How flex parses the flex program code.

pan64 · 02-01-2024, 11:35 AM

obviously make parse does not work, there is a missing r at the end: make parser is the right syntax

NevemTeve · 02-01-2024, 11:57 AM

@OP please go back to post #13 -- that wasn't the actual command and error massage, was it?

ajiten · 02-01-2024, 04:55 PM

Quote:

Originally Posted by NevemTeve

@OP please go back to post #13 -- that wasn't the actual command and error massage, was it?

Sorry, the command was wrong. Though, now on (having run the 3 lines of commands in the 'earlier' makefile) the error is not there.

Code:

$ bison -o parser.c -Hparser.h parser.y
$ flex -o lexpars.c lexpars.flex
$ cc -m64 -g -W -Wall -DYYDEBUG -m64 -g -L/usr/local/lib64 -Wl,-rpath,/usr/local/lib64 parser.c lexpars.c   -o parser
parser.y: In function ‘main’:
parser.y:392:9: warning: implicit declaration of function ‘yyset_debug’ [-Wimplicit-function-declaration]
  392 |         yyset_debug(1);
      |         ^~~~~~~~~~~
parser.y:387:9: warning: unused variable ‘token’ [-Wunused-variable]
  387 |     int token = 0;
      |         ^~~~~
lexpars.c:1281:16: warning: ‘input’ defined but not used [-Wunused-function]
 1281 | #else
      |                ^
lexpars.c:1238:17: warning: ‘yyunput’ defined but not used [-Wunused-function]
 1238 |
      |                 ^

And, if run the 'make parser' command, instead get the response.

Code:

$ make parser
make: 'parser' is up to date.

NevemTeve · 02-02-2024, 12:12 AM

Note1: you are allowed to copy+paste the relevant lines from your terminal-window, you don't have to annoy us with screen-shots.

Note2: you might be one 'git pull' late, but that doesn't matter much.

So you have a working executable, and you have the test files so you can try them

Code:

./parser.exe sample01.txt
type_specifier -> INT
type_specifier -> INT
parameter_list -> type_specifier ID
type_specifier -> INT
parameter_list -> parameter_list COMMA type_specifier ID
variable -> ID
factor -> variable
unary_expression -> factor
term -> unary_expression
simple_expression -> term
ADDOP+
variable -> ID
factor -> variable
unary_expression -> factor
term -> unary_expression
simple_expression -> simple_expression ADDOP(+) term
rel_expression  -> simple_expression
expression -> logic_expression
statement -> RETURN expression SEMICOLON
statements -> statement
compound_statement -> LCURL statements RCURL
func_definition -> type_specifier ID LPAREN parameter_list RPAREN compound_statement
program -> unit
start -> program

ajiten · 02-03-2024, 02:17 AM

Quote:

Originally Posted by NevemTeve

Note1: you are allowed to copy+paste the relevant lines from your terminal-window, you don't have to annoy us with screen-shots.

Note2: you might be one 'git pull' late, but that doesn't matter much.

So you have a working executable, and you have the test files so you can try them

Code:

./parser.exe sample01.txt
type_specifier -> INT
type_specifier -> INT
parameter_list -> type_specifier ID
type_specifier -> INT
parameter_list -> parameter_list COMMA type_specifier ID
variable -> ID
factor -> variable
unary_expression -> factor
term -> unary_expression
simple_expression -> term
ADDOP+
variable -> ID
factor -> variable
unary_expression -> factor
term -> unary_expression
simple_expression -> simple_expression ADDOP(+) term
rel_expression  -> simple_expression
expression -> logic_expression
statement -> RETURN expression SEMICOLON
statements -> statement
compound_statement -> LCURL statements RCURL
func_definition -> type_specifier ID LPAREN parameter_list RPAREN compound_statement
program -> unit
start -> program

Please tell what you expected in the 3 empty header files, in the project, as you have stated in each of them : 'missing file'. The 3 header files are:
1. ScopeTable.h,
2. SymbolInfo.h,
3. SymbolTable.h.

I assume that for the case of the exercise stated earlier, the the second table would have the information given on the page, i.e.:

Code:

#ifndef _SCANTYPE_H_
#define _SCANTYPE_H_
// 
//  SCANNER TOKENDATA
// 
struct TokenData {
    int  tokenclass;        // token class
    int  linenum;           // line where found
    char *tokenstr;         // what string was actually read
    char cvalue;            // any character value
    int  nvalue;            // any numeric value or Boolean value
    char *svalue;           // any string value e.g. an id
};
#endif

Though the header file can be optionally named: Scantype.h, instead to satisfy the naming convention specified by the web-page.

The name of the file lexpars.flex, should be renamed parser.l; accordingly. Though the contents need be mulled by me still.

NevemTeve · 02-03-2024, 02:59 AM

I really don't understand what are you talking about.

You linked a stackoverflow question: https://stackoverflow.com/questions/...-bison-grammar
That question contains incomplete code, asking for help with debugging.

As you know, only actual executables can be debugged, so I added the missing files.
The result is here: https://github.com/lzsiga/stackoverflow_50821203

And now you bring in some unrelated website I know nothing of.

ajiten · 02-03-2024, 03:52 AM

Quote:

Originally Posted by NevemTeve

I really don't understand what are you talking about.

You linked a stackoverflow question: https://stackoverflow.com/questions/...-bison-grammar
That question contains incomplete code, asking for help with debugging.

As you know, only actual executables can be debugged, so I added the missing files.
The result is here: https://github.com/lzsiga/stackoverflow_50821203

And now you bring in some unrelated website I know nothing of.

Please tell what you expected in the 3 empty header files, in the project, as you have stated in each of them : 'missing file'. The 3 header files are:
1. ScopeTable.h,
2. SymbolInfo.h,
3. SymbolTable.h.

NevemTeve · 02-04-2024, 09:07 AM

You can safely delete these files.