Hi all!
Here is a simple lexer which works with flex-2.5.2 but not with
flex-2.5.4. Is this a bug in flex-2.5.4 or is 2.5.4 stricter,
revealing a bug in my code?
This simple lexer replaces "foo" with "bar" (just to do something) and
strips out comments delimited by '<' and '>'. (In real life I am
looking for C-style comments, but single character delimiters yield a
simpler example.) It works with flex-2.5.2 but with flex-2.5.4 it
blows up following the input() call which returns EOF.
There was a similar bug in flex-2.5.3, but the NEWS file that comes
with 2.5.4 says:
************************************************************
Changes between release 2.5.4 (11Sep96) and release 2.5.3:
- Fixed a bug introduced in 2.5.3 that blew it when a call
to input() occurred at the end of an input file.
[snip to end]
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I have Debian 1.2 installed, giving me flex-2.5.2. I built flex-2.5.4
directly from the GNU package. Could someone running bo or hamm
verify that this lexer breaks with the Debain flex-2.5.4 package, and
could someone who knows a little more than I do about flex tell me if
I am screwing something up. If my code looks OK I will submit a bug
report.
(I discovered this problem on an RS/6000 where I have an immediate need
for a working flex. I could not locate flex-2.5.2 on the net, but was
happy to find the source on the rex CD in my laptop.)
Kirk Hilliard
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$ flex --version
flex version 2.5.2
$ ./flex-2.5.4 --version
./flex-2.5.4 version 2.5.4
$ cat foo.l
%array
%option noyywrap
%%
"<" { int c;
while ( (c = input()) != '>' && c != EOF )
; /* eat up text of comment */
if ( c == EOF ) printf( "\n" "error: EOF in comment\n" );
}
foo printf("bar");
%%
void main(int argc, char **argv) {
YY_BUFFER_STATE ybsInputBuffer;
while(--argc) {
ybsInputBuffer = yy_scan_string(*++argv);
yylex();
yy_delete_buffer(ybsInputBuffer);
putchar('\n');
}
} /* main */
$ flex foo.l
$ gcc lex.yy.c
$ ./a.out "foo<bleh>bar" "foo<bleh" "foo<bleh>bell"
barbar
bar
error: EOF in comment
barbell
$ ./flex-2.5.4 foo.l
$ gcc lex.yy.c
$ ./a.out "foo<bleh>bar" "foo<bleh" "foo<bleh>bell"
barbar
bar
error: EOF in comment
input in flex scanner failed
$
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