I'm running a few flowwatches and piping their output to a flex
program to process the data. That is, I invoke flowwatch like this
bash-2.03$ flowwatch <filter> | mytool &
where mytool was compiled from lex.yy.c, which in turn was generated
a lex source file.
This is working fine except for some cases in which the filter causes
flowwtach to generate very few output.
In these cases mytool dies (no core dump) and all I get is the message
"input in flex scanner failed" to the screen.
I've seen http://compilers.iecc.com/comparch/article/99-05-049 .
And I checked lex.yy.c and the only place where this message can be
/* Gets input and stuffs it into "buf". number of characters read, or
* is returned in "result".
#define YY_INPUT(buf,result,max_size) \
if ( yy_current_buffer->yy_is_interactive ) \
int c = '*', n; \
for ( n = 0; n < max_size && \
(c = getc( yyin )) != EOF && c != '\n'; ++n
buf[n] = (char) c; \
if ( c == '\n' ) \
buf[n++] = (char) c; \
if ( c == EOF && ferror( yyin ) ) \
YY_FATAL_ERROR( "input in flex scanner failed"
result = n; \
else if ( ((result = fread( buf, 1, max_size, yyin )) == 0) \
&& ferror( yyin ) ) \
YY_FATAL_ERROR( "input in flex scanner failed" );
So for the message to happen, ferror( yyin) must be non zero.
Does anyone know why is this so ??
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