Implementing eval and load functions inside a scripting engine with Flex and Bison.
- by Simone Margaritelli
Hy guys, i'm developing a scripting engine with flex and bison and now
i'm implementing the eval and load functions for this language.
Just to give you an example, the syntax is like :
import std.*;
load( "some_script.hy" );
eval( "foo = 123;" );
println( foo );
So, in my lexer i've implemented the function :
void hyb_parse_string( const char *str ){
extern int yyparse(void);
YY_BUFFER_STATE prev, next;
/*
* Save current buffer.
*/
prev = YY_CURRENT_BUFFER;
/*
* yy_scan_string will call yy_switch_to_buffer.
*/
next = yy_scan_string( str );
/*
* Do actual parsing (yyparse calls yylex).
*/
yyparse();
/*
* Restore previous buffer.
*/
yy_switch_to_buffer(prev);
}
But it does not seem to work.
Well, it does but when the string (loaded from a file or directly
evaluated) is finished, i get a sigsegv :
Program received signal SIGSEGV, Segmentation fault.
0xb7f2b801 in yylex () at src/lexer.cpp:1658
1658 if ( YY_CURRENT_BUFFER_LVALUE->yy_buffer_status == YY_BUFFER_NEW )
As you may notice, the sigsegv is generated by the flex/bison code,
not mine ... any hints, or at least any example on how to implement those kind of functions?
PS: I've succesfully implemented the include directive, but i need eval and load to work not at parsing time but execution time (kind of PHP's include/require directives).
