resolve #1990170

1 files changed, 1 insertions, 1 deletions

diff --git a/flex.skl b/flex.skl
index 80fa8b1..60c141f 100644
--- a/flex.skl
+++ b/flex.skl
@@ -1078,7 +1078,7 @@ m4_ifdef( [[M4_YY_NOT_IN_HEADER]],
 /* This used to be an fputs(), but since the string might contain NUL's,
  * we now use fwrite().
  */
-#define ECHO fwrite( yytext, yyleng, 1, yyout )
+#define ECHO do { if (fwrite( yytext, yyleng, 1, yyout )) {} } while (0)
 %endif
 %if-c++-only C++ definition
 #define ECHO LexerOutput( yytext, yyleng )