Emit also queue overflow error (issue #66)

Jan Breuer

2016-02-14 a79e3f82d6c19f9991327444ea156380801bffda

 libscpi/inc/scpi/expression.h

@@ -41,7 +41,7 @@
#ifdef __cplusplus
extern "C" {
#endif
    

    enum _scpi_expr_result_t {
        SCPI_EXPR_OK = 0,
        SCPI_EXPR_ERROR,