utils: drop strtok_r from envlist_parse

The problem is that mingw 4.9.1 fails to compile the code with the
following warning:

/mingw/include/string.h:88:9: note: previous declaration of 'strtok_r'
was here
   char *strtok_r(char * __restrict__ _Str,
                  const char * __restrict__ _Delim,
                  char ** __restrict__ __last);
/include/sysemu/os-win32.h:83:7: warning: redundant redeclaration of
   'strtok_r' [-Wredundant-decls]
   char *strtok_r(char *str, const char *delim, char **saveptr);

The problem is that compiles just fine on previous versions of mingw.
Compiler version check here is not a good idea. Though fortunately
strtok_r is used only once in the code and we could simply rewrite
the code without it.

Signed-off-by: Olga Krishtal <okrishtal@parallels.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Eric Blake <eblake@redhat.com>
CC: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

include/sysemu/os-win32.h

diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h
index af3fbc4..9cc9e08 100644
--- a/include/sysemu/os-win32.h
+++ b/include/sysemu/os-win32.h
@@ -81,7 +81,6 @@
 #undef localtime_r
 struct tm *localtime_r(const time_t *timep, struct tm *result);
 
-char *strtok_r(char *str, const char *delim, char **saveptr);
 
 static inline void os_setup_signal_handling(void) {}
 static inline void os_daemonize(void) {}

util/envlist.c

diff --git a/util/envlist.c b/util/envlist.c
index ebc06cf..099a544 100644
--- a/util/envlist.c
+++ b/util/envlist.c
@@ -94,30 +94,30 @@
 {
 	char *tmpenv, *envvar;
 	char *envsave = NULL;
-
-	assert(callback != NULL);
+    int ret = 0;
+    assert(callback != NULL);
 
 	if ((envlist == NULL) || (env == NULL))
 		return (EINVAL);
 
-	/*
-	 * We need to make temporary copy of the env string
-	 * as strtok_r(3) modifies it while it tokenizes.
-	 */
 	if ((tmpenv = strdup(env)) == NULL)
 		return (errno);
+    envsave = tmpenv;
 
-	envvar = strtok_r(tmpenv, ",", &envsave);
-	while (envvar != NULL) {
-		if ((*callback)(envlist, envvar) != 0) {
-			free(tmpenv);
-			return (errno);
+    do {
+        envvar = strchr(tmpenv, ',');
+        if (envvar != NULL) {
+            *envvar = '\0';
+        }
+        if ((*callback)(envlist, tmpenv) != 0) {
+            ret = errno;
+            break;
 		}
-		envvar = strtok_r(NULL, ",", &envsave);
-	}
+        tmpenv = envvar + 1;
+    } while (envvar != NULL);
 
-	free(tmpenv);
-	return (0);
+    free(envsave);
+    return ret;
 }
 
 /*