A fatal error occurred v4.2.0: Illegal length modifier specified 'f' in s[np]printf call

Lukas · February 23, 2021, 4:46pm

Hi,

It would be great if you would like to get to the source of this issue. Very few people report it, but still it has been reported before:

I personally think this isn’t a bug in Matomo or even in Twig, but rather a bug in your PHP version.

This is the line of code that the error message says:

github.com

twigphp/Twig/blob/1f3b7e2c06cc05d42936a8ad508ff1db7975cdc5/src/Cache/FilesystemCache.php#L61


      
                  clearstatcache(true, $dir);
                  if (!is_dir($dir)) {
                      throw new \RuntimeException(sprintf('Unable to create the cache directory (%s).', $dir));
                  }
              }
          } elseif (!is_writable($dir)) {
              throw new \RuntimeException(sprintf('Unable to write in the cache directory (%s).', $dir));
          }
          
          $tmpFile = tempnam($dir, basename($key));
          if (false !== @file_put_contents($tmpFile, $content) && @rename($tmpFile, $key)) {
              @chmod($key, 0666 & ~umask());
          
              if (self::FORCE_BYTECODE_INVALIDATION == ($this->options & self::FORCE_BYTECODE_INVALIDATION)) {
                  // Compile cached file into bytecode cache
                  if (\function_exists('opcache_invalidate') && filter_var(ini_get('opcache.enable'), FILTER_VALIDATE_BOOLEAN)) {
                      @opcache_invalidate($key, true);
                  } elseif (\function_exists('apc_compile_file')) {
                      apc_compile_file($key);
                  }
              }

As you can see it includes no kind of call to *printf, so there can’t be an illegal modifier passed to it.

But I wouldn’t be surprised if the C code that implements file_put_contents and rename do internally use printf in a way that breaks in exactly your environment and in exactly the way Matomo uses it (as I can find few references to it outside Matomo on the internet).

My recommendation would be to upgrade your PHP to the latest patch version (so the y in 7.x.y) and see if it still occurs.