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POuse bison to make executable file but error
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  1. POuse bison to make executable file but error
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    copied!<p>I followed the <a href="http://aquamentus.com/flex_bison.html" rel="nofollow">Flex and Bison tutorial</a> to learn flex &amp; bison , but I'm stuck. When I compile with "g++ snazzle.tab.c lex.yy.c -lfl -o snazzle", I get these error messages:</p> <pre><code> snazzle.tab.c: In function ‘int yyparse()’: snazzle.tab.c:1403: warning: deprecated conversion from string constant to ‘char*’ snazzle.tab.c:1546: warning: deprecated conversion from string constant to ‘char*’ /tmp/ccFyBCBm.o: In function `yyparse': snazzle.tab.c:(.text+0x1e0): undefined reference to `yylex' collect2: ld returned 1 exit status </code></pre> <p>my env is ubuntu 10.04 bison 2.4.1 flex 2.5.35</p> <p>I still can not find the problem. first I compile with "bison -o snazzle.y", then it generate two snazzle.tab.c and snazzle.tab.h respectively. finally I compile with "g++ snazzle.tab.c lex.yy.c -lfl -o snazzle". my code as follew : </p> <pre><code>snazzle.l %{ #include &lt;cstdio&gt; #include &lt;iostream&gt; using namespace std; #include "snazzle.tab.h" %} %% [ \t] ; [0-9]+\.[0-9]+ { yylval.fval = atof(yytext); return FLOAT; } [0-9]+ { yylval.ival = atoi(yytext); return INT; } [a-zA-Z0-9]+ { // we have to copy because we can't rely on yytext not changing underneath us: yylval.sval = strdup(yytext); return STRING; } . ; %% </code></pre> <hr> <pre><code>snazzle.y %{ #include &lt;cstdio&gt; #include &lt;iostream&gt; using namespace std; extern "C" int yylex(); extern "C" int yyparse(); extern "C" FILE *yyin; void yyerror(char *s); %} %union { int ival; float fval; char *sval; } %token &lt;ival&gt; INT %token &lt;fval&gt; FLOAT %token &lt;sval&gt; STRING %% snazzle: INT snazzle { cout &lt;&lt; "bison found an int: " &lt;&lt; $1 &lt;&lt; endl; } | FLOAT snazzle { cout &lt;&lt; "bison found a float: " &lt;&lt; $1 &lt;&lt; endl; } | STRING snazzle { cout &lt;&lt; "bison found a string: " &lt;&lt; $1 &lt;&lt; endl; } | INT { cout &lt;&lt; "bison found an int: " &lt;&lt; $1 &lt;&lt; endl; } | FLOAT { cout &lt;&lt; "bison found a float: " &lt;&lt; $1 &lt;&lt; endl; } | STRING { cout &lt;&lt; "bison found a string: " &lt;&lt; $1 &lt;&lt; endl; } ; %% main() { // open a file handle to a particular file: FILE *myfile = fopen("a.snazzle.file", "r"); // make sure it is valid: if (!myfile) { cout &lt;&lt; "I can't open a.snazzle.file!" &lt;&lt; endl; return -1; } // set flex to read from it instead of defaulting to STDIN: yyin = myfile; // parse through the input until there is no more: do { yyparse(); } while (!feof(yyin)); } void yyerror(char *s) { cout &lt;&lt; "EEK, parse error! Message: " &lt;&lt; s &lt;&lt; endl; // might as well halt now: exit(-1); } </code></pre>
 

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