Reverting config path to system default if it doesn't find it.

docs/ssnes.1

@@ -55,6 +55,7 @@ Should this not be defined, \fBssnes\fR will look in platform specific paths to
 /etc/ssnes.cfg (when installed), or ssnes.cfg in the source tarball serves as a skeleton configuration file.
 If PATH is a directory, SSNES will treat this as the config file directory, where the state file name will be inferred from the rom name (*.cfg).
 When loading a rom from stdin, the path must be a full path, however.
+If a config cannot be found when using directory path, the default config path will be used instead.
 
 .IP
 Unix-like systems will look in $XDG_CONFIG_HOME/ssnes/ssnes.cfg first. Then it will try $HOME/.ssnes.cfg. Last, it will try /etc/ssnes.cfg. If no configuration is found, default settings will be assumed. A configuration file does not need to define every possible option, only those that should be overridden.

file.c

@@ -867,6 +867,17 @@ bool path_is_directory(const char *path)
 #endif
 }
 
+bool path_file_exists(const char *path)
+{
+   FILE *dummy = fopen(path, "rb");
+   if (dummy)
+   {
+      fclose(dummy);
+      return true;
+   }
+   return false;
+}
+
 void fill_pathname(char *out_path, const char *in_path, const char *replace, size_t size)
 {
    char tmp_path[strlen(in_path) + 1];

file.h

@@ -41,6 +41,7 @@ char** dir_list_new(const char *dir, const char *ext);
 void dir_list_free(char **dir_list);
 
 bool path_is_directory(const char *path);
+bool path_file_exists(const char *path);
 
 // Path-name operations.
 // Replaces filename extension with replace.

ssnes.c

@@ -686,6 +686,11 @@ static void parse_input(int argc, char *argv[])
       {
          fill_pathname_dir(g_extern.config_path, g_extern.basename, ".cfg", sizeof(g_extern.config_path));
          SSNES_LOG("Redirecting config file to \"%s\".\n", g_extern.config_path);
+         if (!path_file_exists(g_extern.config_path))
+         {
+            *g_extern.config_path = '\0';
+            SSNES_LOG("Did not find config file. Using system default.\n");
+         }
       }
    }
    else // Read ROM from stdin.