[Libguestfs] [PATCH nbdkit 1/3] server: log: Move preserve errno to log_verror function

[Richard W.M. Jones]

This neutral code refactoring just moves the place where we preserve
errno out one layer, but should have no other effect.
---
 server/internal.h   |  8 ++++----
 server/log-stderr.c |  9 ++-------
 server/log-syslog.c | 13 ++++---------
 server/log.c        | 12 ++++++++----
 4 files changed, 18 insertions(+), 24 deletions(-)

diff --git a/server/internal.h b/server/internal.h
index 0b0507e446..1a783e3fc0 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -340,10 +340,10 @@ extern void free_debug_flags (void);
 extern void log_verror (const char *fs, va_list args);
 
 /* log-*.c */
-extern void log_stderr_verror (const char *fs, va_list args)
-  ATTRIBUTE_FORMAT_PRINTF (1, 0);
-extern void log_syslog_verror (const char *fs, va_list args)
-  ATTRIBUTE_FORMAT_PRINTF (1, 0);
+extern void log_stderr_verror (int orig_errno, const char *fs, va_list args)
+  ATTRIBUTE_FORMAT_PRINTF (2, 0);
+extern void log_syslog_verror (int orig_errno, const char *fs, va_list args)
+  ATTRIBUTE_FORMAT_PRINTF (2, 0);
 
 /* vfprintf.c */
 #if !HAVE_VFPRINTF_PERCENT_M
diff --git a/server/log-stderr.c b/server/log-stderr.c
index 8a55f5df22..4d8b09da37 100644
--- a/server/log-stderr.c
+++ b/server/log-stderr.c
@@ -43,12 +43,9 @@
 
 #include "internal.h"
 
-/* Note: preserves the previous value of errno. */
 void
-log_stderr_verror (const char *fs, va_list args)
+log_stderr_verror (int orig_errno, const char *fs, va_list args)
 {
-  int err = errno;              /* must be first line of function */
-
   const char *name = threadlocal_get_name ();
   size_t instance_num = threadlocal_get_instance_num ();
   int tty;
@@ -69,7 +66,7 @@ log_stderr_verror (const char *fs, va_list args)
   }
 
   fprintf (stderr, "error: ");
-  errno = err;                  /* must restore in case fs contains %m */
+  errno = orig_errno;        /* must restore in case fs contains %m */
   vfprintf (stderr, fs, args);
   fprintf (stderr, "\n");
 
@@ -78,6 +75,4 @@ log_stderr_verror (const char *fs, va_list args)
 #ifdef HAVE_FUNLOCKFILE
   funlockfile (stderr);
 #endif
-
-  errno = err;                  /* must be last line of function */
 }
diff --git a/server/log-syslog.c b/server/log-syslog.c
index 76c5035b7d..29a7a8252f 100644
--- a/server/log-syslog.c
+++ b/server/log-syslog.c
@@ -45,11 +45,9 @@
 /* Tempted to use LOG_FTP instead of LOG_DAEMON! */
 static const int PRIORITY = LOG_DAEMON|LOG_ERR;
 
-/* Note: preserves the previous value of errno. */
 void
-log_syslog_verror (const char *fs, va_list args)
+log_syslog_verror (int orig_errno, const char *fs, va_list args)
 {
-  int err = errno;
   const char *name = threadlocal_get_name ();
   size_t instance_num = threadlocal_get_instance_num ();
   CLEANUP_FREE char *msg = NULL;
@@ -59,9 +57,9 @@ log_syslog_verror (const char *fs, va_list args)
   fp = open_memstream (&msg, &len);
   if (fp == NULL) {
     /* Fallback to logging using fs, args directly. */
-    errno = err; /* Must restore in case fs contains %m */
+    errno = orig_errno;      /* must restore in case fs contains %m */
     vsyslog (PRIORITY, fs, args);
-    goto out;
+    return;
   }
 
   if (name) {
@@ -71,12 +69,9 @@ log_syslog_verror (const char *fs, va_list args)
     fprintf (fp, ": ");
   }
 
-  errno = err; /* Must restore in case fs contains %m */
+  errno = orig_errno;        /* must restore in case fs contains %m */
   vfprintf (fp, fs, args);
   close_memstream (fp);
 
   syslog (PRIORITY, "%s", msg);
-
- out:
-  errno = err;
 }
diff --git a/server/log.c b/server/log.c
index 464e4f9a72..9c1f667a9b 100644
--- a/server/log.c
+++ b/server/log.c
@@ -46,23 +46,27 @@
 void
 log_verror (const char *fs, va_list args)
 {
+  int orig_errno = errno;
+
   switch (log_to) {
   case LOG_TO_DEFAULT:
     if (forked_into_background)
-      log_syslog_verror (fs, args);
+      log_syslog_verror (orig_errno, fs, args);
     else
-      log_stderr_verror (fs, args);
+      log_stderr_verror (orig_errno, fs, args);
     break;
   case LOG_TO_SYSLOG:
-    log_syslog_verror (fs, args);
+    log_syslog_verror (orig_errno, fs, args);
     break;
   case LOG_TO_STDERR:
-    log_stderr_verror (fs, args);
+    log_stderr_verror (orig_errno, fs, args);
     break;
   case LOG_TO_NULL:
     /* nothing */
     break;
   }
+
+  errno = orig_errno; /* Restore errno before leaving the function. */
 }
 
 /* Note: preserves the previous value of errno. */
-- 
2.44.0
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