log: add ssh_vlog to save the stack space

and add LOG_SIZE macro to control the buffer size

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
Change-Id: I3eaeea001fc531fdb55074fc3a9d140b27847c1f

include/libssh/libssh.h

@@ -49,6 +49,8 @@
   #endif
 #endif
 
+#include <stdarg.h>
+
 #ifdef _MSC_VER
   /* Visual Studio hasn't inttypes.h so it doesn't know uint32_t */
   typedef int int32_t;
@@ -587,6 +589,10 @@ LIBSSH_API int ssh_set_log_level(int level);
 LIBSSH_API int ssh_get_log_level(void);
 LIBSSH_API void *ssh_get_log_userdata(void);
 LIBSSH_API int ssh_set_log_userdata(void *data);
+LIBSSH_API void ssh_vlog(int verbosity,
+                         const char *function,
+                         const char *format,
+                         va_list *va) PRINTF_ATTRIBUTE(3, 0);
 LIBSSH_API void _ssh_log(int verbosity,
                          const char *function,
                          const char *format, ...) PRINTF_ATTRIBUTE(3, 4);

include/libssh/libsshpp.hpp

@@ -369,13 +369,11 @@ public:
     return state;
   }
   void log(int priority, const char *format, ...){
-    char buffer[1024];
     va_list va;
 
     va_start(va, format);
-    vsnprintf(buffer, sizeof(buffer), format, va);
+    ssh_vlog(priority, "libsshpp", format, &va);
     va_end(va);
-    _ssh_log(priority, "libsshpp", "%s", buffer);
   }
 
   /** @brief copies options from a session to another

src/libssh.map

@@ -405,6 +405,7 @@ LIBSSH_4_5_0    # Released
         ssh_userauth_publickey_auto_get_current_identity;
         ssh_userauth_try_publickey;
         ssh_version;
+        ssh_vlog;
         ssh_write_knownhost;
         string_burn;
         string_copy;

src/log.c

@@ -38,6 +38,10 @@
 #include "libssh/misc.h"
 #include "libssh/session.h"
 
+#ifndef LOG_SIZE
+#define LOG_SIZE 1024
+#endif
+
 static LIBSSH_THREAD int ssh_log_level;
 static LIBSSH_THREAD ssh_logging_callback ssh_log_cb;
 static LIBSSH_THREAD void *ssh_log_userdata;
@@ -94,38 +98,52 @@ static void ssh_log_stderr(int verbosity,
     fprintf(stderr, "  %s\n", buffer);
 }
 
+static void ssh_log_custom(ssh_logging_callback log_fn,
+                           int verbosity,
+                           const char *function,
+                           const char *buffer)
+{
+    char buf[LOG_SIZE + 64];
+
+    snprintf(buf, sizeof(buf), "%s: %s", function, buffer);
+    log_fn(verbosity, function, buf, ssh_get_log_userdata());
+}
+
 void ssh_log_function(int verbosity,
                       const char *function,
                       const char *buffer)
 {
     ssh_logging_callback log_fn = ssh_get_log_callback();
+
     if (log_fn) {
-        char buf[1024];
+        ssh_log_custom(log_fn, verbosity, function, buffer);
-
-        snprintf(buf, sizeof(buf), "%s: %s", function, buffer);
-
-        log_fn(verbosity,
-               function,
-               buf,
-               ssh_get_log_userdata());
         return;
     }
 
     ssh_log_stderr(verbosity, function, buffer);
 }
 
+void ssh_vlog(int verbosity,
+              const char *function,
+              const char *format,
+              va_list *va)
+{
+    char buffer[LOG_SIZE];
+
+    vsnprintf(buffer, sizeof(buffer), format, *va);
+    ssh_log_function(verbosity, function, buffer);
+}
+
 void _ssh_log(int verbosity,
               const char *function,
               const char *format, ...)
 {
-    char buffer[1024];
     va_list va;
 
     if (verbosity <= ssh_get_log_level()) {
         va_start(va, format);
-        vsnprintf(buffer, sizeof(buffer), format, va);
+        ssh_vlog(verbosity, function, format, &va);
         va_end(va);
-        ssh_log_function(verbosity, function, buffer);
     }
 }
 
@@ -135,14 +153,12 @@ void ssh_log(ssh_session session,
              int verbosity,
              const char *format, ...)
 {
-  char buffer[1024];
   va_list va;
 
   if (verbosity <= session->common.log_verbosity) {
     va_start(va, format);
-    vsnprintf(buffer, sizeof(buffer), format, va);
+    ssh_vlog(verbosity, "", format, &va);
     va_end(va);
-    ssh_log_function(verbosity, "", buffer);
   }
 }
 
@@ -157,14 +173,12 @@ void ssh_log_common(struct ssh_common_struct *common,
                     const char *function,
                     const char *format, ...)
 {
-    char buffer[1024];
     va_list va;
 
     if (verbosity <= common->log_verbosity) {
         va_start(va, format);
-        vsnprintf(buffer, sizeof(buffer), format, va);
+        ssh_vlog(verbosity, function, format, &va);
         va_end(va);
-        ssh_log_function(verbosity, function, buffer);
     }
 }