..10e72e520f2f4156fab51875ee88ae5bea5aed71 100644 (file)
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -47,6 +47,7 @@
 #define XL_LOG_ERRNO(ctx, loglevel, _f, _a...)
 #define XL_LOG_ERRNOVAL(ctx, loglevel, errnoval, _f, _a...)
 #endif
+  /* all of these macros preserve errno (saving and restoring) */
 
 #define XL_LOG_DEBUG 3
 #define XL_LOG_INFO 2
@@ -56,6 +57,7 @@
 /* logging */
 void xl_logv(struct libxl_ctx *ctx, int errnoval, int loglevel, const char *file, int line, const char *func, char *fmt, va_list al);
 void xl_log(struct libxl_ctx *ctx, int errnoval, int loglevel, const char *file, int line, const char *func, char *fmt, ...);
+  /* these functions preserve errno (saving and restoring) */
 
 
 typedef enum {